Dissertations / Theses: 'Bycatch'

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Winship, Arliss J. "Estimating the impact of bycatch and calculating bycatch limits to achieve conservation objectives as applied to harbour porpoise in the North Sea." Thesis, St Andrews, 2009. http://hdl.handle.net/10023/715.

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Lawson, Julia Margaret. "Rare seahorses have big implications for small fishes in bycatch." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/50198.

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The incidental capture of marine organisms is a critical area of concern in fisheries management, and despite the dominance of small fishes in bycatch biomass around the globe, we know little about the impacts of bycatch on these small fishes. Here, I focus on one such small fish taxon, the seahorses (Hippocampus spp.). Seahorse populations are typically patchy, and they have a specialized life history that makes them more likely to be vulnerable to overfishing. I assessed the impacts of nonselective gear on seahorses in one country by examining potential impacts for three species in peninsular Malaysia. I also assessed the impacts of seahorse bycatch globally, by synthesizing a global array of studies. For my national analysis, I used data-poor assessment methods to estimate life history parameters for three species of seahorse in peninsular Malaysia (Chapter 2). For my global analysis, I extracted data found in a published and unpublished reports to generate a synthesis of global seahorse bycatch (Chapter 3). Nationally, my findings indicate the potential for overfishing for one species found in the southwest region of the peninsular Malaysia. Globally, my synthesis revealed that all fishing gears obtained seahorses in bycatch, but at very low rates of capture per vessel per day. Across all countries, fishers characterized seahorses as relatively rare in their bycatch and declining in catches. One key finding was that low CPUE scaled up to tens of millions of seahorses obtained globally as bycatch each year. My results address the impacts of bycatch on seahorses and discuss the implications for other small bycaught fish species, especially those that are demersal or rare.
Science, Faculty of
Zoology, Department of
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Reis, Marcelo. "Chondrichthyan Bycatch: Risk Assessment, Spatiotemporal trends and Contributions to Management." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/19985.

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Bycatch is one common aspect of fisheries worldwide and recognized as one of the significant impacts over protected and threatened species, chondrichthyans among them. This thesis aims to help mitigate and provide tools to aid the conservation of chondrichthyans. In the first data chapter I developed a model of risk assessment to quantify relative vulnerability of the group based on spatial overlap of natural distributions and fishing events and related to the species resilience. In this study I used commercial fisheries data provided by the Australian Fisheries Management Authority and applied the method to bycatch chondrichthyans and target species. Results were consistent with IUCN status of the species, including cases with regional differences from global status. In the second data chapter, spatial and seasonal distribution of chondrichthyan bycatch events in southern and eastern Australia were analysed. Results indicate differences in rates between gears and also the importance of oceanographic factors to bycatch ratio as well to catch per unit of effort whilst diversity is more influenced by gear type. The spatial analyses also indicated hotspots for bycatch in the Great Australian Bight and Bass Strait. In the third data chapter, I estimated the age, growth and reproductive parameters of the Eastern Fiddler Ray Trygonorrhina fasciata and the Sydney Skate Dipturus australis, two endemic species often caught as bycatch. Age estimates, based on vertebrae bands, were used to calculate growth parameters, which were similar to related species. Moreover, based upon the somatic and gonad indexes, reproductive biology information of these species is provided. In the fourth data chapter I describe the diet and estimated trophic levels of these batoids. Results indicated a diet consisting largely of crustaceans and place the species within the range of trophic level for closest relatives and support their status as mesopredators on the region.

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Milleville, Kelli A. "Twine-Top Modifications of Sea-Scallop Dredges: Reducing Yellowtail-Flounder Bycatch." W&M ScholarWorks, 2008. https://scholarworks.wm.edu/etd/1539617874.

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Petersen, Samantha Lara. "Understanding and mitigating vulnerable bycatch in southern African longline and trawl fisheries." Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/19137.

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Over the past decade there has been global concern about the bycatch of seabirds, turtles and sharks in fishing operations, in particular longline and trawl fisheries, which have been widely held responsible for their declining population s and threatened conservation status. This thesis addresses the issue of bycatch in a holistic manner, taking into account that species, whether they be target or non-target, do not exist in isolation from each other and their environment. South African fisheries incidentally catch approximately 21 000 seabirds, 165 turtles and 43 000 pelagic sharks per year, including 21 Endangered species. Decreasing CPUE and size-frequency data for Blue Prionace glauca and Short- finned Mako Sharks Isurus oxyrinchus caught in the large pelagic longline fishery suggests exploitation of these species is unsustainable. A decreasing trend in the biomass index was also observed for the Yellow-spotted Catshark Scyliorhinus capensis and the Biscuit Skate Raja. straeleni. An argument for the likelihood of fisheries mortality contributing to the slower than expected turtle population recovery rates is presented, which is supported by results from satellite tracking of Leatherback Turtles Dermochelys coriacea indicating a high degree of overlap with fishing effort. Satellite tracking of Black-browed Thalassarche melanophrys and White-capped T. steadi Albatrosses reveal striking differences in their foraging patterns and presents evidence that Black-browed Albatrosses, in particular, forage to a large extent on natural prey, despite the availability of discards from fishing vessels in the Benguela. Therefore, given the high albatross mortality in the trawl fishery, the benefit of a management decision to limit discarding as a mitigation measure is likely to outweigh the disadvantage of reduced food supply. Reducing bycatch is dependent on the development of effective and relatively inexpensive methods which do not impact on target catches and/or other vulnerable species. In the demersal longline fishery, two methods of optimising line sink rates to reduce seabird bycatch were investigated: increasing mass of weights and decreasing the spacing between weights. This study indicated that while the target species is unlikely to be affected by increased weighting, other vulnerable species of fish and sharks may be affected. Other mitigation experiments investigated line sinking rates and the use of circle hooks in pelagic longline fisheries. The implications of night setting on Swordfish Xiphias gladius catches, fishery closure during full moon and the appropriateness of the international standard 5% fin to trunk ratio for the South African fishery, were also investigated. Lastly, the spatial and temporal overlap of catches of seabirds, turtles and sharks were investigated through a conservation planning exercise using MARXAN and potential areas for closure identified.

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Rollinson, Dominic Paul. "Understanding and mitigating seabird bycatch in the South African pelagic longline fishery." Doctoral thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/25500.

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Seabirds are considered one of the most threatened groups of birds in the world. They face additional mortality both on their breeding islands from introduced predators and at sea by fishing fleets, as fisheries bycatch, as well as other human impacts. Seabird bycatch has negatively affected many seabird populations worldwide, with trawl, gillnet and longline fisheries considered the most destructive to seabird populations. Seabird bycatch from trawl and gillnet fisheries has been significantly reduced in recent years, but large numbers of seabirds are still killed annually by longline fisheries. Of the two types of longline fisheries (demersal and pelagic), pelagic longlining is considered the most harmful to seabirds as lines remain closer to the surface for longer periods than demersal longlining, and it is harder to weight lines to ensure rapid sinking beyond the depth they are accessible to birds. Seabirds are killed when they swallow baited hooks and consequently drown. Despite the large number of studies investigating seabird bycatch from pelagic longline fisheries, there remain gaps in our understanding of seabird bycatch from pelagic longline fisheries. This thesis addresses some of these knowledge gaps and makes recommendations as to how seabird bycatch from pelagic longliners can be reduced at both a local and global scale. Chapters 2 and 3 investigate the factors affecting seabird bycatch from pelagic longliners off South Africa, provide a summary of seabird bycatch from the fishery for the period 2006–2013 and quantify the structure of seabird assemblages associated with pelagic longline vessels off South Africa. This was achieved by analysing seabird bycatch data collected by fisheries observers as well as data from sea trials onboard pelagic longliners. Seabird bycatch by pelagic longliners off South Africa over the 8-year study period has been significantly reduced from the 8-year period (1998–2005), mainly driven by a significant reduction in seabird bycatch rates from foreign-flagged vessels, which are responsible for c. 80% of fishing effort off South Africa. Seabird bycatch rates from South African vessels still remain high, four times higher than the interim national target of < 0.05 birds per 1000 hooks. The species composition of seabird bycatch off South Africa is best explained by an understanding of the structure of the seabird assemblage associated with longline vessels. For most species, bycatch and attendance ratios were similar, but for some species such as shy-type and black-browed albatrosses there were large mismatches, likely caused by differences in foraging behaviour and foraging dominance hierarchies. In Chapters 4 and 5 the foraging ecology of the most commonly recorded bycatch species off South Africa, the white-chinned petrel (Procellaria aequinoctialis), is investigated. An understanding of the foraging ecology of commonly recorded bycatch species enhances our understanding of seabird bycatch and helps to improve the design of current and future mitigation measures. The year-round movements of white-chinned petrels from Marion Island were investigated with Global Location Sensors (GLS loggers) and GPS loggers. Adult white-chinned petrels undertake only limited east-west movements of, with all birds remaining between southern Africa and Antarctica. These results strengthen the theory that there is limited spatial overlap year-round between white-chinned petrel populations from South Georgia, the southern Indian Ocean islands and New Zealand sub-Antarctic islands, suggesting that these populations can be managed as separate stocks. The diving behaviour of white-chinned and grey petrels (P. cinerea), another common bycatch species in Southern Ocean longline fleets, were examined with the use of temperature-depth recorders (TDRs), deployed on birds from Marion Island and Gough Island. My study was the first to analyse TDR dive data from any Procellaria petrel, and recorded them reaching maximum dive depths of 16 and 22 m, respectively. Current best practise suggests that baited hooks be protected to a depth of 5 m by bird-scaring lines, but my results suggest this depth should be increased to at least 10 m. Although line weighting is a proven mitigation measure to reduce seabird bycatch from pelagic longliners, fishers have concerns that it will compromise fish catches, crew safety and operational efficiency. In Chapter 6 I analyse line weighting data from trials onboard three pelagic longline vessels, to address the concerns of fishermen. My results show that sliding leads can be incorporated into pelagic longline fisheries without compromising fish catch, crew safety or operational efficiency. I thus recommend that sliding leads be used on pelagic longline vessels fishing off South Africa. By incorporating studies investigating the factors affecting seabird bycatch, seabird foraging ecology and the efficacy of seabird bycatch mitigation measures, my thesis has broadened our understating of seabird bycatch from pelagic longliners and makes meaningful recommendations to further reduce bycatch, both locally and globally. Although seabird bycatch rates have declined off South Africa, through the use of a number different mitigation measures, they still remain higher than the South African national target and thus more work is needed to achieve this target. To reduce seabird bycatch from pelagic longliners to acceptable levels, studies from the world's various longline fleets needs to be considered and improved upon, with seabird conservationists and fishermen working together to achieve this goal.

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Bochini, Gabriel Lucas. "Composição, abundância e diversidade de Brachyura (Crustacea Decapoda) acompanhante da pesca de arrasto do camarão sete-barbas no Litoral sul de São Paulo. /." Botucatu, 2016. http://hdl.handle.net/11449/148833.

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Orientador: Rogerio Caetano Costa
Resumo: Os objetivos deste estudo foram: 1) investigar a composição taxonômica de Brachyura; 2) avaliar a assembleia destes por meio dos índices ecológicos; 3) verificar a relação das espécies em função dos fatores abióticos; e 4) analisar se há sincronismo entre os períodos reprodutivos das espécies mais abundantes em comparação ao camarão alvo da pesca X. kroyeri. Foram realizadas coletas mensais (julho/12 a junho/14) na região marinha (4 estações amostrais: E1, E2, E3 e E4) e na região de Mar Pequeno (MP) (3 estações amostrais: E5, E6, e E7), com um barco camaroeiro equipado com redes “double rig”. Foram calculados o índice de Shannon (H), a equidade (J’) a Riqueza (S) e o Índice de Valor Ecológico (IVE), e avaliou-se as relações entre espécies X estações amostradas e entre regiões X períodos (análise de cluster). A temperatura variou entre as estações do ano (maior no verão e menor no inverno), mas não variou entre as regiões amostradas. Já a salinidade variou entre as regiões, sendo menor no MP. O sedimento foi composto pela mistura de areia fina e muito fina. O teor de matéria orgânica foi similar entre as estações de coleta, com exceção de E4 e E5. A concentração média de clorofila variou entre as estações do ano, sendo maior no verão e menor no inverno. Um total de 19.501 indivíduos de Brachyura foi coletado, representados por 25 espécies, 18 gêneros e 13 famílias, sendo elas: Portunidae, Aethridae, Leucosiidae, Epialtidae, Menippidae, Pinnotheridae, Inachoididae, Dromiidae, ... (Resumo completo, clicar acesso eletrônico abaixo)
Doutor

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Mackay, Alice I. "An investigation of factors related to the bycatch of small cetaceans in fishing gear." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/1888.

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The bycatch of cetaceans in fishing gear is considered to be one of the biggest conservation threats to these species. Gear modifications have the potential to reduce these bycatches in global fisheries but there is little available information on how such modifications may change the fishing performance of gear, or indeed the behavior of cetaceans interacting with fishing gear. Generalized linear models (GLMs) were used to identify factors related to cetacean bycatches in UK bottom set gillnets. Rigged net height had a significant positive relationship with harbour porpoise (Phocoena phocoena) bycatch in ICES Area VII suggesting that lowering the profile of gillnets may have the potential to reduce bycatch rates. Modifications to gillnets, such as changing the amount of floatation or increasing the density of the meshes, were found to have significant effects on the active fishing heights of these nets. However, results from a bycatch mitigation trial in Argentina showed that the reduced fishing profile of one experimental net did not result in a concurrent reduction in the bycatch rate of Franciscana dolphins (Pontoporia blainvillei). While there was no significant difference in the rate, length or intensity of harbour porpoise encounters in the presence or absence of gillnets, the proportion of fast echolocation click trains were significantly higher when a net was present, indicating that porpoises either increased acoustic inspection of the net or foraging in the vicinity of the net. An analysis of underwater video footage collected inside trawl nets in an Australia fishery showed that bottlenose dolphins (Tursiops sp.) were present inside nets more frequently than they were caught and were actively foraging inside these nets. The orientation of dolphins inside these nets indicates that the current design of excluder devices used in this fishery could be improved to further reduce bycatch rates.

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Rice, Patrick Hays. "Factors Affecting the Catch of Target and Bycatch Species During Pelagic Longline Fishing." Scholarly Repository, 2008. http://scholarlyrepository.miami.edu/oa_dissertations/85.

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Recent evidence suggests that overfishing of large predatory fishes has resulted in substantial population declines and pelagic longline (PLL) fishing is a major contributor. The primary objective of this dissertation is understanding factors that affect the interactions between marine fish PLL fishing. These factors are important to determine vulnerability of bycatch and target species, especially when PLL catch and effort data are used to estimate stock abundance. Chapter 1 reviews 107 publications/reports on this topic. Results indicate that accurate characterization of PLL gear performance requires empirical measurement of horizontal and vertical gear movement; and pop-up satellite tags (PSATs) are best suited for quantifying pelagic fish vertical habitat use if: (i) sampling resolution and data storage are not a function of tracking duration and (ii) substantial monitoring durations are employed. This review documents the current state of knowledge for these factors and guidance for future research. In Chapter 2, hook time-at-depth was monitored for commercial PLL sets targeting swordfish, Xiphias gladius. Temperature-depth recorders (TDRs) were deployed at the hook, systematically along the entire gear length. Results indicated that: (i) hook depth predictions based on catenary geometry drastically overestimated actual fishing depths and (ii) using catenary geometry fails to capture within- and among-set variability, potentially resulting in biased stock assessments. Chapter 3 used temperature-depth data from PSATs on swordfish and blue marlin (Makaira nigricans) and similar data from TDR monitored near-surface and deep PLL fishing to determine the diel probability of these species encountering PLL hooks. Results indicated that blue marlin and swordfish inhabit surface waters at night with similar probability of encountering PLL hooks but may have different vulnerabilities due to temporal separation in feeding with blue marlin preferring daytime and twilight and swordfish preferring nighttime. Therefore, reducing fishing during daylight hours may reduce blue marlin bycatch during PLL targeting swordfish. Chapter 4 alternated non-offset and 10° offset circle hooks during PLL fishing and compared the relative performance on catch rates, percent mortality, and deep hooking percentage. Results indicated that 10° offset circle hooks can reduce fishing efficiency and conservation benefits commonly associated with circle hooks.

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Richter, Christoph. "Harbour porpoise and people : strategies for bycatch reduction in the Bay of Fundy /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ36173.pdf.

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Vieira, Feitosa Caroline. "Biologia populacional de Pomacanthus paru (Teleostei: Pomacanthidae) e análise da sustentabilidade de captura do bycatch de peixes ornamentais." Universidade Federal de Pernambuco, 2009. https://repositorio.ufpe.br/handle/123456789/8180.

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Made available in DSpace on 2014-06-12T22:58:01Z (GMT). No. of bitstreams: 2 arquivo1443_1.pdf: 3633149 bytes, checksum: 40243e6f486c59abff57d572e11594dd (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2009
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Pomacanthus paru tem grande importância para o aquarismo brasileiro, além de ser a segunda espécie marinha mais exportada desde 2000. Os objetivos desta pesquisa foram os seguintes: (a) descrever a biologia reprodutiva e determinar a idade e o crescimento de P. paru, (b) analisar a diversidade genética de P. paru e P. arcuatus a partir do DNA mitocondrial, (c) registrar as espécies de peixes ornamentais capturadas como bycatch através da pesca com armadilhas e propor uma metodologia para determinar a sustentabilidade de captura das principais espécies ornamentais marinhas no Brasil. Amostragens semanais foram realizadas durante o período de março 2006 a fevereiro 2007. Os exemplares menores de 15 cm foram comprados de coletores de peixes ornamentais. Os peixes foram medidos, pesados, e as gônadas e os otólitos foram removidos. Amostras de músculo e do fígado foram armazenadas para o estudo genético. A região 16S rDNA foi amplificada e sequências do ADN mitocondrial foram utilizadas para a análise dos haplótipos. Para a proposição da metodologia de sustentabilidade de captura, cada espécie foi avaliada segundo dois grupos de critérios: (1) vulnerabilidade relativa à captura pelas armadilhas; (2) resiliência da população relacionada à mortalidade devido à pressão pesqueira. No total, 236 indivíduos foram analisados, sendo 139 fêmeas, 86 machos e 11 que não tiveram o sexo definido. P. paru é uma espécie gonocorística, que se reproduz ao longo do ano, com as fêmeas apresentando dois picos de desova (Fevereiro-Março/Setembro-Outubro). As fêmeas foram mais abundantes em todos os meses, exceto em outubro. O L50 é atingido aos 30 cm para as fêmeas e 35 cm para os machos. A idade dos indivíduos amostrados de P. paru variou de 1 a 27 anos. P. paru atinge o comprimento máximo lentamente e tem um longo ciclo de vida. Para P. paru seis haplótipos foram encontrados, enquanto em P. arcuatus apenas um, incluindo os espécimes do Caribe. Foram registradas como bycatch, 19 espécies pertencentes a 10 famílias. As espécies cujas capturas foram menos sustentáveis foram Holacanthus tricolor, H. ciliaris, Chaetodon striatus e P. paru. O manejo de P. paru deve incluir medidas baseadas no tamanho de primeira maturação sexual, bem como nos parâmetros de crescimento aqui estabelecidos. Os resultados relacionados à genética representam um primeiro passo para se compreender as estruturas populacionais de espécies tão próximas filogenética e ecologicamente como P. paru e P. arcuatus. A nova metodologia aqui proposta deverá ser uma ferramenta útil e alternativa para o manejo e avaliação da sustentabilidade de captura das espécies oriundas de pescarias multi-específicas, com poucos dados disponíveis e que ocorrem em áreas de alta riqueza, como os recifes

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Allen, Simon. "Fishery-impacted bottlenose dolphins of north-western Australia: Bycatch patterns, genetic status and abundance." Thesis, Allen, Simon (2015) Fishery-impacted bottlenose dolphins of north-western Australia: Bycatch patterns, genetic status and abundance. PhD thesis, Murdoch University, 2015. https://researchrepository.murdoch.edu.au/id/eprint/27047/.

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The incidental capture of cetaceans in fisheries threatens several species with extinction and represents a global conservation challenge. In order to assess the impacts of bycatch on dolphins in a north-western Australian trawl fishery, I (i) examined bycatch reported in skippers’ logbooks and independent observer data; (ii) applied genetic methods to estimate dolphin population structure and connectivity; and (iii) conducted an aerial survey to estimate dolphin abundance across the fishery, simultaneously undertaking boat-based photo-identification to infer fidelity to the fishery. From 2003-2009, between 180 and 366 dolphins were caught across all management areas, depths and seasons. Independent observers reported more than double the dolphin bycatch reported in skippers’ logbooks. Significant predictors of dolphin bycatch were fishing vessel, time-of-day and whether nets included Bycatch Reduction Devices (BRDs). Genetic evidence showed one panmictic population of trawler-associated common bottlenose dolphins (Tursiops truncatus), but isolation from all adjacent, coastal populations of Indo-Pacific bottlenose dolphins (T. aduncus). Abundance was estimated at 2,000-3,000 T. truncatus across 25,880 km2. While the lack of correction factors for availability bias mean this is likely an underestimate, it is lower than previously thought. Trawler-associated individuals were photographically and genetically matched over periods of days to years. Recent skippers’ logbook data suggest dolphin bycatch rates have increased since the BRDs were introduced. These results indicate that (i) only a considerable reduction in trawling effort is likely to reduce dolphin bycatch; (ii) the impacted population does not recruit from the adjacent coastal populations; and (iii) the number of dolphins interacting with trawlers is fewer than expected. The chronic bycatch of this protected species may affect the dolphin population’s conservation status. As a consequence, the classification of acceptable limits of bycatch requires revision in light of these first estimates of the abundance and fidelity of bottlenose dolphins interacting with the Pilbara Trawl Fishery.

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Beerkircher, Lawrence R. "Manuscript 1: Elasmobranch Bycatch Observed on Pelagic Longlines Off the Southeastern U.S. Coast, 1992-1997." NSUWorks, 2000. http://nsuworks.nova.edu/occ_stuetd/314.

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Data collected by fisheries observers aboard U.S. pelagic longline vessels were examined to quantify and describe elasmobranch bycatch off the southeastern U.S. coast (22° - 35° N, 71° - 82° W). From 1992 to 1997, 608 "sets" or gear deployments were observed which resulted in the capture of 2649 elasmobranchs (17.5 percent of the total catch). Of the 21 elasmobranch species observed, silky sharks, Carcharhinus falciformis, were numerically dominant (34.4%) followed by dusky, C. obscurus (16.3%), blue, Prionace glauca (8.9%), unidentified sharks (6.4%), tiger, Galeocerdo cuvier (5.9%), and scalloped hammerhead, Sphyrna lewini (5.7%). The catch status of the animal (alive or dead) when the gear was retrieved varied widely depending on the species, with high mortalities seen for the commonly caught silky and dusky sharks and low mortalities for rays, blue sharks, and tiger sharks. Discard percentages depended mostly on the marketability of the species, ranging from low discards (20.4 %) for shortfin mako, Isurus oxyrhinchus, to high discards for blue (99.5 %), tiger (96.7 %), and rays (100 %). Percentages of live and dead discards also varied considerably among species. Analysis of variance indicated significant catch rate differences among seasons for silky, dusky, blue, oceanic whitetip (C. longimanus), sandbar (C. plumbeus), and shortfin mako sharks. Mean fork lengths indicated the majority of the observed bycatch, regardless of species, was immature, and significant seasonal variation in fork length was found for several species including silky, dusky, blue, night (C. signatus), and oceanic whitetip sharks. While sex ratios overall were relatively even, blue and tiger shark catches were dominated by females. Only silky sharks showed significant seasonal sex ratio variation, with a higher proportion of males observed in the winter. Bootstrap methods were used to generate yearly mean catch rates (catch per unit effort) and 95 % confidence limits. Catch rates were in turn used to generate an overall estimate of the numbers of elasmobranchs discarded dead and alive during 1992-1997. These estimates predict 38,775 (18,780 and 63,751, lower and upper 95 % confidence limits) and 31,859 (13,837 and 56,712, lower and upper 95 % confidence limits) sharks were discarded alive and dead, respectively, during this time period. Possible implications of the results of this study for shark fishery management are discussed for the most common bycatch species.

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Udoff, Geoffrey. "An Alternate Trawling Method: Reduced Bycatch and Benthic Disturbance Achieved with the Wing Trawling System." ScholarWorks@UNO, 2016. http://scholarworks.uno.edu/td/2217.

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The Wing Trawling System (WTS) was tested as an alternative to traditional shrimp capture methods in the Gulf. Compared to an otter trawl, this trawl was conceived to reduce bycatch, retain shrimp catch, and minimize seafloor disturbance. Through seventy-one paired tows, the WTS was assessed against a standard otter trawl. The WTS was found to reduce bycatch by 63-65% and reduce shrimp catch by 30-35%. Additionally, I measured the depth of the scars produced by both trawls and quantified the turbidity of the plumes behind them. The scars left by the WTS and the otter trawl were between 9.9 cm-13.6 cm. The turbidity behind the WTS was 18.6 NTU, while the turbidity behind the otter trawl was 206.8 NTU. In conclusion, the WTS offers an alternative to an otter trawl that reduces bycatch and the impact trawling has on the seafloor but results in a significant amount of shrimp loss.

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Graham, Larissa Joy. "Bycatch associated with a horseshoe crab (Limulus polyphemus) trawl survey: identifying species composition and distribution." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/34660.

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Horseshoe crabs (Limulus polyphemus) have been harvested along the east coast of the United States since the 1800s, however a Fishery Management Plan (FMP) was only recently created for this species. To date, there have not been any studies that have attempted to identify or quantify bycatch in the horseshoe crab trawl fishery. A horseshoe crab trawl survey was started in 2001 to collect data on the relative abundance, distribution, and population demographics of horseshoe crabs along the Atlantic coast of the United States. In the present study, species composition data were collected at sites sampled by the horseshoe crab trawl survey in 2005 and 2006. Seventy-six different taxa were identified as potential bycatch in the horseshoe crab trawl fishery. Non-metric multidimensional scaling (NMS) was used to cluster sites and identify the spatial distribution of taxa. Sites strongly clustered into distinct groups, suggesting that species composition changes spatially and seasonally. Species composition shifted between northern and southern sites. Location and bottom water temperature explain most of the variation in species composition. These results provide a list of species that are susceptible to this specific trawl gear and describe their distribution during fall months throughout the study area. Identifying these species and describing their distribution is a first step to understanding the ecosystem-level effects of the horseshoe crab trawl fishery.
Master of Science

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Li, Yan. "Investigating ecosystem-level effects of gillnet bycatch in Lake Erie: implications for commercial fisheries management." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/76836.

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Lake Erie supports one of the world's largest freshwater commercial fisheries. Bycatch has become a concern in current fisheries management. This study focused on four species in Lake Erie that include two major commercial and recreational species, walleye (Sander vitreus) and yellow perch (Perca flavescens); an invasive species, white perch (Morone americana); and an endangered species, lake sturgeon (Acipenser fulvescens). The analyses were based on two datasets, the Partnership Index Fishing Survey (PIS) data and the commercial gillnet logbook data. The bycatch of walleye, yellow perch and white perch was predicted by a delta model developed on the PIS data. Discards were estimated as the difference between predicted bycatch and landed bycatch. Results highlighted bycatch and discard hotspots for these three species that have great management implications. Three classification tree models, a conditional inference tree and two exhaustive search-based trees, were constructed using the PIS data to estimate the probability of obtaining lake sturgeon bycach under specific environmental and gillnet fishing conditions. Lake sturgeon bycatch was most likely to be observed in the west basin of Lake Erie. The AdaBoost algorithm was applied in conjunction with the generalized linear/additive models to analyze catch rates of walleye, yellow perch and white perch. Three- and five-fold cross-validations were conducted to evaluate the performance of each candidate model. Results indicated that the Delta-AdaBoost model yielded the smallest training error and test error on average. I recommend the Delta-AdaBoost model for catch and bycatch analyses when data contain a high percentage of zeros.
Master of Science

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17

Walmsley, Sarah Ann. "The assessment and management of bycatch and discards in the South African demersal trawl fishery." Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1005071.

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Over the past few decades it has become recognised that an ecosystem approach is required to manage world fisheries. Management strategies must ensure that non-target (bycatch) as well as target catches are sustainable. To achieve this, detailed commercial catch and biological information is required. The composition of catches made by trawlers operating off the south and west coasts of South Africa was investigated. Distinct fishing areas were identified on each coast, based on target species and fishing depth. Catch composition differed markedly among the areas defined. Although hake Merluccius sp. dominated South Coast catches, a large proportion of the catch was composed of bycatch. On the West Coast, hake dominated catches and this domination increased with increasing depth. On both coasts approximately 90% of the observed nominal catch was processed and landed. Estimates of annual discards suggested that the fishery discarded 38 thousand tons of fish per annum (16% of the nominal trawl catch). The data also indicated that hake discarding, the capture of linefish and the increased targeting of high value species might be cause for concern. Spatial analysis indicated that a variety of factors such as trawling position, catch size and catch composition affects bycatch dynamics. The monkfish Lophius vomerinus is a common bycatch species that has been increasingly targeted by demersal trawlers. This study showed that L. vomerinus is a slow-growing, long-lived species (West Coast males L∞ = 68.50cm TL, t₀ = -1.69yr, K = 0.10yr⁻¹; West Coast females L∞ = 110.23cm TL, t₀ = -1.54yr, K = 0.05yr⁻¹; South Coast sexes combined L∞ = 70.12cm TL, t₀ = - 0.80yr, K = 0.11yr⁻¹), that matures at approximately 6 years of age. These traits could have serious management implications for the species. Per-recruit analysis suggested that the stock might be overexploited, although further investigation is required to confirm this. Solutions were suggested for each of the concerns raised, taking cognisance of the differences observed between the South and West Coasts and the economic dependence of South Coast companies on bycatch. The needs of future research were considered.

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18

Scott-Denton, Elizabeth. "U.S. southeastern shrimp and reef fish resources and their management." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1676.

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19

Weidner, Tiffany A. "Combined Gut Content-Stable Isotope Trophic Analysis and Satellite Tagging of the Pelagic Stingray Pteroplaytrygon violacea (Bonaparte, 1832) from the Western North Atlantic Ocean." NSUWorks, 2014. http://nsuworks.nova.edu/occ_stuetd/10.

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The pelagic stingray, Pteroplatytrygon violacea, is a bycatch species in the global pelagic longline fishery. However, little research has been conducted on its basic biology, including prey composition, trophic positioning, and habitat utilization. Descriptions of the habitat utilization have largely been through indirect analyses of catch rates in commercial fisheries, which also provided no information on actual behaviors. The first chapter of this thesis will describe the habitat utilization and behavior of four individual pelagic stingrays using electronic tagging technology. Prior diet descriptions were hampered, in part, by low sample sizes and accordingly provided little information on the ecological interactions of these animals. Similarly, the second chapter of this thesis will therefore provide a new diet description for the pelagic stingray using a combined analysis of traditional stomach contents with stable isotope values, thereby addressing both ingestion and assimilation. A more robust study of the trophic dynamics of the pelagic stingray, in conjunction with the description of its habitat utilization, will provide a better understanding of its role within the pelagic ecosystem. Ultimately, the goal is to obtain knowledge of the less economic species with good science so when management approaches shift from species-specific to ecosystem based, the transition will already have known information to change efficiently.

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20

Camargo, Tavani Rocha. "Bioprospecção de compostos antioxidantes na fauna acompanhante da pesca demersal /." Jaboticabal, 2020. http://hdl.handle.net/11449/192721.

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Orientador: Wagner Cotroni Valenti
Resumo: Nos últimos anos, a fauna acompanhante da pesca camaroeira vem sendo alvo de estudos por ser um dos fatores do grande impacto ambiental causado pela pesca de arrasto. Em contrapartida, esse rejeito de pesca pode ter propriedades funcionais e bioativas, como peptídeos antioxidantes, que poderiam agregar valor a esse rejeito e se tornar um produto de interesse para as indústrias alimentícias. Assim, o presente estudo visou investigar a atividade antioxidante dos hidrolisados proteicos obtidos dos animais mais abundantes da fauna acompanhante e microencapsular esses hidrolisados para agregar valor à este material normalmente descartado. Os resultados demonstram que a hidrólise enzimática, utilizando as enzimas comerciais Alcalase 2.4 L® e Protamex®, é um método eficiente para liberar peptídeos de interesse econômico nas duas espécies mais abundantes de peixes (Micropogonias furnieri e Paralonchurus brasilensis) e nas duas mais abundantes de crustáceos (Callinectes ornatus e Hepatus pudibundus). A hidrólise liberou peptídeos com atividade antioxidante em todas as amostras analisadas, submetidas às duas enzimas testadas. A coacervação complexa e subsequente microencapsulação por spray-drying mostrou-se eficiente para proteger a atividade antioxidante desses hidrolisados proteicos. Assim, os resultados fornecem evidências para o potencial uso dos hidrolisados das espécies analisadas como ingrediente funcional ou nutracêutico na indústria alimentícia.
Abstract: In recent years, the bycatch of shrimp fishing has been the subject of studies as it is one of the factors of the great environmental impact caused by trawling. However, this bycatch can have functional and bioactive properties, such as antioxidant peptides, which could add value to this reject and become a product of interest to the food industries. Thus, the present study aimed to investigate the antioxidant activity of protein hydrolysates obtained from the most abundant animals of the bycatch and to microencapsulate these hydrolysates to add value to this normally discarded material. The results demonstrate that enzymatic hydrolysis, using the commercial enzymes Alcalase 2.4 L® and Protamex®, is an efficient method to release peptides of economic interest in the two most abundant species of fish (Micropogonias furnieri and Paralonchurus brasilensis) and in the two most abundant crustaceans (Callinectes ornatus and Hepatus pudibundus). Hydrolysis released peptides with antioxidant activity in all samples analyzed, submitted to the two enzymes tested. Complex coacervation and subsequent microencapsulation by spray-drying proved to be efficient to protect the antioxidant activity of these protein hydrolysates. Thus, the results provide evidence for the potential use of hydrolysates of the analyzed species as a functional or nutraceutical ingredient in the food industry.
Doutor

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21

Alfaro, Shigueto Joanna Olga Gissella. "Ecology and conservation of sea turtles in Peru." Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/3472.

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Some of the key elements to assess the status of any wildlife population in a given geographical area are the levels of recruitment, survival and mortality. Whilst most of the information on marine turtles has been obtained from nesting sites, turtles spend most of their lives at sea. The conservation status of marine turtles in the southeast Pacific is poorly documented. This is particularly true for countries like Peru, where nesting events are very rare, although five species of turtles from populations from all over the Pacific basin, use these waters as foraging grounds. Little information exists on the threats to turtle populations in foraging areas or the magnitude of these impacts. Small-scale fisheries are a globally important economic activity serving as a source of food and employment for ca. 1 billion people; however we show that they also have serious impacts on marine turtle populations from all over the Pacific basin in the form of incidentally captured marine turtles. The five chapters that constitute this thesis are intended to increase our understanding of small-scale fisheries impacts on this taxon during their aquatic life stages. This work focuses on describing these fisheries, their impacts on marine turtles and proposes methodologies to monitor and assess the level of bycatch from small-scale fisheries. We also discuss alternative ways to prevent fisheries interactions and promote the involvement of artisanal fishermen in the southeast Pacific in implementing conservation solutions.

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22

VÉRAS, Dráusio Pinheiro. "Pesca e Historia Natural da Raia-roxa, Pteroplatytrygon violacea (Bonaparte, 1832), No Atlântico Ocidental." Universidade Federal de Pernambuco, 2012. https://repositorio.ufpe.br/handle/123456789/12176.

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CNPq
A raia-roxa, Pteroplatytrygon violacea (Bonaparte, 1832), é a única espécie da família Dasyatidae no ambiente pelágico. O objetivo geral do presente trabalho consistiu em agregar informações sobre a espécie, principalmente no que se refere a sua pesca, seu hábito alimentar, aspectos reprodutivos, distribuição, abundância relativa e preferências de uso do habitat no Oceano Atlântico Ocidental. Para determinar seu hábito alimentar, os estômagos de 106 espécimes foram analisados (69 machos, 26 fêmeas e 11 sem informação de sexo). A importância de cada item alimentar na dieta foi obtida pelo Índice de Importância Relativa (IIR). Foram observados teleósteos, cefalópodes, crustáceos e outras presas que incluíam tunicados, pterópodes e heterópodas. As observações sugerem que a P. violacea altera seus itens alimentares de acordo com sua localização geográfica e também mostra como a espécie, apesar de pertencer à família Dasyatidae, é adaptada ao ambiente pelágico. Os hábitos reprodutivos desta espécie são pouco conhecidos. Estudamos a sua biologia reprodutiva, examinando um total de 480 espécimes, 188 fêmeas (39,2%) e 292 machos (60,8%), e proporção sexual de 1,5 macho: 1 fêmea, capturados na pesca de espinhel comercial entre outubro de 2005 e março de 2010. Tamanhos, medidos pela largura do disco (LD), variaram de 28,0-66,0 cm para fêmeas e de 34,0-59,6cm para os machos. Fêmeas foram classificadas como juvenil (n = 42; 22,7%); em maturação (n = 67; 36,2%); pré-ovulatória (n = 28; 15,1%); prenhe estágio 1 (n = 17; 9,2%); prenhe estágio 2 (n = 13; 7,0%); prenhe estágio 3 (n = 2; 1,1%); pós-parto (n = 6; 3,2%) e repouso (n = 10; 5,4%). Fêmeas grávidas em estágios 1-3 (n =32, 17,3%) variaram entre 48,0-60,0cm LD. O tamanho da primeira maturação sexual foi estimado em 50,0cm LD para fêmeas e 42,0cm CD para os machos. A fecundidade do ovário, considerando-se apenas folículos maiores do que> 0,5 cm de diâmetro, variou de 1-17 folículos/fêmea e a fecundidade uterina de embriões em fêmeas prenhes em estágios 2 e 3 variou 1-5 embriões/fêmea. A proporção sexual entre os embriões foi igual (0,9 machos: 1 fêmea) e o tamanho ao nascer foi próximo de 19,0cm LD. A sua distribuição e abundancia relativa foram determinados analisando os dados de captura e esforço de 6.886 lances de espinhel, distribuídos em uma ampla área do Atlântico Ocidental, variando de 15°N e 40°S de latitude e a partir de 010°E a 050°W de longitude, o esforço de pesca atingiu o máximo de 1.200.000 anzóis e a área com a maior concentração de esforço foi localizado entre 5°N-25°S de latitude e 020°-040°W de longitude. A distribuição espacial do esforço de pesca por trimestre mostrou semelhança no primeiro e segundo trimestres, quando comparado com o terceiro e quarto e mostraram duas áreas distintas, com maior esforço, uma localizada entre 5°N-5°S e 025°-040°W e a segunda entre 10°-25°S e 025°-040°W. A distribuição espacial da CPUE mostrou a ocorrência de duas áreas com altos índices de captura (7,8-18,0 raias/1000 anzóis), um mais ao norte, variando de 10°N-10°S a 030°-045°W e outra mais para o sudeste, variando de 20°-35°S a 040°-045°W. Os valores mais baixos de CPUE foram observados entre 10°-20°S e correspondente a 0,8-1,6 raias/1000 anzóis. A distribuição espacial da CPUE por trimestre mostrou capturas elevadas ocorrendo no primeiro (10°N-00° a 030°-045°W), terceiro (25°-35°S a 040°-045°W) e quarto (05°-10°S a 030°-035°W) trimestres. Na distribuição espacial de machos e fêmeas, nenhuma evidência foi encontrada de uma segregação espacial por sexo, os machos não apresentaram padrão de segregação por estágio de maturidade sexual, as fêmeas apresentaram um leve padrão de segregação dos estádios de maturação sexual. Os dados aqui apresentados mostram que os espécimes de P. violacea capturados no sudoeste do Atlântico equatorial são compostos em sua maioria (98,8% machos e as fêmeas 79,0%) de indivíduos adultos. No presente estudo, para observações do uso do habitat, foi utilizada uma marca eletrônica, Pop-up Archival Tag (PAT). Uma fêmea de raia-roxa, medindo 56,5cm e 48,0cm de largura (LD) e comprimento (CD) de disco respectivamente, capturada em 30 de abril de 2010 foi marcada com uma MiniPAT. O espécime não mostrou nenhum padrão definido de movimento horizontal, movendo-se em muitas direções diferentes em uma área entre 03°-09°N de latitude e 036°-040°W de longitude. Durante os 60 dias com a marca, a raia-roxa moveu-se cerca de 535 km, com um deslocamento diária estimado de 8,92 km. A raia-roxa gastou apenas 9,8% do tempo em águas rasas entre 0- 50m de profundidade, com temperaturas entre 23,4 e 28,7°C. Em águas abaixo de 50m, passou 90,2% do tempo, desses, 70% foram em águas abaixo de 75m de profundidade, em temperaturas variando entre 13,0 e 24,5°C. Além disso, durante a maior parte do monitoramento (53%), o espécime ficou em águas entre 100- 150m de profundidade, com. A temperatura mínima experimentada pela raia-roxa foi de 10,4°C, correspondendo a 387,5 e 428,0m de profundidades, a última coincidindo com a atividade de mergulho mais marcante da raia-roxa. As diferenças entre o dia e a noite e preferências de profundidade pode indicar padrão de movimento circadiano, ou seja, migram diariamente, geralmente até águas rasas durante a noite e águas profundas durante o dia.

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23

Barlow, Paige Fithian. "Sea turtle bycatch by the U.S. Atlantic pelagic longline fishery: A simulation modeling analysis of estimation methods." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/34342.

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The U.S. pelagic longline fishery catches 98% of domestic swordfish landings but is also one of the three fisheries most affecting federally protected sea turtles (Crowder and Myers 2001, Witherington et al 2009). Bycatch by fisheries is considered the main anthropogenic threat to sea turtles (NRC 1990).

Accurate and precise bycatch estimates are imperative for sea turtle conservation and appropriate fishery management. However, estimation is complicated by only 8% observer coverage of fishing and data that are hierarchical in structure (i.e., multiple sets per trip), zero-heavy (i.e., bycatch is rare), and often overdispersed (i.e., larger variance than expected).

Therefore, I evaluated two predominant bycatch estimation methods, the delta-lognormal method and generalized linear models, and investigated improvements in uncertainty incorporation. I constructed a simulation model to evaluate bycatch estimation at two spatial scales under ten spatial models of sea turtle, fishing set, and observer distributions.

Results indicated that distributing observers relative to fishing effort and using the delta-lognormal-strata method was most appropriate. The delta-lognormal-strata 95% confidence interval (CI) was wider than statistically appropriate. The delta-lognormal-all sets pooled 95% CI was narrower but simulated bycatch was above the CI too frequently. Thus, I developed a bycatch estimate risk distribution to incorporate uncertainty in bycatch estimates. It gives managers access to the entire distribution of bycatch estimates and their choice of any risk level.

Results support the management agencyâ s observer distribution and estimation method but suggest a new procedure to incorporate uncertainty. This study is also informative for many similar datasets.
Master of Science

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24

Li, Yan. "Spatial dynamics modeling for data-poor species using examples of longline seabird bycatch and endangered white abalone." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/64003.

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Spatial analysis of species for which there is limited quantity of data, termed as the data-poor species, has been challenging due to limited information, especially lack of spatially explicit information. However, these species are frequently of high ecological, conservation and management interest. In this study, I used two empirical examples to demonstrate spatial analysis for two kinds of data-poor species. One example was seabird bycatch from the U.S. Atlantic pelagic longline fishery, which focused on rare events/species for which data are generally characterized by a high percentage of zero observations. The other example was endangered white abalone off the California coast, which focused on endangered species whose data are very limited. With the seabird bycatch example, I adopted a spatial filtering technique to incorporate spatial patterns and to improve model performance. The model modified with spatial filters showed superior performance over other candidate models. I also applied the geographically weighted approach to explore spatial nonstationarity in seabird bycatch, i.e., spatial variation in the parameters that describe relationships between biological processes and environmental factors. Estimates of parameters exhibited high spatial variation. With the white abalone example, I demonstrated the spatially explicit hierarchical demographic model and conducted a risk assessment to evaluate the efficacy of hypothetical restoration strategies. The model allowed for the Allee effect (i.e., density-dependent fertilization success) by using spatial explicit density estimates. Restoration efforts directed at larger-size individuals may be more effective in increasing population density than efforts focusing on juveniles. I also explored the spatial nonstationarity in white abalone catch data. I estimated the spatially explicit decline rate and linked the decline rate to environmental factors including water depth, distance to California coast, distance to land, sea surface temperature and chlorophyll concentration. The decline rate showed spatial variation. I did not detect any significant associations between decline rate and these five environmental factors. Through such a study, I am hoping to provide insights on applying or adapting existing methods to model spatial dynamics of data-poor species, and on utilizing information from such analyses to aid in their conservation and management.
Ph. D.

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25

Jaiteh, Vanessa. "An assessment of dolphin behaviour and bycatch mitigation techniques in the Pilbara Fish Trawl Fishery, Western Australia." Thesis, Jaiteh, Vanessa (2009) An assessment of dolphin behaviour and bycatch mitigation techniques in the Pilbara Fish Trawl Fishery, Western Australia. Honours thesis, Murdoch University, 2009. https://researchrepository.murdoch.edu.au/id/eprint/14594/.

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The incidental capture of unwanted species along with target species is a common and wasteful aspect of many fisheries. Trawl fisheries in particular have a high rate of incidental capture, or bycatch, due to the low selectivity of their nets. The bycatch of protected, endangered and threatened species is of particular concern and poses significant challenges for the ecologically sustainable management of wild capture fisheries. In the Pilbara Fish Trawl Interim Managed Fishery (PFTIMF), approximately 50 common bottlenose dolphins (Tursiops truncatus) are reportedly caught incidentally every year. Failure to adequately address the bycatch of this protected species has prevented the PFTIMF from attaining ‘Managed Fishery’ status. In this study, I analysed 195 hours of underwater video footage recorded inside active trawl nets in the PFTIMF to address the following aims: Chapter 2: a) examine and describe fine-scale dolphin behaviour in and around the trawl nets, and b) discuss the implications of these interactions for the reduction of dolphin bycatch in the fishery; and Chapter 3: a) assess the efficacy of two bycatch reduction devices (BRDs) at reducing the catch of dolphins and five other taxonomic groups of concern, and b) provide an estimate of the number of wildlife species caught annually in the PFTIMF. Dolphins frequently interacted with active trawl nets, and were recorded inside and outside the net for up to 98% and 99% of the trawl duration, respectively. Inside the net, dolphins exhibited a significantly higher proportion of foraging behaviours than outside the net, which may indicate that dolphins enter trawl nets because they provide a concentrated food source. Outside the net, dolphins most frequently engaged in ‘trampolining’, whereby they bounced on the upper surface of the net, often rubbing different body parts on the mesh. It thus appears that dolphins are motivated by several factors to approach and interact with active trawl nets. Most of the 29 individually identified dolphins returned to the net numerous times throughout a trawl, and seven individuals were re-sighted repeatedly in different trawls and on separate fishing trips. Entering trawl nets may thus be a specialisation exhibited only by a subset of the dolphin population in the region. Compared to the high interaction rates, bycatch events occur infrequently. This suggests that the majority of dolphin bycatch events in the fishery result from dysfunctional fishing gear, or when young or otherwise naïve dolphins enter the net. Results from the second part of this study indicate that the PFTIMF may capture in the order of 10,320 individuals of vulnerable wildlife species annually. Dolphins, large sharks and rays appear to be expelled most effectively (67%, 46% and 39% of all captured individuals respectively), but most sea snakes and pipefish are able to swim through the BRD grid’s bars into the codend. The high exclusion rate of dolphins suggests that the number of non-landed bycaught dolphins may be significant. The older grid model, which had a shallower decline and a centrally placed horizontal bar across the vertical bars, excluded a significantly larger proportion of wildlife bycatch than the newer grid model, which lacked a horizontal bar and was placed at a steeper angle. Some sea snakes, sharks, a dolphin and a turtle reacted to an interaction with the new grid by swimming upward, indicating that 1) a shallower decline guides animals toward the downward-opening escape hatch, and 2) BRDs should include an upward-opening escape hatch, for air-breathing animals in particular. Direct (post-capture) and indirect (post-release) fishing mortality is high in the PFTIMF; observer reports suggest that of all by catch landed during 44 analysed trawls, 77% were discarded dead. This stresses the need for improved BRD designs, particularly the introduction of upward-opening escape hatches and BRDs for smaller bycatch, such as sea snakes and pipefish. In order to establish the threat to stocks and populations resulting from incidental capture in the fishery, further investigation of the population size and the levels of removal of bycaught species is required. Continuous bycatch monitoring, particularly of dolphins and other vulnerable species, must be an important management objective of this fishery if it is to attain ‘Managed Fishery’ status.

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26

Hastey, John Pinkerton. "Effects of acute salinity and temperature change on Pacific hagfish, Eptatretus stoutii; implications for bycatch post release survival." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/37607.

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Hagfish captured as bycatch in a commercial fishery may be exposed to a range of elevated temperatures and reduced salinities when brought to the surface but it is not known how this will affect post-release survival. In this study, hagfish were exposed to all combinations of four salinities (33, 28, 23, and 18 g/l) and three temperatures (7, 16 and 25˚C) and sampled following 1, 3 or 6 h exposure to investigate sub-lethal affects on plasma osmolality, [Na⁺], [Cl⁻], [Mg²⁺], and glucose, hematocrit, mean cell haemoglobin concentration , muscle water content, as well as behavioural responses and survival. An additional group of hagfish were sampled after 48 h of recovery (33 g/l at 7˚C) following 3 h exposure to all salinity/temperature combinations to investigate latent effects of exposures. In general, during exposure to salinity and temperature combinations, plasma osmolality, [Na⁺] and [Cl⁻] decreased as: i) the salinity of exposure was reduced, ii) the duration of exposure was increased or iii) the temperature to which hagfish were exposed was increased. Plasma osmolality did not equilibrate with environmental osmolality within 6 h and appeared to approach an asymptote at 60% equilibration. Behavioural effects were observed during exposure to reduced salinity conditions at all temperatures and included full body contractions, reduced slime production, reduced swimming ability, extended body posture. During exposure to 25˚C, hagfish were often unresponsive to touch. Following 48 h of recovery from 3 h exposure to all salinity/temperature combinations most of the parameters measured were restored, with the exception of plasma glucose levels which remained elevated indicating latent stress. Following recovery from exposure to 23 and 18 g/l at 25˚C, morbidity levels of 14 and 100% were observed. Thus, hagfish captured and immediately brought to the surface and released, without exposure to extreme salinity or temperatures, may not physiologically be negatively affected by a catch and release fishery however, diminished survival should be expected if exposure salinity approaches 18 g/l or water temperature approaches 25˚C. Future research should address the implications of observed behaviours on release survival of hagfish in a natural setting.

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27

Wappelhorst, Annika. "In the Net : The Visual and Verbal Rhetoric of the Campaign “Operation Dolphin Bycatch” by Sea Shepherd France." Thesis, Jönköping University, HLK, Medie- och kommunikationsvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-54617.

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The marine conservation organization Sea Shepherd is most known for its radical direct action, e. g., against whale poaching. This thesis examines the campaign “Operation Dolphin Bycatch,” coordinated by the French branch of the NGO, through discourse analysis and interviews with Sea Shepherd France (SSF) members. Dolphins serve as the flagship species of the campaign. They allow SSF to criticize non-selective fishing methods that cause the accidental killing of dolphins in the Bay of Biscay. With expressions from war and religion, SSF portrays the French government and most fishermen as enemies of the dolphins’ wellbeing that pursue self-interested profit values. It is found that SSF positions itself as radical more in its worldview than its approaches. The ecological philosophy of biocentrism contradicts the anthropocentrism that dominates society. In this campaign, the NGO uses “outsider” tactics: It exerts pressure on French policy-makers with footage of dolphin bycatch and takes great care to maintain international legitimacy by staying within legal boundaries.
L’organisation de conservation du milieu marin Sea Shepherd est surtout connue pour ses méthodes d’action directe radicale, par exemple contre le braconnage des baleines. Ce mémoire de master examine la campagne « Opération Dolphin Bycatch », qui est coordonnée par la branche française de l’ONG, à travers une analyse multimodale du discours et des entretiens avec des bénévoles de Sea Shepherd France (SSF). Les dauphins sont l’espèce porte-drapeau de la campagne. Ils permettent ainsi à SSF de critiquer les méthodes de pêche non sélectives qui provoquent la mort accidentelle de dauphins dans le Golfe de Gascogne. Avec des expressions provenant des champs lexicaux de la guerre et de la religion, SSF dépeint le gouvernement français et la plupart des pêcheurs comme poursuivant des valeurs lucratives égoïstes à l’encontre du bien-être des dauphins. Il s’avère que SSF se positionne comme radicale dans sa vision du monde plus que dans ses approches. Sa philosophie biocentrée de l’environnement contredit l’anthropocentrisme qui domine la société. Dans cette campagne, l’ONG utilise des tactiques « extérieures », c’est-à-dire qu’elle exerce une pression sur les décideurs politiques français avec des images de prises accessoires de dauphins et prend soin de maintenir une légitimité internationale en restant dans un cadre légal.
Die Meeresschutzorganisation Sea Shepherd ist vor allem für ihre radikalen „Direct Action“-Methoden bekannt, beispielsweise gegen Wal-Wilderei. Diese Arbeit untersucht die Kampagne „Operation Dolphin Bycatch“, die vom französischen Zweig der NGO koordiniert wird, durch multimodale Diskursanalyse und Interviews mit Mitgliedern von Sea Shepherd Frankreich (SSF). Delfine dienen als Flaggschiff-Art der Kampagne. Sie ermöglichen es SSF, die nicht-selektiven Fischereimethoden zu kritisieren, die das versehentliche Töten von Delfinen im Golf von Biskaya verursachen. Mit Begriffen aus Krieg und Religion schreibt SSF der französischen Regierung und den meisten Fischerleuten eigennützige Profitinteressen zu und stellt sie als Feinde des Wohlergehens der Delfine dar. Es zeigt sich, dass SSF eher in ihrer Weltanschauung als in ihren Ansätzen eine radikale Position beansprucht. Ihre biozentrische Umwelt-Philosophie steht im Widerspruch zum Anthropozentrismus, der in der Gesellschaft vorherrscht. Bei dieser Kampagne bedient sich die NGO „Außenseiter“-Taktiken: Sie übt Druck auf französische Politiker*innen aus, indem sie Filmaufnahmen von Delfin-Beifang zeigt, und achtet durch das Einhalten gesetzlicher Vorgaben darauf, internationale Legitimität zu wahren.

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Reed, Jodie Romay. "Bycatch in the South African midwater trawl fishery for horse mackerel (Trachurus capensis) as established from observer records." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/19999.

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The South African midwater trawl fishery targets adult horse mackerel (Trachurus capensis) on the Agulhas Bank. The bulk of the catch is taken by a single midwater trawler. The bycatch of this fishery is investigated by analysing observer records from 2004 to 2014 to report on bycatch composition, volumes and temporal and spatial patterns. Small fauna were analysed by extrapolation of sample weights and large fauna were counted. The midwater trawl fishery was estimated to have caught 25 415 t annually, with a bycatch rate of 6.9% of the total catch, by weight. Bycatch species with the highest average annual catches were chub mackerel (Scomber japonicus), redeye roundherring (Etrumeus whiteheadi), ribbonfish (Lepidopus caudatus) and hake (Merluccius spp.). Large fauna bycatch species included Cape fur seals (Arctocephalus pusillus), sharks (15 species), sunfish (Mola mola) and cetaceans (two species). Temporal analysis revealed significant differences between day-time and night-time CPUE for nine species, and significant differences in seasonal CPUE for 17 species. Spatial analysis of small fauna species composition and of large fauna species composition identified three groups in each. The 100% observer coverage is high compared to other South African fisheries, and, although the average sampling rate of 1.56% is low, an increase in the sampling rate might not be feasible owing to the size of catches. The bycatch rate in this fishery is low compared to other South African trawl fisheries but similar to global midwater trawl bycatch rates. There are species overlaps with various fisheries, namely the demersal trawl, small pelagic, linefishery, shark longline and squid fisheries, yet the total catch estimates from this fishery are generally small relative to catches taken in the target fisheries.

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Rice, Wayne Stanley. "Contextualising the bycatch 'problem' in the Olifants Estuary Small-Scale Gillnet Fishery using an Ecosystem Approach to Fisheries." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/19987.

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Conventional fisheries management approaches have been shown, in many instances, to have been ineffective in dealing with complex conservation concerns such as bycatch. Greater considerations for broader-scale and holistic approaches, as proposed by the 'Ecosystem Approach to Fisheries' (EAF) and the 'balanced harvesting approach', are beginning to challenge some of the negative misconceptions around bycatch, especially in small-scale fisheries. The need for a more holistic approach to fisheries management, particularly in small-scale fisheries, in South Africa is highlighted by its commitment to an EAF and the recent Small-Scale Fisheries Policy, for which the Marine living Resource Act of 1998 provides the legal framework to implement. The case study of the Olifants estuary small-scale traditional gillnet fishing community, located on the west coast of South Africa, provides a particularly relevant example of a complex fishery requiring a holistic approach. Current regulations prohibit the harvesting or retention of any bycatch species. Fisheries management worldwide and in South Africa, generally view gillnet fisheries as destructive, due to the occurrence of bycatch and the fact that many of these bycatch species are considered overexploited, which has led to numerous attempts over the years to phase out the Olifants gillnet fishery. The purpose of this study was to, firstly, use an EAF framework to contextualise the issue of bycatch in the Olifants gillnet fishery, and secondly, to identify the relative contributions of all fisheriy sectors to the four key selected linefish species caught as bycatch by the fishery. An extensive review and analysis of available secondary data, as well as primary data collected for this study, have estimated, with acknowledged limitations, the magnitude of the exploitation by all known fisheries of these species. Key information from small-scale fisher interviews and community-monitoring data highlight the capture rate of key linefish species by this fishery. This is echoed by recent landings for 2012 indicating the relative contribution of the national beache seine and gillnet fishery to the overall catch of (Elf [Pomatomus saltatrix] - 26.94%; Silver Kob [Argyrosomus inodorus] - 0.88%; White Stumpnose [Rhabdosargus globiceps] - 1.05% - excluding the recreational sector). A significant finding of this study is the substantial levels of cross-sectorial exploitation of Silver Kob and White Stumpnose, and to a somewhat lesser extent Elf and White Steenbras.

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Thorpe, Teresa Mary. "The shark faunal assemblage of North Carolina, USA and assessment of a gillnet modification intended to reduce shark bycatch." Thesis, University of London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.536785.

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31

Metuzals, Kaija Irene. "Bycatch of harbour porpoise (Phocoena phocoena L.) in the North Sea : a case study of the Grimsby gillnet fleet." Thesis, University of Warwick, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247658.

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Björklund, Aksoy Simon. "Do potentially seal-safe pingers deter harbour porpoises (Phocoena phocoena) in the vicinity of gillnets and thereby reduce bycatch?" Thesis, Linköpings universitet, Biologi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-170512.

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Incidental bycatch in gillnets is a substantial threat to small cetaceans. Using Acoustic Deterrent Devices, “pingers”, have successfully reduced bycatch of harbour porpoises in gillnets. However, seals can use pingers as “dinner-bells” to easier find gillnets in order to raid and destroy them, further aggravating the existing conflicts between seals and coastal fisheries. Therefore, in the present study, the efficiency of two alleged “seal-safe” pingers, an experimental Banana pinger “SSB” and a Future Oceans F70 pinger “FO”, in deterring harbour porpoises from the vicinity of gillnets and thereby reducing bycatch in commercial gillnet fisheries, was tested. This was done by deploying click detectors, “C-PODs”, recording Detection Positive Minutes per hour, at each end of gillnets, provided with the two pinger types or no pingers at all. Bycatch instances were recorded into logbooks by participating fishermen and verified using video footage from on-board video cameras. Results showed that video monitoring was a reliable method for verifying the number of bycatches of porpoises and seals, but not seabirds, recorded in the fishermen’s logbooks. The experimental SSB pingers and the FO pingers significantly reduced porpoise presence, measured as Detection Positive Minutes per hour in the vicinity of the nets, compared to gillnets without pingers. However, the sample size was too small to yield a significant result regarding the bycatch reducing efficiency and dinner bell effect of the experimental pingers. Nevertheless, bycatch trends suggest that pingers did in fact reduce porpoise bycatch. Although both successful, FO pingers were slightly more efficient in deterring porpoises than SSB pingers. The SSB pinger sounds had bigger directionality variations than the FO pinger, which may have affected its deterrent effects. Therefore, additional trials are needed to further investigate this aspect.

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Silva, Thiago Elias da. "Dinâmica populacional de duas espécies de siris de importância econômica Achelous spinimanus (Latreille, 1819) e Arenaeus cribrarius (Lamarck, 1818) (Crustacea, Decapoda, Portunoidea) em uma área de proteção ambiental, no litoral sudeste brasileiro /." Botucatu, 2019. http://hdl.handle.net/11449/181870.

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Orientador: Adilson Fransozo
Resumo: Os siris Achelous spinimanus e Arenaeus cribrarius são capturados como fauna acompanhante da pesca camaroeira no litoral norte paulista. Ambas as espécies possuem valor comercial e por isso são aproveitadas e vendidas nas bancas de mercado. Estudar as característica da reprodução, distribuição e estrutura populacional dos recursos pesqueiros constitui uma ferramenta importante para elaboração de estratégias de manejo e conservação ambiental, visto que nem todas as espécies têm padrões similares em um mesmo local. Nesta tese foram analisadas as características reprodutivas (períodos de reprodução e recrutamento e tamanho de maturidade morfológica), distribuição ecológica e estrutura populacional de A. spinimanus e A. cribrarius no litoral norte paulista. Os animais foram coletados nas regiões de Ubatuba e Caraguatatuba, litoral norte do estado de São Paulo, Brasil. Foi verificado que A. spinimanus e A. cribrarius possuem períodos reprodutivos em estações do ano diferentes, no inverno e verão, respectivamente. Também foi possível observar que A. spinimanus tem pico de recrutamento após o pico de A. cribrarius. Estas diferenças temporais das características reprodutivas podem representar uma estratégia evolutiva para evitar competição por alimento com outras espécies. Comparando as estimativas de tamanho de maturidade sexual com outros estudos, também foi possível observar certa plasticidade reprodutiva para ambas as espécies, o que sugere que esta característica pode variar tem... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The swimmong crabs Achelous spinimanus and Arenaeus cribrarius are caught as bycatch of the shrimp fishery on the north coast of São Paulo. Both species have commercial value and are therefore used and sold in the market stalls. Studying the characteristics of the reproduction, distribution and population structure of the fishery resources constitutes an important tool for the elaboration of strategies of management and environmental conservation, since not all the species have similar standards in the same place. In this thesis the reproductive characteristics (breeding and recruitment periods and size of morphological maturity), ecological distribution and population structure of A. spinimanus and A. cribrarius in the north coast of. The animals were collected in the regions of Ubatuba and Caraguatatuba, north coast of the state of São Paulo, Brazil. It was verified that A. spinimanus and A. cribrarius have reproductive periods in different seasons of the year, in winter and summer, respectively. It was also possible to observe that A. spinimanus has peak recruitment after the peak of A. cribrarius. These temporal differences in reproductive characteristics may represent an evolutionary strategy to avoid competition for food with other species. Comparing estimates of sexual maturity size with other studies, it was also possible to observe a certain reproductive plasticity for both species, suggesting that this characteristic can vary temporally and spatially. A. spinimanus ... (Complete abstract click electronic access below)
Doutor

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Montrond, Gilson. "Assessing sea turtle, seabird and shark bycatch in artisanal, semi-industrial and industrial of fisheries in the Cabo Verde Archipelago." Master's thesis, Faculty of Science, 2021. http://hdl.handle.net/11427/32854.

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Firstly, I am very grateful to Birdlife International for the MSc scholarship. I am also very grateful to Professor Peter Ryan of the FitzPatrick Institute of African Ornithology, University of Cape Town, for agreeing to supervise this project and for his guidance, insights and comments on the write-up. I am grateful to Sarah Saldanha, for all the support during this MSc. Many thanks also to Dr Ross Wanless, Dr Rima Jabado and Ruben Rocha for all support, guidance and advice. I want to thank a lot Andy Angel for their accommodation and all support in South Africa. I am grateful to all the UCT staff and BirdLife Senegal Staff for all the support during this study. Many thanks to my family for all the encouragement and support. I want to thank to all the Cabo Verde fishers for their willingness to share their knowledge and experience. Finally, many thanks to the Conservation Biology class of 2019, for all their support.

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Gahm, Meghan P. "The development and evaluation of small specialized turtle excluder devices to reduce sea turtle bycatch in various small shrimp gears." ScholarWorks@UNO, 2019. https://scholarworks.uno.edu/td/2665.

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In the southeastern United States, skimmer trawls, pusher-head trawls, wing nets, and small try nets (headrope length less than 12-ft (3.66-m)) are exempt from using a turtle excluder device (TED) and instead must adhere to tow time restrictions as a mode to mitigate sea turtle bycatch. However, observer and stranding data indicate that these tow times may often be exceeded and result in mortality of sea turtles. The National Marine Fisheries Service (NMFS) published a notice of proposed rulemaking in December 2016 to extend TED requirements to other trawl types, however there has been limited development of specialized TEDs for these smaller trawls. In anticipation of a regulatory change, we developed and identified multiple versions of a top-opening TED with a minimum width of 28-in (71-cm) and height of 24-in (61-cm) as the best option for small trawl gears. Prototypes were initially equipped within small try nets and tested for gear performance and sea turtle exclusion in Panama City, Florida. The final designs were then tested for target shrimp retention, bycatch reduction, and general usability of TEDs in the commercial fisheries. A paired comparison test was conducted in 8-ft (2.44-m) and 10-ft (3.05-m) try nets aboard the NMFS R/V Caretta, three commercial skimmer trawls in vesselsFarfantepenaeus duorarum) fishery. There was a general reduction of shrimp and bycatch averaging from a minimum loss of 3.31% in the Miami wing net fishery (FV FL-01) to 22.07% in the skimmer trawl fishery (FV LA-01). This dissertation research indicates that TEDs can function properly in small trawl types, however additional studies are recommended to minimize the shrimp loss and improve the overall TED effectiveness specific to each fishery and trawl type evaluated.

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Foster, Sarah Jane. "Is bycatch a big problem for small fish? Assessing and addressing the impacts of tropical shrimp trawling on small fish species." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/17458.

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My research, focused on the industrial shrimp fishery in southern Gulf of California, aimed to determine whether tropical shrimp trawling is a problem for viability of incidentally captured small fish species. My first objective was to use life history information to evaluate possible impacts on four small fish species from their incidental capture. I applied length based indicators and qualitative criteria to information on captured sizes, reproduction, and distributions across the study site. My results suggested potential for overfishing silver stardrum and bigscale goatfish, largely because most sampled individuals were immature. Silver stardrum may be particularly affected because its occurrence and density declined during the trawling season whereas goatfish apparently recruited to the study area. Most sampled sandperch were mature, suggesting greater resilience to trawling. In contrast, sampled lumptail searobin, although mature, had not yet spawned, indicating potential for adverse fishing effects. Because human behaviour affects the success of fisheries management, my second objective was to shed light on the social dimensions of tropical shrimp fisheries management. My interviews with industrial trawl fishers suggested that proper enforcement and reliable governance are essential for a sustainable fishery. If enforcement were strong, then most fishers would support trawl free areas. The effort data I gathered point to areas where protection might be socially acceptable. My third objective considered the biological appropriateness of trawl closures for small fishes. The divergent distributions of bigscale goatfish and silver stardrum, just two of many small species in bycatch, implied that trawl restrictions would have to cover many depths and latitudes. Further, although my matrix model was of limited use for assessing population status of silver stardrum, it clearly indicated that precautionary management should focus on increasing survival of younger fish. This could be achieved with trawl closures where smaller fish live. While the approaches I used identified small fishes that might be vulnerable to trawling, they are too data intensive to be viable for the hundreds of such species in bycatch, and too inconclusive to confirm impact. It may be necessary to apply precautionary methods such as trawl closures to avoid potential effects of indiscriminate trawling.

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Mangel, Jeffrey Charles. "Interactions of Peruvian small scale fisheries with threatened marine vertebrate species." Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/3483.

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Marine vertebrate species face unprecedented and ever increasing pressures as a result of human activity, primarily fishing, in the global oceans. One area of growing concern has been for the impacts of small-scale fisheries on these species. Over the past decade it has become increasingly clear that these under-studied fisheries have sizeable levels of catch and bycatch of many threatened and endangered species of sea turtles, seabirds and small cetaceans. This thesis presents a collection of chapters that investigate aspects related to the interactions of small-scale fisheries with threatened marine vertebrates. We identify sizeable rates of bycatch of small cetaceans and seabirds for multiple small-scale longline and gillnet fisheries in both Peru and Ecuador. Catch rates of small cetaceans by the Peruvian small-scale driftnet fleet are estimated to exceed 10,000 dolphins and porpoises annually. A trial of acoustic alarms (pingers) in this same fishery showed a 37% reduction in small cetacean bycatch while not reducing target catch and represents a promising bycatch mitigation measure. Seabird bycatch was also found to be high in both longline and gillnet fisheries and included a wide range of seabird species including the critically endangered waved albatross (Phoebastria irrorata). Through post-capture satellite tracking of loggerhead turtles (Caretta caretta) we show that these turtles are present in pelagic waters off the coasts of Peru and Chile for extended periods during which they are at risk of repeat interactions with small-scale longline fisheries operating throughout their foraging habitat. Through scan and focal sampling of the endangered marine otter (Lontra felina) we also show that otters making den sites in human fishing communities face additional risks due to entanglement in fishing gear or interactions with feral animals but, if properly managed, these sites could serve as stepping stones for marine otters along the coast. The results presented here, gathered using a wide range of techniques, including onboard observer and shore-based monitoring, satellite tracking, bycatch quantification, and bycatch mitigation experiments, represent an attempt to better characterize and quantify the interactions of small-scale fisheries with threatened marine vertebrates toward identifying solutions that can lead to sustainable fisheries and populations of these protected marine species.

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Jakobsson, Ellinor. "Status för den vanliga tumlaren (Phocoena phocoena) : En analys av tumlarens rödlistning och hot samt av betalningsviljan för att bevara tumlare." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-150251.

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The aim of this report was to establish what category the harbour porpoise is listed as on the Swedish national redlist as well as analyze what potential sub-criteria the species fulfills besides criteria already established. The aim was also to evaluate the willingness to pay for conservation of the harbour porpoise for the first time and make a comparison of the willingness to pay between geographic places where the harbour porpoise is currently existing and where it is not. The subpopulation of the harbour porpoise in Skagerrak-Kattegat is listed as vulnerable (VU) on the national redlist and the subpopulation in the Baltic sea is listed as critically endangered (CR). Actions and precautions which have been made for conservation and protection of the harbour porpoises in Swedish waters are new Swedish laws and law proposals as well as formations of organizations such as ASCOBANS and further research. The results from the survey showed that the mean of the single time payment sum those questioned were prepared to pay to retain the porpoises at a stable population level was 273 SEK. Geographically the study showed no significant difference in geographic position and where the harbour porpoise exists but showed that the inhabitants of the south-east coast were willing to pay about half the sum, 165 SEK, of the mean sum that the north-east coast were willing to pay, 335 SEK. The results regarding the populations’ conjecture of historical threats and threats nowadays showed a significant difference from reality. Overfishing of prey had the highest amount of answers as a threat both historically and nowadays. Bycatch, which is accepted as todays biggest threat by researchers and organizations, came third place in the results from the survey study with a percentage of 14.5 %.

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Lange, Louise. "Use of demersal bycatch data to determine the distribution of soft-bottom assemblages off the West and South coasts of South Africa." Doctoral thesis, University of Cape Town, 2012. http://hdl.handle.net/11427/10899.

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Includes abstract.
Includes bibliographical references.
This project aims to analyse information on invertebrate biodiversity patterns of the offshore benthos around South Africa. Samples were collected as bycatch from demersal trawl surveys conducted along the South (one cruise) and West Coasts (two cruises).

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Snouck-Hurgronje, Julia. "The Effects of Drifting Fish Aggregating Devices on Bycatch in the Tropical Tuna Purse Seine Fisheries in the Atlantic and Indian Oceans." W&M ScholarWorks, 2016. https://scholarworks.wm.edu/etd/1499449678.

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Thousands of floating objects, known as drifting fish aggregating devices (dFADs), are released every year by commercial tropical tuna purse seine vessels in the three equatorial oceans to aggregate tuna and increase catch. The escalation in the number of dFADs deployed over the last three decades has caused changes in fishing effort that are poorly reflected in traditional indices of purse seine effort and catch per unit of effort (CPUE). In addition, concerns have been raised regarding the impacts of such high numbers of dFADs being deployed on both catch and bycatch species. I studied two aspects of dFAD deployments in order to clarify how dFADs are used by purse seiners and how they affect the magnitude of bycatch. My specific goals were to determine how often purse seine vessels fish on the dFADs they deploy and how regional dFAD density affects the magnitude of bycatch and catch. I analyzed commercial data, independent observer data, satellite buoy trajectories, and estimated floating object densities from the French tropical tuna purse seine fisheries in the Atlantic and Indian Oceans to examine these relationships. My results indicate that only 2.7-20.6% of dFAD fishing sets were on the dFADs that French purse seiners deployed over the period 2007-2013. Although this percentage increased over time, such a low percentage suggests that French vessels do not primarily increase CPUE by using the dFADs they deploy for directed fishing. If French purse seiners are not mainly using their own dFADs in this manner, then using a metric of nominal effort based on individual vessel activity is unlikely to produce reliable CPUE estimates for the fishery. While information about how often purse seiners fish on their own dFADs could be incorporated into indices of fishing effort, it may be just as important, if not more so, to quantify the collective component of dFAD releases for overall fishing effort. The results for the second objective showed that average dFAD density had a relatively weak relationship with total bycatch biomass. There was no statistically significant effect on mean total bycatch biomass, but dFAD density was related to heteroscedasticity in bycatch biomass. In particular, there was a significant negative relationship between dFAD density and the upper quantiles of the bycatch biomass distribution, suggesting that dFAD density determines the upper bound for bycatch biomass caught per set. These relationships were not constant across species, however, as the five most prevalent bycatch species (i.e., those caught in the greatest number of sets) showed a mix of positive, negative, or no relationships to dFAD density. The total biomass of catch increased significantly as average dFAD density increased both at the mean and throughout the majority of the distribution, although this effect only explained a small fraction of the total variance in catch biomass. at this time, the low amount of variance explained and the inconsistent impact of average dFAD density on bycatch and target species indicate that it would be ineffective to mitigate bycatch levels in these fisheries by attempting to control regional dFAD densities.

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Jenkins, David M. "Using Long-term Mark-recapture Data to Quantitatively Assess Conservation Strategies for the Diamondback Terrapin, Malaclemys terrapin." Ohio University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1534246552720847.

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Neves, Pedro Manuel Cancela das. "Estimating captures and discards of the beach seine conducted in Mira (Coimbra)." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17464.

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Mestrado em Biologia Marinha
Fishing is a vital source of nutrients for human consumption, and Portugal yields one of the highest fish consumption per capita in Europe (61.77 kg per capita in 2007). Being recognized as a worldwide important activity, fisheries have induced serious depletions in natural fish populations due to overexploitation and lack of adequate management. Another issue related with fisheries are the IUU (Illegal, Unreported and Unregulated) captures, which represents a portion of what is extracted from the ocean that it is not known. This includes unreported bycatch and, consequentely, discarded specimens. The knowledge of discards is crucial for more adequate management. Beach seine is an artisanal fishery conducted in the Portuguese coast. Little information is available regarding its activity. Due to its practice, the impacts on the ecosystem needs proper assessment, especially due to large amount of discards that it generates. To address this issue, the present work aims to analyse captures and discards from beach seine fisheries occurring at Praia de Mira (Coimbra, Portugal) during the summer season of 2016 (June-September, week numbers 22 to 36 – W22 to W36) of four crews. Captures data were provided by Docapesca, while discards data (obtained upon analysis of thirteen samples) were only collected from one vessel. Data on captures of 2015 were also studied to assess yearly variations. Differences in Landings Per Unit Effort (LPUE) of the four crews were detected between both years. Results also shows that 99.53 tons (23 taxa) of marine resources (including fish, squids and crustaceans) were landed and auctioned during the study period of 2016 (W22-W36), which was a lower amount when comparing landings from 2015 (219.00 tons, 24 taxa, within the same period). Trachurus trachurus (Linnaeus, 1758) was the most auctioned species in both years (127 tons in 2015 and 69 tons in 2016), also representing the species where fishermen got their most profits. After proper data adjustment, an average 50 kg of marine resources per haul were discarded, representing typically 15-60% of the total captured. The anchovy Engraulis encrasicolus (Linnaeus, 1758) was found to be the most common discarded species, making up to a total of 1.9 tons. Other abundant discards included T. trachurus, Sardina pilchardus (Walbaum, 1792), Trisopterus luscus (Linnaeus, 1758) and the Henslow’s crab Polybius henslowii Leach, 1820. These last three species had an estimated 100% discard rate per haul, while T. trachurus was usually below 3%, except in four hauls. Possible reasons for yearly differences to occur and motives for discarding were discussed. The low contribution of this fishery on the national scenario (estimated 0.46% of multi-gear captures) does not reflect its importance to the local community. Further decrease on operating beach seine crews on a national scenario is expected. To prevent this occurrence, proper assessments should be performed in order to increase its sustainability.
Os recursos pesqueiros são uma fonte vital de nutrientes, e Portugal apresenta um dos maiores consumos de peixe da Europa (61.77 kg de peixe per capita em 2007). Sendo reconhecida como uma atividade importante a nível mundial, a pesca induziu graves depleções de stocks pesqueiros devido à sobrepesca e à falta de gestão adequada. Outra questão relacionada com as pescarias são as capturas ilegais, não reportadas e não regulamentadas, representando uma fração que é extraída do oceano e não é conhecida. Esta fração inclui as capturas acessórias e, consequentemente, os espécimes rejeitados que não são reportados. O conhecimento das rejeições é crucial para avaliações mais precisas dos stocks, bem como para medidas de otimização do uso e comercialização do pescado. A Arte Xávega é um tipo de pesca artesanal que é conduzida na costa Portuguesa. Existe pouca informação disponível relativamente à sua atividade. Devido à sua prática, os impactos da sua atividade no ecossistema necessitam de uma avaliação adequada, especialmente ao nível da quantidade de rejeições produzidas. Para analisar esta questão, este trabalho tem como objetivo as capturas e rejeições produzidas pela Arte Xávega que decorre na Praia de Mira (Coimbra, Portugal) durante o Verão de 2016 (Junho-Setembro, semanas 22 a 36 – W22 a W36) de quatro companhas. Dados das capturas foram fornecidos pela Docapesca, enquanto os dados relativos às rejeições (obtidos através da análise de treze lances) foram apenas recolhidos para uma companha. Dados relativos às capturas de 2015 foram também estudadas com o objetivo de avaliar as diferenças anuais. Diferenças nas Desembarques Por Unidade de Esforço (DPUE) das quatro companhas entre os dois anos foram detetadas. Resultados também indicam que 99.53 toneladas (23 taxa) de recursos marinhos (incluindo peixes, lulas e crustáceos) foram desembarcados e leiloados durante o período estudado de 2016 (W22-W36), o que representa um decréscimo quando comparado com os dados de 2015 (219.00 toneladas, 24 taxa, no mesmo período). Trachurus trachurus (Linnaeus, 1758) foi a espécie mais leiloada nos dois anos (127 toneladas em 2015 e 69 toneladas em 2016), representando também a espécie onde os pescadores obtiveram maiores rendimentos. Após ajustamento dos dados, uma média de 50 kg de recursos marinhos por lance foram rejeitados, representando tipicamente 15-60% do total capturado. A anchova Engraulis encrasicolus (Linnaeus, 1758) foi a espécie mais rejeitados, sumarizando um total de 1.9 toneladas. Outras espécies rejeitadas abundantes incluem o T. trachurus, Sardina pilchardus (Walbaum, 1792), Trisopterus luscus (Linnaeus, 1758) e o caranguejo-pilado Polybius Henslowii Leach, 1820. Estas últimas três espécies tiveram uma taxa de rejeição por lance estimada de 100%, enquanto a taxa do T. trachurus encontrava-se usualmente abaixo dos 3%, exceto em quatro lances. Possíveis razões para a ocorrência das diferenças anuais e motivos para a rejeição foram discutidos. A baixa contribuição desta pescaria no cenário nacional (estimada em 0.46% da pesca polivalente) não reflete a importância desta na comunidade local. Um decréscimo do número de companhas a exercer esta atividade é esperado. Para prever esta ocorrência, estudos deverão ser feitos com o objetivo de aumentar a sua sustentabilidade.

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Burns, Karen Mary. "Evaluation of the Efficacy of the Minimum Size Rule in the Red Grouper and Red Snapper Fisheries With Respect to J and Circle Hook Mortality and Barotrauma and the Consequences for Survival and Movement." [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0002928.

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Burns, Anthony G. "A Comparison of Circle and J Hook Performance within the Grenadian Pelagic Longline Fishery." Thesis, NSUWorks, 2019. https://nsuworks.nova.edu/occ_stuetd/510.

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The development and adaptation of gear technologies to local fisheries has been a management-oriented research strategy commonly used to mitigate the ecological effects of pelagic longline (PLL) gear on bycatch species. Grenada’s PLL fishery primarily targets yellowfin tuna, however while minimal, their bycatch of blue marlin and white marlin exceeds the Total Allowable Catch (TAC) allowed by the International Commission for the Conservation of Atlantic Tunas (ICCAT). A switch to circle hooks may benefit these nontargeted, bycatch species by reducing catch rates and haulback mortality, as well as increasing post-release survival. To determine differences in performance, assessments of 16/0 circle hooks and 9/0 J hooks were alternated over 26 sets between January and June 2018. Catch, mortality, hook location, length and grade of fish were compared between hook types. No differences in haulback mortality rate for all species, or yellowfin tuna grade were found between hook types. However, significantly fewer billfish collectively (t= 2.36, p= 0.028), and sailfish specifically (t= 3.04, p=0.005), were caught on circle hooks. Additionally, tuna caught with circle hooks had a 69% greater chance of external hooking compared to J hooks (X2 = 4.38 p=0.036). All other species analyzed had statistically similar catch rates regardless of hook type (p < 0.05), including, yellowfin tuna. The results of this study indicate the Grenadian PLL can reduce its impact on billfish bycatch by using 16/0 circle hooks without incurring negative effects on their tuna catch rate or grade. This research provides further evidence that circle hooks should be the recommended gear type when using a bycatch mitigation approach to manage PLL fisheries.

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Bayse, Shannon Michael. "Comparing Catches and Catch Rates by Variable Strength Hooks from Pelagic Longlines to Determine Their Bycatch Reduction Potential for Pilot Whales in the MidAtlantic Bight." NSUWorks, 2009. http://nsuworks.nova.edu/occ_stuetd/237.

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The pelagic longline fishery in the western Atlantic Ocean targeting swordfish (Xiphias gladius) and tunas (Thunnus spp.) historically has a high frequency of interactions with marine mammals, particularly pilot whales (Globicephala spp.) in the Mid-Atlantic Bight (MAB) region. Typical pelagic longline hooks used in the MAB are size 16/0 "strong" hooks that straighten at 250 lb of pull (113 kg), while alternative "weak" hooks straighten at 150 lb of pull (68 kg). Taking advantage of the size difference between large bycatch and relatively smaller target species, these "weak" hooks could be implemented as a bycatch reduction agent. To test this within the tuna fishery of the MAB, 21 sets were made using size 16/0 hooks, targeting yellow fin tuna (Thunnus albacares) and bigeye tuna (T. obesus) alternating strong and weak hooks. To test these hooks in a swordfish targeted area, nine sets were made using larger size 18/0 hooks within the Florida East Coast statistical area (FEC) and the Charleston Bump of the Southern Atlantic Bight statistical area (SAB) alternating strong and weak hooks. Size 18/0 strong hooks straighten at 350 lb (159 kg) of pull, while the weak straightens at 225 lb (102 kg). Results for the tuna targeted sets showed no significant reduction in total catch (a < 0.05) of any target species, with weak hooks having higher trends for catch per unit effort (CPUE) for both tuna and swordfish. The only species to show a significant difference in total catch between strong and weak 16/0 hooks was the pelagic stingray (Pterplatytrygon violacea), with more individuals caught by the strong hook. The 18/0 hook sets had similar catches for all species except the target species swordfish. Swordfish CPUE trended higher for the strong hook, while also having significantly higher total catches. Seven weak hooks were retrieved straightened at haul back; one of these hooks was observed being straightened by a pilot whale at 10m distance from the vessel.

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Quadrone, Liborio Enrico. "Identificazione, descrizione e analisi ecologica della parassitofauna gastrointestinale di Elasmobranchi del Mar Mediterraneo." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.

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Questo studio mira a identificare a livello morfologico e molecolare i parassiti elminti ritrovati nello stomaco e nell’intestino di diversi elasmobranchi rinvenuti dalle catture accessorie della pesca nel ma Mediterraneo con lo scopo di aggiornare e fornire nuove informazioni sulla fauna parassitaria di queste specie. Inoltre, basandoci sui resti alimentari ritrovati negli elasmobranchi analizzati, abbiamo cercato di ricostruire ove possibile le relazioni tra ospite e parassita lungo la catena trofica. Sono stati esaminati 6 palombi comuni Mustelus mustelus, 8 palombi puntati Mustelus punctulatus, 1 verdesca Prionace glauca, 1 gattuccio Scyliorhinus canicula, 9 trigoni Pteroplatytrygon violacea e 29 razze stellate Raja asterias. Lo studio parassitologico condotto sulle due specie Mustelus mustelus e Mustelus punctulatus, ha permesso di identificare morfologicamente e mediante analisi molecolari un’unica specie di nematode: Acanthocheilus rotundatus. In Prionace glauca sono state identificate 3 specie di cestodi: Scyphophyllidium exiguum, Anthobothrium caseyi e Nybelinia indica, mentre l’analisi parassitologica eseguita su Raja asterias ha permesso di identificare 3 esemplari di nematodi del genere Pseudanisakis e una specie di cestode del genere Nybelinia. Tra questi elminti, alcuni rappresentano nuove segnalazioni a livello geografico, in particolare Anthobothrium caseyi in Prionace glauca nel Mar Mediterraneo, o di ospite, come ad esempio Scyphophyllidium exiguum e Nybelinia indica in Prionace glauca o Pseudanisakis sp. in Raja asterias. I risultati di questa indagine rappresentano un contributo per ampliare le conoscenze della parassitofauna di questi elasmobranchi nel Mar Mediterraneo. Da studi futuri più approfonditi si potranno raggiungere evidenze e conclusioni generali più solide su aspetti relativi alla biologia, ecologia e allo stato di salute di queste specie, offrendo utili informazioni per una loro corretta conservazione e gestione.

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Guimarães, Fernanda Jordão. "Biologia do Camarão-Sete-Barbas, Xiphopenaeus kroyeri (Heller,1862)(Crustacea, Decapoda, Penaeidae) e aspectos da sua pesca na reserva extrativista Marinha do Corumbau, BA." Universidade Federal da Paraíba, 2009. http://tede.biblioteca.ufpb.br:8080/handle/tede/4100.

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Made available in DSpace on 2015-04-17T14:55:16Z (GMT). No. of bitstreams: 1 parte1.pdf: 2329943 bytes, checksum: 1cc93d9438f7097161f07a019201fb74 (MD5) Previous issue date: 2009-09-30
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The Corumbau marine extractive reserve (MER) was the first MER specifically designed to protect coral reefs. Fishers and their families were directly dependent on extractive activities in the area. The objective of this research, was to study the biology of the sea bob shrimp Xiphopenaeus kroyeri (Heller, 1862), its fisheries aspects and evaluate the effectiveness of a bycatch reduce devices (BRD). Fish landings were daily monitored between Aug/04 and Dec/06. Shrimp samples landed (Jul/04 to Jan/07) were weekly analyzed. Monitored fisheries, in the ten main fishing grounds around the region (Jan/07 to Jan/09), were seasonally carried out. The BRD was tested (Feb/06 and Aug/06) in an experimental net, with a conded composed of a standard net (30mm mesh) and a squaremesh (50mm) front top panel (50x50cm) and compared with a net control. A total of 55.409 individuals were sampled. The CL50 found was 12.55 mm. Females reach larger sizes (CL = 38.59 mm), a higher longevity (tmax = 26 months) and had lower growth rate (kmonth = 0.17) than males (CL = 32.35 mm; tmax = 16 months and kmonth = 0.28). The sex ratio did not differ between females and males, suggesting that trawl fisheries in Corumbau MER act mainly in growth and mating areas, not in spawning locations. There was a higher female frequency in reproductive activity in the first semester, mainly related to a higher transparency, salinity and water temperature. Rare events of Tropical Water mass probably led to favorable spawning conditions, even in places near to the coast. Recruitment period was continuous with the main peak occurring in July/August. The highest juvenile abundance was associated with higher water turbidity and pH values. Trawl fishery in Corumbau MER is handmade, not going over an isobaths average of 15m. The departures are daily held, mainly focused in the morning, minimizing the need for fish cooling and reducing the operations cost. Fishing effort varied among the communities, being greatest in Corumbau, followed by Cumuruxatiba and then Caraíva. The fishing grounds use varied seasonally, often related to climatic conditions and water visibility. X. kroyeri was the most abundant penaeid (96.4%) in all communities landings, with high fishing performance in Corumbau. The higest X. kroyeri CPUEs occurred during the autumn and winter, showing a negative correlation with water visibility and temperatures, coinciding with species recruitment. Around 50% of the fisheries act on less than 15mm CL individuals size. Thus, fishing in that region, may be running in an inappropriate way to sustainable resource management. The white shrimp (L. schmitti) production was very low compared to other species, although it was present all year round, in the three communities. The pink shrimp (F. brasiliensis and F. paulensis) production was higher in Cumuruxatiba, where a clear seasonal pattern is observed. A low CPUE was registered during winter and gradually increasing over the years, with harvest peak occurring in fall. Shrimp captures were probably limited to species recruitment period. During the experiment for bycatch reduce us identified 93 fish taxa, 89 belonging to Actinopterygii Class and 3 to Chondrichthyes Class. The square mesh nets are effective in excluding bycatch without affecting the catch of sea bob shrimp. The behavior, body shape and swimming ability were crucial for fish escape success from the panel, favoring especially the larger ones. A difference in fish assemblage could be established between sampling periods, not changing the device efficiency. Besides, depth regardless, a positive effect of square mesh panel was observed. Thus, this device use is very promising tool due to its structural features, as well as having low cost, been easy to purchase and to install.
A RESEX Corumbau é uma Unidade de Conservação de uso direto, que abriga uma porção representativa do Banco dos Abrolhos, sendo que a maior parte dos extrativistas dedica-se à pesca. O objetivo deste trabalho foi estudar a biologia do camarão Xiphopenaeus kroyeri (Heller, 1862), os aspectos da sua pesca e testar a eficiência de um dispositivo de redução de captura da fauna acompanhante. Os desembarques pesqueiros foram monitorados diariamente entre ago/04 e dez/06. Amostras dos camarões desembarcados (jul/04 a jan/07) foram analisadas semanalmente. Arrastos monitorados nos dez principais pesqueiros da região (jan/07 a jan/09) foram realizados sazonalmente. O dispositivo de redução foi testado (fev/06 e ago/06) em uma rede experimental, com o ensacador de malha 30mm e com um painel (50x50cm) localizado na parte anterior superior, confeccionado com malha quadrada (50mm) e comparados com uma rede controle. O total de 55.409 indivíduos foi amostrado. O CC50 encontrado foi de 12,55mm. As fêmeas atingem tamanhos maiores (CC=38,59mm), uma longevidade mais alta (tmax=26 meses) e apresentam índice de crescimento menor (kmês=0,17) que os machos (CC=32,35mm; tmax=16 meses e kmês=0,28). A razão sexual não diferiu, sugerindo que as pescarias de arrastos na RESEX Corumbau atuam principalmente em áreas de crescimento e acasalamento e não de desova. Verificou-se uma maior freqüência de fêmeas em atividade reprodutiva no primeiro semestre, relacionada principalmente com uma maior transparência, salinidade e temperatura da água. Eventos raros de entrada da massa de Água Tropical provavelmente propiciaram condições favoráveis à desova, mesmo em locais próximos a costa. O período de recrutamento foi contínuo, com o pico principal ocorrendo em julho/agosto. A maior abundância de jovens ocorreu associada a maiores valores de turbidez e pH da água. A pesca de arrasto na RESEX Corumbau é artesanal, não ultrapassando a isóbata média de 15m. As saídas são realizadas diariamente, concentrando-se principalmente pela manhã, minimizando a necessidade de resfriamento do pescado e diminuindo o custo das operações. O esforço de pesca variou entre as comunidades, sendo maior em Corumbau seguido por Cumuruxatiba e depois Caraíva. A utilização dos pesqueiros variou sazonalmente, sendo freqüentemente relacionada com as condições climáticas e com a visibilidade da água. X. kroyeri foi o peneídeo mais abundante (96,4%) nos desembarques de todas as comunidades, com o rendimento pesqueiro médio mais elevado em Corumbau. As maiores CPUEs de X. kroyeri ocorreram no durante o outono e o inverno, e apresentando uma relação negativa com a visibilidade e a temperatura da água e coincidindo com o período de recrutamento da espécie. Cerca de 50% das pescarias atuam sobre indivíduos com tamanho inferior à 15mm de CC. Assim, a pesca na região pode estar sendo executada de maneira inadequada ao manejo sustentável deste recurso. A produção do camarão VG (L. schmitti) foi muito baixa em relação às outras espécies, embora o mesmo esteja presente em todas as estações do ano, nas três comunidades. A produção de camarão rosa (F. brasiliensis e F. paulensis) foi maior em Cumuruxatiba, onde se pode observar uma nítida variação sazonal, com a CPUE baixa durante o inverno e aumentando gradativamente ao longo do ano, com o pico da safra ocorrendo no outono. As capturas do camarão rosa, provavelmente, foram limitadas ao período de recrutamento da espécie. Durante o experimento de redução de fauna acompanhante foram identificadas 93 espécies de peixes, sendo 89 pertencentes a Classe Actinopterygii e 3 a Classe Chondrichthyes. Foi possível verificar que as redes com o painel de malha quadrada são eficientes na exclusão da ictiofauna acompanhante, sem alterar as capturas de camarões sete-barbas. O comportamento, o formato do corpo e a capacidade de natação influenciaram a capacidade dos peixes para escaparem pelo painel, favorecendo, principalmente, os indivíduos de maior porte. Foi possível identificar diferenças nas assembléias de peixes entre os dois períodos analisados, sem alterações na eficiência do dispositivo. Além disso, independente da profundidade, o efeito positivo do painel de malha quadrada foi observado. Desta forma, a utilização desse dispositivo é bastante promissora devido à suas características estruturais, além de possuir baixo custo e ser de fácil aquisição e instalação.

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Miller, Nathan. "The Gulf of Mexico Red Snapper Individual Fishing Quota Program: The Effects on the Fishing Industry and Potential Outlook." Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3626.

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In January 2007, the Gulf of Mexico red snapper fishery took a step toward sustainability and began management under an individual fishing quota (IFQ) system. The hope is that direct ownership stakes by fishers brings more direct involvement on behalf of the boat owners and fishermen as well as more responsible and sustainable fishing practices on depressed fish populations. The research was conducted in order to study the welfare of local fishing communities as well as the effects on the red snapper fishery itself. Traditional fisheries and economic data were analyzed. In addition a Data Envelopment Analysis (DEA) of the Florida Gulf Coast communities involved in the red snapper fishery was performed to compare to the analysis of fishing communities prepared by the National Marine Fisheries Service (NMFS). Finally, online and phone surveys of fishermen involved in the red snapper fishery were performed to gauge their responses to the change in management. The study reveals a strong correlation between the DEA analysis of fishing communities affected and the analysis performed by NMFS, and reinforces DEA as a method of determining involvement in a fishery. Additionally, the thesis indicates the red snapper IFQ has performed as expected in some areas by its supporters – an average gulf-wide ex-vessel price per pound increase of 10% in just three years; elimination of the rush to fish due to guaranteed quota; and a shift in fleet composition as the number of share owners owning less than 2.00% have dwindled, and the number of shareholders possessing greater than 2.00% of the quota has increased gulf-wide by 50%. However, in other areas such as effort reduction and bycatch rates, the IFQ appears to have mixed results. A reported decline in effort is likely attributable to a reduction in the overall gulf-wide red snapper quota between 2007 and 2008 rather than the IFQ, and even NMFS doubts the bycatch data that are being reported by fishermen. Most importantly, current IFQ shareholders were surveyed via phone and internet revealing not only an overall disapproval by most fishers of the IFQ design process, but also effects contrary to those publicized by IFQ supporters, and a general distrust in fisheries management.

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Secchi, Eduardo Resende, and n/a. "Modelling the population dynamics and viability analysis of franciscana (Pontoporia blainvillei) and Hector�s dolphins (Cephalorhynchus hectori) under the effects of bycatch in fisheries, parameter uncertainty and stochasticity." University of Otago. Department of Zoology, 2006. http://adt.otago.ac.nz./public/adt-NZDU20070118.162020.

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Incidental mortality in fisheries, especially gillnets, is one of the most important causes of decline of many species of cetaceans around the globe. Local populations of franciscana, Pontoporia blainvillei, and Hector�s dolphins, Cephalorhynchus hectori, have been subject to high levels of mortality in gillnets for several decades. This is due to a combination of extensive overlap in distribution of these coastal dolphins and large numbers of fishing nets. Stage-specific population dynamic models (without environmental stochasticity) suggest that both species have a low potential for population growth of approximately 0.2% (95% CI: -3.7% to 4.2%) to 3.4% (95% CI: 1.6% to 6.4%) for franciscana and 0.85% (95% CI: -1.0% to 2.6%) for Hector�s dolphins. Although the two species have similar population growth rates, they result from different life history strategies. Franciscana has a relatively low adult survival rate (0.86; SD = 0.016) which is compensated by a relatively high reproductive potential. The latter is a combination of early reproduction and high fecundity. Hector�s dolphin has a low reproductive potential, which is a combination of late reproduction and low fecundity, which is probably compensated by a relatively high adult survival rate (0.92; SD = 0.02) Apparent differences in growth rate among franciscana populations are possibly due to a combination of varying population-specific reproductive potential and, in some populations, inaccuracy in parameter estimates. Inaccuracy in estimating natural survival rates is also a cause for the low growth rate of Hector�s dolphins. The estimated low population growth rates of these species are insufficient to compensate for current levels of fishing-related mortality in some local populations, especially when environmental and/or demographic stochasticity is considered. Under these circumstances Banks Peninsula population would have a negative mean population growth rate of 0.54% (95% CI: -2.2% to 0.9%) and would decrease below its initial size in approximately 74% of the simulations. Stochasticity alone would decrease considerably the probability of the Banks Peninsula population to grow and recover from past and current high bycatch levels. Effects of stochasticity were also high for one of the franciscana stocks (i.e. stock from Franciscana Management Area II). In other areas (e.g. West Coast of the South Island; franciscana stock from FMA I) fishing effort and bycatch mortality rate seem not to be impeding population growth. Even in a stochastic environment and under current levels of fishing effort, the West Coast population and the franciscana stock from FMA I would grow at a positive rate of 0.32% (95% CI: -1.2% to 1.8%) and 3.1% (95% CI: 2.2 to 7.2%), respectively. Parameter uncertainty does not change the conclusion that immediate and extreme limitations on fishing practice and effort are necessary to increase the chances of recovery for some local populations/stocks. Fishing effort in New Zealand is regulated by a quota system. The quota system, the low number of fishing boats and the relatively low overlap between fishing nets and dolphins are probably the reasons for the positive population growth of Hector�s dolphins from the West Coast of the South Island. On the other hand, not even the Marine Mammal Sanctuary is sufficient to avoid negative mean population growth rate of Hector�s dolphins under current levels of fishing effort off Banks Peninsula. In Brazil, Uruguay and Argentina, where franciscana occurs, gillnet fisheries are not regulated. In some areas, faced with a declining fish stocks, fishermen have increased fishing effort to compensate for reduced catches, and the bycatch of franciscana has increased as a consequence. Strategies aiming at the conservation of these two species are likely to benefit other components of the ecosystem. Especially in the case of franciscana, reducing fishing effort is likely to promote the recovery of depleted fish stocks.

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Eustis, Scott P. "Bycatch of the Lake Pontchartrain Basin inshore shrimp fishery and its effect on two sea catfish species: the gafftopsail catfish (Bagre marinus) and the hardhead catfish (Ariopsis felis)." ScholarWorks@UNO, 2011. http://scholarworks.uno.edu/td/1419.

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In Lake Pontchartrain Basin, commercial fishing in estuarine habitats impacts many non-target species collected as bycatch. I investigated the bycatch assemblages collected by commercial vessels and compared these to assemblages collected by typical fishery-independent methods. I compared assemblages using analysis of similarity (ANOSIM) and determined important species by weight and abundance using similarity percentages analyses (SIMPER). I also examined differences in size-class distributions by gear type using density kernel plots and Mann-Whitney U tests. The two gear types collected significantly different assemblages (ANOSIM R = 0.522, p = 0.001) and gear type explained more composition differences than other factors such as month, daytime, or location. Fishery-independent gear underestimated the importance of many species. Although fishery-independent data are invaluable for monitoring assemblage dynamics, fishery-independent gear collects different assemblages than commercial gear. Larger fishes of important species were caught less often in bycatch, but completely absent from fishery-independent gear.

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