Journal articles on the topic 'Bycatch'
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1
Yonvitner, Yonvitner, Rahmat Kurnia, Mennofatria Boer, Helmy Akbar, and Surya Gentha Akmal. "Kerentanan Bycatch Tuna Dari Perikanan Handline di Selatan Samdera Hindia: Pencatatan Pelabuhan Sendang Biru-Malang." Tropical Fisheries Management Journal 4, no. 2 (December 31, 2020): 66–78. http://dx.doi.org/10.29244/jppt.v4i2.32945.
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Bycatch tuna merupakan komoditas ikan komersial penting dalam perikanan tuna Samudera Hindia. Aktivitas penangkapan bycatch tuna juga berdampak pada penurunan stok sehingga menjadi rentan dan potensial tidak berkelanjutan. Penelitian ini dilakukan di Sendangbiru Malang pada Bulan Juli 2013. Analisis kerentanan dengan pendekatan jarak Euclidean dengan data produkitivitas dan susceptabilitas menggunakan software PSA NOAA. Hasil tangkap bycacth tuna adalah ikan cakalang (Katsuwonus pelamis), Ikan lemadang (Coryphaena hippurus), baby tuna (Thunnus albacores). Hasil kerentana menunjukan tingkat kerentanan yang diperoleh sebesar 1,66 untuk baby tuna, 1,27 untuk lemadang dan 1,42 untuk cakalang. Secara keseluruhan nilai indek kerentanan masih rendah dari 1,8 dimana stok tergolong rentan rendah dan potensi ikan bycatch tuna masih berpotensi berkelanjutan di Sendang Biru.
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Anderson, Owen F., and Malcolm R. Clark. "Analysis of bycatch in the fishery for orange roughy, Hoplostethus atlanticus, on the South Tasman Rise." Marine and Freshwater Research 54, no. 5 (2003): 643. http://dx.doi.org/10.1071/mf02163.
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Government fisheries observers made detailed records of the catch weights of all species caught on 545 trawls between October 1997 and August 2000 in the South Tasman Rise orange roughy (Hoplostethus atlanticus) fishery. Bycatch ratios, the ratio of bycatch weight to tow duration, were derived from these data and used to make estimates of total annual bycatch for several species groups. Bycatch ratios based on tow duration were chosen over ratios based on orange roughy catch weights after comparing the coefficients of variation (c.v.) of sets of trial data. Bycatch ratios and total bycatch were estimated for three species of oreos (Oreosomatidae), corals and all other bycatch species combined, for the fishing years from 1997–1998 to 2000–2001. Total oreo bycatch dropped from about 7400 t to less than 350 t during this time. These estimates agreed well with recorded oreo landings data for three of the four years. There was a considerable bycatch of corals, with both the bycatch ratio and the total bycatch reducing during the period examined, the latter from about 1750 t to 100 t per year. The coral bycatch comprised a large number of species, but was dominated by the reef-forming stony coral Solenosmilia variabilis. Annual bycatch of all other species combined, mainly rattails (Macrouridae) and dogfishes (Squalidae), was low (13–120 t). Bycatch of this group dropped sharply in each year as the result of a combination of decreasing bycatch ratio and decreasing fishing effort.
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Winther, Morten. "Bycatches of harbour porpoises (Phocoena phocoena L.) in Danish set-net fisheries." J. Cetacean Res. Manage. 1, no. 2 (January 25, 1999): 123–35. http://dx.doi.org/10.47536/jcrm.v1i1.457.
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Data on bycatch of harbour porpoise (Phocoena phocoena L.) in the commercial Danish set-net fisheries were sampled from 5,591km nets in the period 1992 to 1998 using independent observers. A total bycatch of 325 harbour porpoises was reported. Cluster analysis was used to stratify the sampled fishing trips and official catch statistics into a number of different m6tiers defined by the target species for the trips. Extrapolation of the observed bycatch rate to total fish landings of the Danish set-net fleet gave an average annual bycatch of 6,785 (CV 0.12) for the North Sea fisheries in the period 1994-1998. Sampling was not sufficient to estimate total bycatch for other areas. Bycatch was observed in Kattegat but not in the Baltic Sea. Generalised Linear Models were used to identify significant factors for bycatch in the North Sea. The bycatch rate, given as number per length of nets x soak time, was significantly lower in fisheries for flatfish compared to roundfish fisheries. The highest bycatch rate was in the cod fishery over wrecks and no bycatch was observed in the sole fishery. Significant seasonal variation of bycatch was identified with the highest bycatch rate in the first and third quarter of the year. Bycatch rates had not changed in the observed period and there was no significant difference in bycatch rates between sub-areas.
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Brock, Daniel J., Peter J. Hawthorne, Timothy M. Ward, and Adrian J. Linnane. "Two monitoring methods that assess species composition and spatio-temporal trends in bycatch from an important temperate rock lobster (Jasus edwardsii) fishery." Marine and Freshwater Research 58, no. 3 (2007): 273. http://dx.doi.org/10.1071/mf06061.
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The effectiveness of two monitoring programs, designed to describe and quantify the bycatch from commercial pots, was examined in the South Australian rock lobster (Jasus edwardsii) fishery (SARLF). The first, logbook sampling, relied on information collected and recorded by fishers in logbooks. The second, bycatch sampling, required fishers to collect bycatch specimens on a nominated day for later scientific analysis. A total of 40 bycatch species were recorded during the study. Finfish, mainly blue-throat wrasse (Notolabrus tetricus) and leather jacket species (Meuschenia hippocrepis and Meushenia australis), were the major component (>90% by number). Data from the logbook program were appropriate for monitoring spatio-temporal trends in bycatch, whereas the bycatch sampling provided more accurate information on bycatch species. Each program was subject to bias when estimating total bycatch numbers and, as a result, a combination of both methods indicated a cost-effective and appropriate way with which to monitor bycatch from the fishery. In comparison with other fisheries, bycatch from the SARLF was relatively low; however, because bycatch was dominated by relatively few species, ongoing monitoring and risk assessment of these populations is needed to ensure long-term sustainability of bycatch levels.
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Walmsley, Sarah A., Rob W. Leslie, and Warwick H. H. Sauer. "Managing South Africa's trawl bycatch." ICES Journal of Marine Science 64, no. 2 (November 13, 2006): 405–12. http://dx.doi.org/10.1093/icesjms/fsl022.
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Abstract Walmsley, S. A., Leslie, R. W., and Sauer, W. H. H. 2007. Managing South Africa's trawl bycatch. – ICES Journal of Marine Science, 64: 405–412. Over the past few decades, it has become widely recognized that the management strategies of world fisheries must ensure sustainability of bycatch as well as of target species. South Africa implemented a pilot observer programme from 1995 to 2000 to collect data on the levels and patterns of bycatch and discards in the demersal trawl fishery. Here, the results of that programme are used in conjunction with information on bycatch value and compliance to assess the issues and problems regarding bycatch and discarding in the fishery. In general, bycatch components can be placed into one of three categories (discarded bycatch, retained bycatch, and processing waste), each of which present different management problems and require different management approaches. The results were used to formulate a bycatch management plan for the demersal trawl fishery in South Africa. Given the need to continue monitoring bycatch, the performance of the pilot observer programme is reviewed, and the levels of sampling effort required for a national programme are discussed.
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LEBRETON, JEAN-DOMINIQUE, and SOPHIE VÉRAN. "Direct evidence of the impact of longline fishery on mortality in the Black-footed Albatross Phoebastria nigripes." Bird Conservation International 23, no. 1 (July 4, 2012): 25–35. http://dx.doi.org/10.1017/s0959270912000299.
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SummaryThe incidental bycatch of seabirds in longline fisheries is one of the most striking examples of diffuse and incidental impact of human activities on vertebrate species. While there are various types of evidence of a strong impact of longline fisheries on seabirds, in particular albatrosses, the incidental bycatch mortality has never been directly linked to estimates of bycatch derived from on-board surveys. We develop a capture-recapture analysis which relates the annual probability of survival in the Black-Footed Albatross to the estimated absolute bycatch. By converting the absolute bycatch into an estimate relative to population size and using the theory of exploited populations, we show that survival probability decreases linearly with bycatch, and that the bycatch is underestimated by at least 50%, confirming suspicions based on reviews of the bycatch survey procedures, and raising further concerns about the impact of longline fisheries on seabirds.
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Fangel, Kirstin, Kim Magnus Bærum, Signe Christensen-Dalsgaard, Øystein Aas, and and Tycho Anker-Nilssen. "Incidental bycatch of northern fulmars in the small-vessel demersal longline fishery for Greenland halibut in coastal Norway 2012–2014." ICES Journal of Marine Science 74, no. 1 (September 26, 2016): 332–42. http://dx.doi.org/10.1093/icesjms/fsw149.
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With seabird populations in rapid decline, understanding and reducing anthropogenic mortality factors is essential. One such factor is incidental bycatch in fisheries. Here we analyze bycatch in the small-vessel demersal longline fishery for Greenland halibut outside the coast of Northern Norway in 2012–2014, by means of self-reporting from fishers and independent observers. A sample of killed birds were analysed for sex, age, reproductive status and condition. Nearly all were northern fulmars. Estimated total bycatch for this fishery for the 3-year period was about 312 birds (SE ≈ 133) using a stratified estimator. Bycatch rate per 1000 hooks was estimated to approximately 0.031 (SE ≈ 0.012). Exploring per trip bycatch rates utilizing generalized linear mixed models, we found no convincing trends of environmental, spatial and temporal variables in explaining bycatch. However, trips using longlines with non-swivel hooks had a more than 100-fold larger bycatch rate (mean ≈ 0.760, SE ≈ 0.160) than those using swivel hooks (mean ≈ 0.008, SE ≈ 0.002). Further, trips with external observers had higher bycatch estimates (mean ≈ 0.75, SE ≈ 0.16) compared with trips where bycatch was registered by the fishers (mean ≈ 0.02, SE < 0.01). Of the analysed birds, about two-thirds were adult birds and males dominated (71.1%). A majority were in good or moderate condition. The findings suggest that the incidental bycatch in the Greenland halibut fishery along the Norwegian coast is more limited than previous studies indicated, and that the use of swivel hooks can significantly reduce such bycatch. However, the impacts on the red-listed, diminishing population of fulmars breeding in mainland Norway should be assessed further and requires a method to assign killed birds to regions/colonies. Also, gaining a better understanding of what triggers events with extreme bycatch numbers is important to reduce the problem further and to improve bycatch modelling.
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Watson, John, Daniel Foster, Scoll Nichols, Arvlnd Shah, Elizabeth Scoll-oenlon, and James Nanc. "The Development of Bycatch Reduction Technology in the Southeastern United States Shrimp Fishery." Marine Technology Society Journal 33, no. 2 (January 1, 1999): 51–56. http://dx.doi.org/10.4031/mtsj.33.2.8.
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Shrimp trawl bycatch is a significant source of fishery induced mortality for managed species including red snapper (Lutjanus campechanus Poey), Spanish mackerel (Scomberomorus maculatus MitcheU), and weakfish (Cynoscion regalis Baloch, Schneider) in the southeastern United States. These species have been overfished and are under both state and federal management plans which include regulations mandating reduction of shrimp trawl bycatch mortality. In 1990 the U.S. Congress passed amendments to the Magnuson Fishery Conservation and Management Act (16 U.S.C. 1854) which called for a research program that included the design and evaluation of approaches for reducing shrimp trawl bycatch mortality. A strategic planning initiative addressing finfish bycatch in the Gulf of Mexico and southeastern Atlantic shrimp fisheries was developed by the Gulf and South Atlantic Fisheries Foundation through funding and guidance provided by the National Marine Fisheries Service. A cooperative research plan was developed in 1992 which included the identification, development, and evaluation of gear options for reducing bycatch in the Gulf of Mexico and southeastern Atlantic shrimp fisheries. Between 1990 and 1996 one hundred and forty five bycatch reduction conceptual gear designs contributed by fishers, net shops, gear technicians, and biologists were evaluated. Sixteen of these designs were tested on cooperative commercial shrimp vessels by observers under the southeast regional cooperative bycatch program. Analyses of data from commercial vessel testing indicates that two bycatch reduction designs have potential to significantly reduce shrimp trawl bycatch for weakfish and Spanish mackerel in the southeastern Atlantic and two designs have the potential to significantly reduce red snapper bycatch in the Gulf of Mexico. The fisheye and the extended funnel bycatch reduction devices have been mandated for use in the southeastern Atlantic shrimp fishery and the fisheye and Jones/Davis bycatch reduction devices have been mandated for use in the Gulf of Mexico shrimp trawl fishery.
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Kot, Connie Y., Andre M. Boustany, and Patrick N. Halpin. "Temporal patterns of target catch and sea turtle bycatch in the US Atlantic pelagic longline fishing fleet." Canadian Journal of Fisheries and Aquatic Sciences 67, no. 1 (January 2010): 42–57. http://dx.doi.org/10.1139/f09-160.
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Sea turtle bycatch in pelagic longline fishing gear is an ongoing threat to the conservation of sea turtle populations. However, these bycatch events do not occur uniformly in space or time. Leatherback ( Dermochelys coriacea ) and loggerhead ( Caretta caretta ) bycatch rates reported in large fishing regions exhibited different degrees of interannual variability. Target catch and sea turtle bycatch in most regions displayed strong periodicity that corresponded to seasons (~365 days) and/or moon phase (~29 days). When trends in catch and bycatch rates were examined by month and moon phase, the significant periods of higher and lower catch and bycatch related to swordfish ( Xiphias gladius ), yellowfin tuna ( Thunnus albacares ), and sea turtle temporal distributions in foraging and spawning/nesting, oceanographic and prey conditions, and foraging behavior. Catch and bycatch rates tended to depend more on a seasonal rather than a lunar time scale, although there is likely an interaction between the two. These findings provide insights to the susceptibility of target catch and bycatch, regional and temporal patterns of fishing effort, and potential guidance for resource management and conservation.
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Cosandey-Godin, Aurelie, Elias Teixeira Krainski, Boris Worm, and Joanna Mills Flemming. "Applying Bayesian spatiotemporal models to fisheries bycatch in the Canadian Arctic." Canadian Journal of Fisheries and Aquatic Sciences 72, no. 2 (February 2015): 186–97. http://dx.doi.org/10.1139/cjfas-2014-0159.
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Understanding and reducing the incidence of accidental bycatch, particularly for vulnerable species such as sharks, is a major challenge for contemporary fisheries management. Here we establish integrated nested Laplace approximations (INLA) and stochastic partial differential equations (SPDE) as two powerful tools for modelling patterns of bycatch through time and space. These novel, computationally fast approaches are applied to fit zero-inflated hierarchical spatiotemporal models to Greenland shark (Somniosus microcephalus) bycatch data from the Baffin Bay Greenland halibut (Reinhardtius hippoglossoides) gillnet fishery. Results indicate that Greenland shark bycatch is clustered in space and time, varies significantly from year to year, and there are both tractable factors (number of gillnet panels, total Greenland halibut catch) and physical features (bathymetry) leading to the high incidence of Greenland shark bycatch. Bycatch risk could be reduced by limiting access to spatiotemporal hotspots or by establishing a maximum number of panels per haul. Our method explicitly models the spatiotemporal correlation structure inherent in bycatch data at a very reasonable computational cost, such that the forecasting of bycatch patterns and simulating conservation strategies becomes more accessible.
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Cruz, Maria João, Miguel Machete, Gui Menezes, Emer Rogan, and Mónica A. Silva. "Estimating common dolphin bycatch in the pole-and-line tuna fishery in the Azores." PeerJ 6 (February 12, 2018): e4285. http://dx.doi.org/10.7717/peerj.4285.
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Small-scale artisanal fisheries can have a significant negative impact in cetacean populations. Cetacean bycatch has been documented in the pole-and-line tuna fishery in the Azores with common dolphins being the species more frequently taken. Based on data collected by observers on ∼50% of vessels operating from 1998 to 2012, we investigate the influence of various environmental and fisheries-related factors in common dolphin bycatch and calculate fleet-wide estimates of total bycatch using design-based and model-based methods. Over the 15-year study dolphin bycatch occurred in less than 0.4% of the observed fishing events. Generalized additive modelling results suggest a significant relationship between common dolphin bycatch and duration of fishing events, sea surface temperature and location. Total bycatch calculated from the traditional stratified ratio estimation approach was 196 (95% CI: 186–205), while the negative binomial GAM estimated 262 (95% CI: 249–274) dolphins. Bycatch estimates of common dolphin were similar using statistical approaches suggesting that either of these methods may be used in future bycatch assessments for this fishery. Our work shows that rates of common dolphin bycatch in the pole-and-line tuna fishery in the Azores are low, despite considerable variations between years. Dolphins caught were released alive although the fate of these individuals is unknown. Continued monitoring will provide a better understanding of dolphin bycatch and more accurate estimates essential in the development of potential mitigation measures.
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Drakopulos, Lauren. "New Materialist Approaches to Fisheries." Environment and Society 11, no. 1 (September 1, 2020): 100–114. http://dx.doi.org/10.3167/ares.2020.110107.
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For the past 40 years, bycatch has been a significant focus of fisheries science and management, yet bycatch has evaded clear definition persisting as a perennial fisheries concern. This article brings insights from new materialism to examine the ontological politics of bycatch. Building on new materialist approaches to oceans and fisheries, the article contributes to the bycatch debate by putting forth a new framework for understanding bycatch as multiple, enacted through the material-discursive practices of science and policy. Through a survey of policy and scientific documents, the article traces the emergence of “bycatch” as a global fisheries issue. The analysis broadens the orderings and normative understandings about human and nonhuman life inflected by post-humanist and new materialist traditions, as well as fisheries science and policy.
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Brennecke, Dennis, Magnus Wahlberg, Anita Gilles, and Ursula Siebert. "Age and lunar cycle predict harbor porpoise bycatch in the south-western Baltic Sea." PeerJ 9 (October 27, 2021): e12284. http://dx.doi.org/10.7717/peerj.12284.
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The harbor porpoise, Phocoena phocoena, is the only cetacean regularly occurring in the Baltic Sea. During the last decades, several anthropogenic activities have affected porpoises in the Baltic region. Most notably is bycatch in static fishing gear, such as gill nets, which is the main human-induced cause of death in odontocetes. There is still considerable uncertainty about which factors influence the amount of bycatch. In the present study, we reviewed bycatch data collected from 1987 to 2016 from the south-western Baltic Sea. There was a significant difference in bycatch due to seasonality and region, and there was a higher bycatch rate in juveniles than in adults. The only abiotic factor associated with bycatch was the lunar cycle, with more animals bycaught during a full moon. These results improve our understanding of which biotic and abiotic factors are associated with bycatch of Baltic harbor porpoises, which can be used to strengthen conservation endeavors such as managing fishing efforts.
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Parsa, Mahdi, Timothy J. Emery, Ashley J. Williams, and Simon Nicol. "An empirical Bayesian approach for estimating fleet- and vessel-level bycatch rates in fisheries with effort heterogeneity and limited data: a prospective tool for measuring bycatch mitigation performance." ICES Journal of Marine Science 77, no. 3 (February 27, 2020): 921–29. http://dx.doi.org/10.1093/icesjms/fsaa020.
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Abstract Minimizing fishing-induced mortality on bycatch and endangered, threatened or protected species is a necessity for fisheries managers. Estimating individual vessel bycatch rates by dividing the amount of bycatch by effort (nominal rate) can be biased, as it does not consider effort heterogeneity within the fleet and ignores prior knowledge of fleet bycatch rates. We develop an empirical Bayesian approach for estimating individual vessel and fleet bycatch rates that: (i) considers effort heterogeneity among vessels and; (ii) pools data from similar vessels for more accurate estimation. The proposed standardized bycatch rate of a vessel is, therefore, the weighted average of the pool rate and nominal rate of the vessel; where the weights are functions of the vessel’s fishing effort and a constant estimated from the model. We apply this inference method to the estimation of seabird bycatch rates in the component of the Australian Eastern Tuna and Billfish Fishery targeting yellowfin tuna. We illustrate the capability of the method for providing fishery managers with insights on fleet-wide bycatch mitigation performance and the identification of outperforming and underperforming vessels. This method can also be used by fishery managers to develop fleet-wide performance measures or quantitative evaluation standards.
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Mangel, Jeffrey C., John Wang, Joanna Alfaro-Shigueto, Sergio Pingo, Astrid Jimenez, Felipe Carvalho, Yonat Swimmer, and Brendan J. Godley. "Illuminating gillnets to save seabirds and the potential for multi-taxa bycatch mitigation." Royal Society Open Science 5, no. 7 (July 2018): 180254. http://dx.doi.org/10.1098/rsos.180254.
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Bycatch in net fisheries is recognized as a major source of mortality for many marine species, including seabirds. Few mitigation solutions, however, have been identified. We assessed the effectiveness of illuminating fishing nets with green light emitting diodes (LEDs) to reduce the incidental capture of seabirds. Experiments were conducted in the demersal, set gillnet fishery of Constante, Peru and compared 114 pairs of control and illuminated nets. We observed captures of a total of 45 guanay cormorants ( Phalacrocorax bougainvillii ), with 39 caught in control nets and six caught in illuminated nets. Seabird bycatch in terms of catch-per-unit-effort was significantly ( p < 0.05) higher in control nets than in illuminated nets, representing an 85.1% decline in the cormorant bycatch rate. This study, showing that net illumination reduces seabird bycatch and previous studies showing reductions in sea turtle bycatch without reducing target catch, indicates that net illumination can be an effective multi-taxa bycatch mitigation technique. This finding has broad implications for bycatch mitigation in net fisheries given LED technology's relatively low cost, the global ubiquity of net fisheries and the current paucity of bycatch mitigation solutions.
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Zhou, Can, and Baochao Liao. "Assessing the Uncertainty of Total Seabird Bycatch Estimates Synthesized from Multiple Sources with a Scenario Analysis from the Western and Central Pacific." Birds 3, no. 3 (August 10, 2022): 260–76. http://dx.doi.org/10.3390/birds3030017.
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Each year, billions of seabirds undertake migrations, connecting remote regions of the world, potentially synchronizing population fluctuations among distant areas. This connectedness has implications for the uncertainty calculations of the total seabird bycatch estimate at a regional/global scale. Globally, fisheries bycatch poses a major problem in fishery management, and estimating the uncertainty associated with a regional/global seabird bycatch estimate is important because it characterizes the accuracy and reliability of the fisheries’ impact on the seabird populations. In this study, we evaluate different assumptions underlying the estimation of the variability of the total seabird bycatch at a regional/global scale based on local assessment reports. In addition to theoretical analysis, we also simulate multiple spatially distant separately managed areas with relatively low levels of observer coverage, based on bycatch data from the Western and Central Pacific Fisheries Commission convention area. The results show that assuming a completely synchronized variation produced the most conservative uncertainty estimate and it also missed an opportunity to improve the precision. Simplified correlation structures also failed to capture the complex dynamics of bycatch rates among spatially distant areas. It is recommended to empirically estimate the correlation of bycatch rates between each pair of sources based on bycatch rate time series.
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Stock, Brian C., Eric J. Ward, James T. Thorson, Jason E. Jannot, and Brice X. Semmens. "The utility of spatial model-based estimators of unobserved bycatch." ICES Journal of Marine Science 76, no. 1 (October 25, 2018): 255–67. http://dx.doi.org/10.1093/icesjms/fsy153.
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Abstract Quantifying effects of fishing on non-targeted (bycatch) species is an important management and conservation issue. Bycatch estimates are typically calculated using data collected by on-board observers, but observer programmes are costly and therefore often only cover a small percentage of the fishery. The challenge is then to estimate bycatch for the unobserved fishing activity. The status quo for most fisheries is to assume the ratio of bycatch to effort is constant and multiply this ratio by the effort in the unobserved activity (ratio estimator). We used a dataset with 100% observer coverage, 35 440 hauls from the US west coast groundfish trawl fishery, to evaluate the ratio estimator against methods that utilize fine-scale spatial information: generalized additive models (GAMs) and random forests. Applied to 15 species representing a range of bycatch rates, including spatial locations improved model predictive ability, whereas including effort-associated covariates generally did not. Random forests performed best for all species (lower root mean square error), but were slightly biased (overpredicting total bycatch). Thus, the choice of bycatch estimation method involves a tradeoff between bias and precision, and which method is optimal may depend on the species bycatch rate and how the estimates are to be used.
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Hamilton, Sheryl, and G. Barry Baker. "Population growth of an endangered pinniped—the New Zealand sea lion (Phocarctos hookeri)—is limited more by high pup mortality than fisheries bycatch." ICES Journal of Marine Science 76, no. 6 (March 28, 2019): 1794–806. http://dx.doi.org/10.1093/icesjms/fsz039.
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Abstract The endangered New Zealand sea lion, Phocarctos hookeri is killed as incidental bycatch in a trawl fishery operating near their second largest population on Campbell Island in New Zealand’s sub-Antarctic. Using the Potential Biological Removal (PBR) procedure to assess the sustainability of this bycatch for the sea lion population on Campbell Island indicated that annual bycatch estimates, particularly following the implementation of bycatch mitigation measures, are below the PBR threshold of 25 (derived using a precautionary approach). Preliminary Population Viability Analysis (PVA) modelling supported the finding that current bycatch levels, especially given a strong male bias (98%) in bycatch, are sustainable for this population. Models showed that reducing pup mortality through management actions, such as installing ramps in wallows where large numbers of pups drown, would lead to increased population growth. While obtaining more accurate data on population status and demographic parameters for the Campbell Island population should be a priority, this will take many years of research. The PBR and PVA tools demonstrate that contemporary conservation management should continue to focus on increasing pup survival while maintaining mitigation approaches that have reduced bycatch to low levels, together with high observer coverage to sustain confidence in annual bycatch estimates.
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Stock, Brian C., Eric J. Ward, Tomoharu Eguchi, Jason E. Jannot, James T. Thorson, Blake E. Feist, and Brice X. Semmens. "Comparing predictions of fisheries bycatch using multiple spatiotemporal species distribution model frameworks." Canadian Journal of Fisheries and Aquatic Sciences 77, no. 1 (January 2020): 146–63. http://dx.doi.org/10.1139/cjfas-2018-0281.
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Spatiotemporal predictions of bycatch (i.e., catch of nontargeted species) have shown promise as dynamic ocean management tools for reducing bycatch. However, which spatiotemporal model framework to use for generating these predictions is unclear. We evaluated a relatively new method, Gaussian Markov random fields (GMRFs), with two other frameworks, generalized additive models (GAMs) and random forests. We fit geostatistical delta-models to fisheries observer bycatch data for six species with a broad range of movement patterns (e.g., highly migratory sea turtles versus sedentary rockfish) and bycatch rates (percentage of observations with nonzero catch, 0.3%–96.2%). Random forests had better interpolation performance than the GMRF and GAM models for all six species, but random forests performance was more sensitive when predicting data at the edge of the fishery (i.e., spatial extrapolation). Using random forests to identify and remove the 5% highest bycatch risk fishing events reduced the bycatch-to-target species catch ratio by 34% on average. All models considerably reduced the bycatch-to-target ratio, demonstrating the clear potential of species distribution models to support spatial fishery management.
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Lobo, Aaron Savio. "The Bycatch problem." Resonance 12, no. 5 (May 2007): 60–70. http://dx.doi.org/10.1007/s12045-007-0051-0.
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Mendo, Jaime, Tania Mendo, Patricia Gil-Kodaka, Jimmy Martina, Iván Gómez, Ruggeri Delgado, Jhenifer Fernández, et al. "Bycatch and discards in the artisanal shrimp trawl fishery in Northern Peru." PLOS ONE 17, no. 6 (June 22, 2022): e0268128. http://dx.doi.org/10.1371/journal.pone.0268128.
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This study analyses the bycatch composition of an artisanal shrimp trawl fleet operating between Cabo Blanco and Máncora in Northern Peru between April 2019 and March 2020. A total of 300 hauls were analysed with respect to target catch and bycatch (consisting of other commercial species, discards, and macroalgae). A total of 277 species were recorded including 111 species of fish, 65 species of molluscs, 51 species of crustaceans, 22 species of algae, 12 species of cnidarian, 9 species of echinoderms, 4 species of Bryozoa and 3 species of polychaeta. Capture per unit effort (CPUE, kg.h-1) was highest for fish, followed by crustaceans, algae and molluscs. The target species Penaeus californiensis coffee shrimp constituted 17.8% of the overall catch,82.2% represented bycatch, and 50.6% represented discards. Coffee shrimps were more abundant in June and November 2019 and in January and February 2020. Highest bycatch CPUE occurred in May, June and December 2019. The most abundant species in the bycatch throughout the study period were sand perch (Diplectrum conceptione, 16% weight of the total catch), the macroalgae caulerpa (Caulerpa filiformis, 13%), sole flounder (Etropus ectenes, 6.4%), Pacific drum (Larimus pacificus, 5.7%), and lumptail searobin (Prionotus stephanophrys, 5.1%). Overall, the contribution of sand perch and flounder, exceeded the weight of coffee shrimp, therefore the interpretation that shrimp is the sole target species needs to be revised. The number of discarded species per month increased towards the spring months with the highest value in November. This study represents the first characterisation of bycatch in the artisanal trawling fishery in the Piura region in northern Peru and reveals a high proportion of bycatch in the fishery but also hints at potential temporal management measures that could be imposed to reduce the levels of bycatch. For example, the months of May and December had the greatest bycatch to shrimp ratios and the fishery could potentially be closed to avoid high bycatch risk, however, longer term information is needed to assess if the trends observed in bycatch are similar over longer periods of time. The species characterisation of bycatch also provides information for the design of modified nets which would target the reduction of small fish present in the catch.
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Passadore, Cecilia, Andrés Domingo, and Eduardo R. Secchi. "Analysis of marine mammal bycatch in the Uruguayan pelagic longline fishery operating in the Southwestern Atlantic Ocean." ICES Journal of Marine Science 72, no. 5 (January 22, 2015): 1637–52. http://dx.doi.org/10.1093/icesjms/fsu250.
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Abstract Bycatch is one of the main causes of human-caused mortality and population decline of many marine mammals. Monitoring bycatch is the first step to understand the impact of the fisheries on the species affected. Understanding how the interaction between marine mammals and fishing operations varies in space and time, and how it is influenced by environmental variables, is essential for designing mitigation strategies to reduce bycatch mortality. In this paper, we use data gathered by scientific observers and a fishing skipper to analyse marine mammals bycatch by the Uruguayan pelagic longline fishery operating in the Southwestern Atlantic Ocean from 1996 to 2007. The total bycatch per unit effort (Bcpue) was 0.0150 marine mammals/1000 hooks and the highest values (∼0.2) were recorded between 37°–38°S and 49°–51°W. Total cetacean Bcpue during the study period was low (0.0051 cetacean/1000 hooks) and occurred between 32°–37°S and 46°–54°W. Generalized additive models showed that cetaceans' bycatch was mainly affected by the depth, sea surface temperature, and season. Although cetaceans were captured year-round, the highest values were registered in spring months, most bycatch events occurred over the continental slope (median = 619 m) and in waters with a median temperature of 19.7°C. The bycatch of pinnipeds was influenced by depth, location, and season. Pinniped bycatch occurred mainly in winter, in waters ranging from 80 to 5000 m of depth (median = 2366 m) between 34°–37°S (median = 35.9°S) and 54°–49°W (median = 51.8°W). The spatial analysis showed that most bycatch events occurred within the Brazil–Malvinas Confluence zone, an area of high productivity where the pelagic longline fleet concentrates its fishing effort and where marine mammals probably concentrate to feed.
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Hines, E., LS Ponnampalam, C. Junchompoo, C. Peter, L. Vu, T. Huynh, M. Caillat, et al. "Getting to the bottom of bycatch: a GIS-based toolbox to assess the risk of marine mammal bycatch." Endangered Species Research 42 (June 4, 2020): 37–57. http://dx.doi.org/10.3354/esr01037.
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Marine mammal bycatch poses a particular challenge in developing countries, where data to document bycatch and its effects are often lacking. Using the Bycatch Risk Assessment (ByRA) toolkit, based on InVEST open-source models, we chose 4 field sites in Southeast Asia with varying amounts of data on marine mammals and fishing occurrence: Trat province in the eastern Gulf of Thailand, the Sibu-Tinggi Islands and Kuching Bay, Malaysia, and Kien Giang Biosphere Reserve in southwestern Vietnam. These field sites have similar species of coastal marine mammals, small-scale and commercial fisheries, and support for research from universities and/or management. In Thailand and Kuching, results showed changing patterns of fishing and Irrawaddy dolphin Orcaella brevirostris habitat use across seasons, showing how bycatch risk could change throughout the year. Risk maps for dugongs Dugong dugon in peninsular Malaysia highlighted patterns of bycatch risk concentrated around a mainland fishing pier, and revealed high risk in a northern subregion. In Vietnam, first maps of bycatch risk for the Irrawaddy dolphin showed the highest risk driven by intensive use of gillnets and trawling gear. ByRA pinpointed areas of spatial and seasonal bycatch exposure, and estimated the consequence of bycatch on local species, providing managers with critical information on where to focus bycatch mitigation and meet new global standards for US Marine Mammal Protection Act and other international regulation (e.g. Official Journal of the European Union 2019; Regulation 2019/1241) compliance. The toolbox, a transferable open-source tool, can be used to guide fisheries management, marine mammal conservation, spatial planning, and further research.
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Bäcklin, Britt-Marie, Charlotta Moraeus, Anna Roos, Eva Eklöf, and Ylva Lind. "Health and age and sex distributions of Baltic grey seals (Halichoerus grypus) collected from bycatch and hunt in the Gulf of Bothnia." ICES Journal of Marine Science 68, no. 1 (August 25, 2010): 183–88. http://dx.doi.org/10.1093/icesjms/fsq131.
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Abstract Bäcklin, B-M., Moraeus, C., Roos, A., Eklöf, E., and Lind, Y. 2011. Health and age and sex distributions of Baltic grey seals (Halichoerus grypus) collected from bycatch and hunt in the Gulf of Bothnia. – ICES Journal of Marine Science, 68: 183–188. Age distribution, sex ratio, and season of death were investigated in grey seals taken as bycatch and hunted in the Gulf of Bothnia for the period 2002–2007. In seals 1–20 years old, certain health variables, earlier reported as parts of a disease complex related to persistent organic pollutants, were also investigated. Most of the hunted group were female (60%), but there were more males (62%) in the bycatch group. In spring, there were more bycatch than hunted yearlings. Seals taken as bycatch were leaner than hunted animals, and in hunted seals, there was a significant seasonal difference in blubber thickness that was not observed in seals taken in the bycatch. The prevalence of intestinal ulcers was 18–50% in bycatch and 24–74% in hunted animals. Hunted males 4–20 years old had a significantly greater prevalence of intestinal ulcers than bycatch males in the same age group. Adrenocortical thickening and mean weight of the adrenals increased with age. No lesions were observed in female reproductive organs, and in autumn, nearly all mature females were pregnant. The main differences between hunted and bycatch grey seals were in the season when death occurred, the prevalence of yearlings, the sex ratio, the blubber thickness, and the prevalence of intestinal ulcers.
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Hasselman, Daniel J., Eric C. Anderson, Emily E. Argo, N. David Bethoney, Stephen R. Gephard, David M. Post, Bradley P. Schondelmeier, Thomas F. Schultz, Theodore V. Willis, and Eric P. Palkovacs. "Genetic stock composition of marine bycatch reveals disproportional impacts on depleted river herring genetic stocks." Canadian Journal of Fisheries and Aquatic Sciences 73, no. 6 (June 2016): 951–63. http://dx.doi.org/10.1139/cjfas-2015-0402.
Full textAbstract:
Bycatch of mid-trophic-level anadromous fishes that connect marine and freshwater ecosystems is a growing conservation concern. Anadromous alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis) are important components of coastal freshwater and marine food webs, but have experienced dramatic declines in the abundances of spawning adults. Freshwater-focused restoration efforts have yielded few consistent signs of recovery, raising concerns that bycatch in Northwest Atlantic commercial fisheries may be negating these conservation actions. Using data from 15 microsatellites genotyped for baseline populations and bycatch, we conducted genetic stock identification to understand how bycatch was partitioned among previously identified regional genetic stocks. We then combined this information with fishery observer data to estimate genetic stock-specific bycatch mortality for the southern New England Atlantic herring fishery (2012–2013). Bycatch overall, but especially in the Atlantic herring fishery, was disproportionately assigned to the most severely depleted genetic stocks (alewife southern New England stock — 70% of assignments; blueback herring mid-Atlantic stock — 78% of assignments). These genetic stocks overlap in the region surrounding Long Island Sound, suggesting that bycatch taken from this area in recent years may be negatively impacting recovery efforts in this region. Our study suggests that mitigating bycatch on the southern New England fishing grounds may benefit recovery efforts for alewife and blueback herring genetic stocks that have experienced the greatest declines in spawning adult abundances.
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Kaplan, Isaac C., Daniel S. Holland, and Elizabeth A. Fulton. "Finding the accelerator and brake in an individual quota fishery: linking ecology, economics, and fleet dynamics of US West Coast trawl fisheries." ICES Journal of Marine Science 71, no. 2 (September 4, 2013): 308–19. http://dx.doi.org/10.1093/icesjms/fst114.
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Abstract Isaac C. Kaplan, Daniel S. Holland, and Elizabeth A. Fulton. 2014. Finding the accelerator and brake in an individual quota fishery: linking ecology, economics, and fleet dynamics of US West Coast trawl fisheries. – ICES Journal of Marine Science, 71: 308–319. In 2011, the Pacific Fisheries Management Council implemented an individual transferrable quota (ITQ) system for the US West Coast groundfish trawl fleet. Under the ITQ system, each vessel now receives transferrable annual allocations of quota for 29 groundfish species, including target and bycatch species. Here we develop an ecosystem and fleet dynamics model to identify which components of an ITQ system are likely to drive responses in effort, target species catch, bycatch, and overall profitability. In the absence of penalties for discarding over-quota fish, ITQs lead to large increases in fishing effort and bycatch. The penalties fishermen expect for exceeding quota have the largest effect on fleet behaviour, capping effort and total bycatch. Quota prices for target or bycatch species have lesser impacts on fishing dynamics, even up to bycatch quota prices of $50 kg−1. Ports that overlap less with bycatch species can increase effort under individual quotas, while other ports decrease effort. Relative to a prior management system, ITQs with penalties for exceeding quotas lead to increased target species landings and lower bycatch, but with strong variation among species. The model illustrates how alternative fishery management policies affect profitability, sustainability and the ecosystem.
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Zhou, Can, and Nigel Brothers. "Interaction frequency of seabirds with longline fisheries: risk factors and implications for management." ICES Journal of Marine Science 78, no. 4 (March 1, 2021): 1278–87. http://dx.doi.org/10.1093/icesjms/fsab014.
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Abstract Fishery bycatch poses a serious threat to seabird populations globally. Traditional haul-only post-capture observations are inadequate and inefficient to document seabird bycatch due to the substantial bycatch loss known to occur. Pre-capture observations offer an alternative by documenting seabird interactions leading up to captures. Based on the long-term large-scale dedicated field observations, this study revealed significant risk factors for the pre-capture stages of the seabird bycatch process in pelagic longline fisheries using Bayesian methods. Rough sea conditions were found to correlate with more seabirds following fishing vessels. Species identity, density effect, inter-species effect, and sea condition were found to significantly affect how frequently seabirds aggregated around a fishing vessel engage in bait-taking interactions. Intra-species competition was found to be the dominant type of density effect. Moreover, a web of inter-species interactions was identified to facilitate the bait-taking of superior competitors at the expense of inferior ones. The findings of this study are relevant to fishery managers in updating current data collection protocols to alleviate data issues caused by bycatch loss, to conservation biologists in quantifying bycatch risks for susceptible seabird populations, and in aiding the design and evaluation of bycatch mitigation measures.
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Bethoney, N. David, Kevin D. E. Stokesbury, and Steven X. Cadrin. "Environmental links to alosine at-sea distribution and bycatch in the Northwest Atlantic midwater trawl fishery." ICES Journal of Marine Science 71, no. 5 (February 24, 2013): 1246–55. http://dx.doi.org/10.1093/icesjms/fst013.
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Abstract The bycatch of river herring (Alosa pseudoharengus and A. aestivalis) and American shad (A. sapidissima) by midwater trawl vessels targeting Atlantic herring (Clupea harengus) and Atlantic mackerel (Scomber scombrus) has become a possible threat to their conservation. Most bycatch occurs during winter when the regional distributions of these five species overlap. The life histories and habits of these species suggest that there are times and areas during winter where overlap is low and bycatch could be reduced. This study identified environmental conditions associated with the presence of river herring and American shad during winter in the US Mid-Atlantic area by testing the hypothesis that fish were detected in an equal proportion to the amount of samples taken within an environmental condition. River herring were associated with colder temperatures and relatively shallow depths, while American shad appeared to be associated with a broader habitat. To determine whether these associations could be used to reduce bycatch, the proportion of effort and catch of target and bycatch species under the conditions associated with bycatch species presence was quantified in a fishery-dependent dataset. Targeting Atlantic mackerel in waters with surface temperatures above 6°C appeared to be the most effective advice for reducing river herring bycatch.
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Hamid, Abdul, and Syamsul Kamri. "KEANEKARAGAMAN JENIS IKAN HASIL TANGKAPAN SAMPINGAN (BYCATCH) PERIKANAN RAJUNGAN DI TELUK LASONGKO DAN KENDARI SULAWESI TENGGARA." Marine Fisheries : Journal of Marine Fisheries Technology and Management 10, no. 2 (November 11, 2019): 215–24. http://dx.doi.org/10.29244/jmf.v10i2.30855.
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Information regarding the diversity of bycatch from blue swimming crab fishing operations is important in ecosystem-based management and assessment for Marine Stewardship Council (MSC) certification of crab fisheries in Southeast Sulawesi and Indonesia. However, data limitation becomes major challenges. This study aims to specify the types of bycatch caught from blue swimming crab fishing in Lasongko and Kendari Bay Southeast Sulawesi. This research was conducted in March to September 2019. Data was collected from trap and bottom gillnet fishing by using a purposive sampling method on a monthly basis. Bycatch was categorized into two groups, namely economically valuable and discarded, according to the local fishers’ perception. Information was presented both spatially and temporally. The results show that bycatch consists of 66 species including 41 economically valuable and 26 discarded species. Indices of diversity, evenness and dominance of fish were also discussed to describe the ecological conditions. Accordingly, this bycatch composition is able to support the management and assessment of MSC certification of crab fisheries in Southeast Sulawesi.
Keywords: bycatch, fish diversity, blue swimming crab fisheries, Southeast Sulawesi.
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Fox, CH, C. Robertson, PD O’Hara, R. Tadey, and KH Morgan. "Spatial assessment of albatrosses, commercial fisheries, and bycatch incidents on Canada’s Pacific coast." Marine Ecology Progress Series 672 (August 19, 2021): 205–22. http://dx.doi.org/10.3354/meps13783.
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Fisheries bycatch mortality poses a primary threat to the majority of the world’s 22 albatross species, 15 of which are at risk of extinction. Although quantitative estimates of albatross bycatch are often unavailable due to a relative or total absence of monitoring, spatial overlap between fisheries and albatrosses is often used to estimate the extent of interaction, a proxy for exposure to bycatch, and to inform avoidance and mitigation actions. Using comprehensive records of commercial demersal longline and trap fishing and survey information for albatrosses (black-footed albatross Phoebastria nigripes, Laysan albatross P. immutabilis, short-tailed albatross P. albatrus), the extent of spatial potential interaction was estimated in Canada’s Pacific coast waters and examined across breeding and non-breeding seasons. The distributions of albatrosses and longline and trap fisheries were found to substantially overlap, with potential interaction hotspots concentrated along the continental shelf break. Trap fisheries reported 1 albatross bycatch incident, suggesting that these fisheries are responsible for negligible albatross mortalities. In contrast, >80% of recorded albatross bycatch incidents occurred within 10 km of albatross-longline fisheries hotspot locations, providing evidence that longline-albatross potential interaction hotspots represent actual areas of elevated bycatch mortality risk. Indicative of potential conservation concern, 60% of short-tailed albatross sightings occurred within 10 km, and 93% within 30 km, of longline-albatross potential interaction hotspots. By contributing knowledge regarding albatross-fisheries interactions, in addition to undertaking the first evaluation of albatross-fisheries hotspots with recorded bycatch incidents on Canada’s Pacific coast, this study represents a step towards enhancing albatross conservation through bycatch avoidance and mitigation.
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Byrd, Barbie L., Lisa R. Goshe, Trip Kolkmeyer, and Aleta A. Hohn. "Sea Turtle Bycatch in the Large-Mesh Gillnet Flounder Fishery in Carteret County, North Carolina, USA, June-November 2009." Journal of North Carolina Academy of Science 132, no. 1-2 (March 1, 2016): 10–24. http://dx.doi.org/10.7572/jncas-15-00007.1.
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Abstract Sea turtle bycatch has been documented in the large-mesh gillnet fishery that targets flounder in estuarine waters of North Carolina (NC). However, only portions of the fishery operated under Endangered Species Act Incidental Take Permits and had regular observer coverage to determine the occurrence and extent of sea turtle bycatch. From June through November 2009, an Alternative Platform Observer Program (APOP) was initiated in southeastern Carteret County, NC, to document turtle entanglements. Observers covered 1.6% of the total number of large-mesh gillnet trips reported (1.1% of landings) and documented turtle bycatch (n = 22) on 36% of the observed trips (12 of 33). Most turtles were recovered alive (n = 15), and all interactions occurred in June, July, and August. Bycaught sea turtle species included 12 greens (Chelonia mydas), 5 Kemp’s ridleys (Lepidochelys kempii), and 5 loggerheads (Caretta caretta). Hauls with bycaught turtles in June had a significantly greater mean string length than those without bycatch (P = 0.02), but despite the institution of regulations limiting string length, no difference was found in mean string length overall before (June) and after (July-November) regulations went into effect. Documented turtle bycatch in this area supports the need for observer coverage across the entire spatio-temporal scope of the fishery at levels necessary for robust bycatch estimates. Representative observer data across longer time series can inform managers where and when bycatch risks are greatest and help in developing mitigation measures that decrease bycatch risk while reducing negative economic impacts on the fishers.
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Spencer, Paul D., Thomas K. Wilderbuer, and Chang Ik Zhang. "A mixed-species yield model for eastern Bering Sea shelf flatfish fisheries." Canadian Journal of Fisheries and Aquatic Sciences 59, no. 2 (February 1, 2002): 291–302. http://dx.doi.org/10.1139/f02-012.
Full textAbstract:
A variety of eastern Bering Sea (EBS) flatfish including yellowfin sole (Limanda aspera), rock sole (Lepidopsetta bilineata), flathead sole (Hippoglossoides elassodon), and Alaska plaice (Pleuronectes quadrituberculatus), co-occur in various degrees in EBS trawl fisheries, impeding attempts to obtain single-species management targets. A further complication is the bycatch of Pacific halibut (Hippoglossus stenolepis); halibut bycatch limits, rather than single-species catch quotas, have been the primary factor regulating EBS flatfish harvest in recent years. To examine bycatch interactions among the EBS flatfish listed above, an equilibrium mixed-species multifishery model was developed. Equilibrium yield curves, scaled by recent average recruitment, are flat topped or asymptotically increasing, reflecting low fishing selectivity during the first several years of life and low growth relative to natural mortality. A linear programming analysis indicated that relaxation of the halibut bycatch constraint at the optimal solution of catch by fishery would produce approximately 20 times more flatfish yield than a similar relaxation of any flatfish catch quota. A strategy for establishing halibut bycatch limits that considers the foregone revenue in the halibut and flatfish trawl fisheries reveals how the choice of halibut bycatch limit is affected by the management goal for the flatfish complex.
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Cortés, Federico, and Juan A. Waessle. "Hotspots for porbeagle shark (Lamna nasus) bycatch in the southwestern Atlantic (51°S–57°S)." Canadian Journal of Fisheries and Aquatic Sciences 74, no. 7 (July 2017): 1100–1110. http://dx.doi.org/10.1139/cjfas-2016-0114.
Full textAbstract:
Fisheries bycatch can severely affect the population status of species with low resilience such as sharks. Bycatch monitoring is an important issue for the development of conservation and management plans for these species. The main objectives of this study were to quantify and model the spatiotemporal trend of bycatch for porbeagle shark (Lamna nasus) in the Argentinean surimi trawl fleet to identify hotspots in the southwestern Atlantic Ocean. Using onboard observer data, we have demonstrated that L. nasus was usually caught as bycatch by the surimi trawl fleet operating in the southern limits of the southwestern Atlantic (51°S–57°S), representing an important part of the reported catch for the Atlantic Ocean. Delta and Tweedie models indicated that bycatch had a relatively stable trend, was concentrated in a limited region of the study area, and was associated with spatiotemporal, operational, environmental, and prey availability variables. The model with the best predictive capability used for the spatial delineation of hotspots for L. nasus bycatch showed that the areas located south of 54°12′S and over the continental shelf-break were critical for the porbeagle conservation and management strategies in the southwestern Atlantic Ocean.
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Gillespie, Alexander. "Wasting the Oceans: Searching for Principles to Control Bycatch in International Law." International Journal of Marine and Coastal Law 17, no. 2 (2002): 161–93. http://dx.doi.org/10.1163/157180802x00017.
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AbstractThe bycatch of species when fishing is now an international problem, which can drive species to the brink of extinction. This article examines some of the ways in which the various management regimes can confront this problem. These include defining the target species more accurately and modifying harvesting technology where necessary. If incidental species are still captured, other strategies include the release of bycaught species alive (when practical), the strict enforcement of direct quotas on bycatch take, coupled with incentives or disincentives to confront bycatch. The idea that bycatch may not be landed and profited from has an obvious attraction when dealing with species already the subject of separate conservation measures. However, to discard them completely is wasteful. Where bycatch species are not the subject of conservation regimes, their utilisation should be considered, although it is important that this does not result in perverse incentives.
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Miller, T. J., and J. R. Skalski. "Estimation of seabird bycatch for North Pacific longline vessels using design- and model-based methods." Canadian Journal of Fisheries and Aquatic Sciences 63, no. 8 (August 1, 2006): 1878–89. http://dx.doi.org/10.1139/f06-075.
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Bycatch estimation for sensitive species is becoming increasingly important with the shift toward an ecosystem-based approach to fisheries management. Incidental mortalities for various seabird species occur on longline vessels throughout the world, including those in the North Pacific groundfish fleet. We present an approach to seabird bycatch estimation for North Pacific longline vessels using observer-collected data. Observers collect enormous amounts of data through a complex sampling design, but some information deficiencies preclude bycatch estimation using only probability sampling. Our approach combines probability sampling with model-dependent techniques to overcome these information deficiencies. The resulting bycatch estimator reflects the observer sampling design as closely as possible and minimizes reliance on untested model assumptions. We apply our estimator to black-footed albatross (Phoebastria nigripes) bycatch as an example and compare yearly estimates to those previously published. We also suggest changes in data collection that would further reduce dependence on model assumptions.
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Maeda, Saki, Kenji Sakurai, Tomonari Akamatsu, Ayaka Matsuda, Orio Yamamura, Mari Kobayashi, and Takashi Fritz Matsuishi. "Foraging activity of harbour porpoises around a bottom-gillnet in a coastal fishing ground, under the risk of bycatch." PLOS ONE 16, no. 2 (February 11, 2021): e0246838. http://dx.doi.org/10.1371/journal.pone.0246838.
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Bycatch of harbour porpoises (Phocoena phocoena) by gillnets is a recognised threat to populations. To develop effective mitigation measures, understanding the mechanics of bycatch is essential. Previous studies in experimental conditions suggested foraging activity is an important factor influencing porpoises’ reaction to gillnets. We acoustically observed the behaviour of wild harbour porpoises around a bottom-gillnet set-up in a commercial fishing ground, especially foraging activity. Passive acoustic event recorders (A-tags) were fixed to the ends of the gillnet, and recorded for 1 392 hours. Although harbour porpoises frequently and repeatedly appeared around the net each day, incidental bycatch occurred only three times during the observations. The stomach contents of two individuals contained mainlyAmmodytessp., which were observable around the bottom-gillnet but not targeted by the fishery. A total of 276 foraging incidents were acoustically detected, and 78.2% of the foraging activity was in the bottom layer (deeper than 25 m). Porpoises appeared around the net with more frequency on the day of a bycatch incident than on the days without bycatch. These results suggest that the harbour porpoises appeared around the bottom-gillnet to forage on fish distributed in the fishing ground, but not captured by this bottom-gillnet. Thus, porpoises face the risk of becoming entangled when foraging near a gillnet, with the probability of bycatch simply increasing with the length of time spent near the net. Bycatch mitigation measures are discussed.
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Nurazizah, Harnum, Mirza Dikari Kusrini, and Ani Mardiastuti. "Bycatch of Amboina Box Turtle (<i>Cuora amboinensis</i>) by Fishermen in Rawa Aopa, Southeast Sulawesi." Journal of Tropical Biodiversity and Biotechnology 7, no. 2 (July 22, 2022): 72113. http://dx.doi.org/10.22146/jtbb.72113.
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Rawa Aopa is a permanent swamp ecosystem that serves as one of the suitable habitats for amboina box turtles (Cuora amboinensis). Some of the area is part of a national park (Rawa Aopa Watumohai National Park) and is designated as a traditional zone for fishing activities, where local fishermen sometimes reported accidental catch C. amboinensis in their fishing gear. The aims of this study were to record the existence of C. amboinensis bycatch, size and age structure of bycatch, characteristic of fishing activity, and to discuss the conservation implication of bycatch. The number of bycatch was recorded by direct observation of 7 selected fishermen in 14 days. The C. amboinensis caught accidentally were measured and weighed. A total of 38 individuals of C. amboinensis were accidentally caught by fishermen during the study, having a size ranged of 7.4 to 18.5 cm (juveniles, young adults, and old adults; no hatchling), and weighed 248 to 996 g. Based on sex, there was no significant difference between morphological size of male and female, although bycatch for females (59%) tend to be slightly higher than males (41%). Most of fishermen lives in Pewutaa Village and used bubu traps to catch fishes. C. amboinensis are the most common bycatch compared to other species. In order to minimize the impact of bycatch of the C. amboinensis by fishermen, we need to ensure that the turtle that accidentally trapped in the fishermen’s fishing gear would be released unharmedly to their habitat.
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Dagorn, Laurent, John D. Filmalter, Fabien Forget, Monin Justin Amandè, Martin A. Hall, Peter Williams, Hilario Murua, Javier Ariz, Pierre Chavance, and Nicolas Bez. "Targeting bigger schools can reduce ecosystem impacts of fisheries." Canadian Journal of Fisheries and Aquatic Sciences 69, no. 9 (September 2012): 1463–67. http://dx.doi.org/10.1139/f2012-089.
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Sustainability of living resource exploitation relies on an ecosystem management approach. Within tropical tuna purse seine fisheries using fish aggregating devices (FADs), such an approach incorporates the reduction of bycatch, in particular vulnerable species such as elasmobranchs. The levels of total bycatch (in mass) from fishing operations using FADs is known to be five times higher than when tuna are caught in free-swimming schools. We intend to find practical solutions to reduce bycatch in FAD sets through the investigation of the relationships between the ratio of bycatch to target catch across different set size classes in all oceans. Ratios were always highest when catches were small, with the smallest class of catches responsible for the highest total portion of bycatch (23%–43%) while only contributing negligibly to the total target catch (3%–10%). Reducing the number of fishing sets (a part of the total effort) while maintaining the same total yield could contribute to a substantial reduction in the impacts of human activities.
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Pratama, Andika Resa, Abdul Hamid, Syamsul Kamri, and Rahmad Sofyan Patadjai. "Diversity of Crustaceans Bycatch of Blue Swimming Crab (Portunus pelagicus) Fisheries of Landed in Leppe village, Soropia District, Konawe Regency." Journal of Tropical Fisheries Management 6, no. 2 (December 16, 2022): 95–102. http://dx.doi.org/10.29244/jppt.v6i2.43801.
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This research was aiming of find out the diversity of crustaceans bycatch of blue swimming crab (Portunus pelagicus) fisheries of moon period based. The method used was a survey method and sampling of crustacean bycatch was carried out during the period of bright moon (11-15 moon nights) and dark moon (27-1 moon nights). The results showed that there were 20 species of crustacean bycatch found during the study in which 17 species were found during the bright moon and 16 species were found during the dark moon. Thalamita danae species had the highest abundance during the dark and the bright moon period. The number of the male crustaceans bycatch was higher than the females for both bright and dark moon periods.Diversity index crustacean bycatch in both periods (brigh tand dark) ranged from 0.83 to 0.85. The evennes index and dominance index inthe bright and dark moon are the same (0.69 and 0.22, respectively).
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Mauliddin, Muhamad, Romie Jhonnerie, and Nofrizal Nofrizal. "Pengurangan Hasil Tangkapan Pada Alat Tangkap Togok dengan Menggunakan BRD (Bycatch Reduction Device) Tipe Rope BRD di Kuala Tungkal, Provinsi Jambi." Dinamika Lingkungan Indonesia 9, no. 2 (July 31, 2022): 113. http://dx.doi.org/10.31258/dli.9.2.p.113-117.
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Togok is a fishing gear in the form of a conical net body whose arms are on two poles and the success of catching it relies on currents, togok fishing gear is used to catch Rebon shrimp (Acetes japonicas) but in its operation, many catches are found bycatch. The high bycatch will have an impact on capture sustainable fisheries, one of the efforts to reduce bycatch is by using BRD (Bycatch Reduction Devices), the use of BRD has been widely carried out on trawl fishing gear but on togok fishing gear, it has never been done. This study aimed for knowing the reduction in catches of main catch, bycatch, and discard the togok fishing gear that has been installed with rope BRD and knows the reduction in catches of shrimp and fish species. This study uses experimental fishing, namely by carrying out direct fishing operations with local fishermen for 20 days of catch. The reduction of togok catch using BRD type rope BRD in the main catch is 8.4%, in bycatch is 11.8% and discard is 17, 1% and the reduction in catch of shrimp species ranged from 8,4% - 13,5% and reduction in catch of fish species ranged from 10,9% - 22,6%.
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Bjorkland, Rhema, Daniel C. Dunn, Michelle McClure, Jason Jannot, Marlene A. Bellman, Mary Gleason, and Katja Schiffers. "Spatiotemporal patterns of rockfish bycatch in US west coast groundfish fisheries: opportunities for reducing incidental catch of depleted species." Canadian Journal of Fisheries and Aquatic Sciences 72, no. 12 (December 2015): 1835–46. http://dx.doi.org/10.1139/cjfas-2014-0242.
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Spatial and temporal management measures to reduce nontarget catch are important strategies for rebuilding overfished rockfish (Sebastes spp.) populations in the Northeast Pacific. We describe efforts to support reducing rockfish bycatch in central California trawl fisheries by testing the efficacy of move-on rules on catch data from 2002 to 2010. Move-on rules are regulations or guidelines that trigger the temporary closure of a fishery in a targeted area when a bycatch threshold is reached, without the closure of the entire fishery. Move-on rules based on spatiotemporal autocorrelation (clustering) were effective in reducing bycatch with modest impact on target catch, removing between 35% and 77% of future hauls with bycatch within a specified distance and time of a bycatch-containing haul, while foregoing target catch by an average of 12%. The spatial and temporal peak clustering scales show correlation with the level of schooling behavior by each species; however, the efficiency of the rules measured either in reduction in bycatch hauls or diminished target catch was not strongly affected by those aggregation behaviors. Our analysis provides information for fishers, such as those in the California Risk Pool, in the continuing development of responses that are more refined in both scale and impact.
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O'Keefe, Catherine E., Steven X. Cadrin, and Kevin D. E. Stokesbury. "Evaluating effectiveness of time/area closures, quotas/caps, and fleet communications to reduce fisheries bycatch." ICES Journal of Marine Science 71, no. 5 (May 12, 2013): 1286–97. http://dx.doi.org/10.1093/icesjms/fst063.
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Abstract Designing effective bycatch mitigation programmes requires an understanding of the life histories of target and non-target species, interactions of fish and fishing gear, effects of spatial and temporal shifts in fishing effort, socio-economic impacts to the fishery, and incentives of fishery participants. The effects of mitigation measures (including fishing gear modification, time/area closures, bycatch quotas and caps, incentive programs, and fleet communication programs) have been evaluated with respect to reducing bycatch and discards. Less attention has been focused on evaluating unanticipated results related to shifts in fishing effort, changes in the size of non-target species caught, reduced catch of target species, and economic viability to fishing fleets. Time/area closures, bycatch quotas/caps, and fleet communication programmes were evaluated against a set of criteria to assess overall effectiveness in reducing bycatch without causing unintended biological and socio-economic impacts. The results suggest that wide-ranging studies of species' life histories, potential changes in fleet behaviour, and individual incentives are important for developing and implementing mitigation programmes. Combining a suite of mitigation techniques has been successful in meeting biological and socio-economic fisheries goals. Additionally, collaborative programmes that utilize the skill sets of fishers, scientists, and managers have increased effectiveness in meeting bycatch reduction objectives.
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Bi, Rujia, Yan Jiao, Haakon Bakka, and Joan A. Browder. "Long-term climate ocean oscillations inform seabird bycatch from pelagic longline fishery." ICES Journal of Marine Science 77, no. 2 (January 14, 2020): 668–79. http://dx.doi.org/10.1093/icesjms/fsz255.
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Abstract Seabirds are facing increasing threats in both marine and terrestrial habitats, and many populations have experienced dramatic declines over past decades. Fisheries bycatch is the most pervasive at-sea threat and is of increasing concern in fisheries management and marine conservation. We predicted spatial and temporal heterogeneities of seabird bycatch probability in the US Atlantic pelagic longline fishery (PLL) through an interactive Barrier model based on observer data from the National Marine Fisheries Service Pelagic Observer Program. The Barrier model prevents bias caused by physical barriers such as coastlines by defining the spatial correlation function as a collection of paths between points and eliminating any paths across physical barriers. The integrated nested Laplace approximations methodology and stochastic partial differential equations approach were applied to fit the model, greatly reducing execution time. Seabird bycatch had a hotspot of high bycatch probability in the mid-Atlantic bight in most years, and the hotspot varied in presence and location yearly. The inter-annual variations in bycatch hotspot are correlated with Gulf Stream meanders. Special area and time fishing restrictions predicted by relationships with Gulf Stream positions might enable the US Atlantic PLL to avoid peak areas and periods of seabird bycatch and thereby support seabird conservation.
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Runnebaum, J., KR Tanaka, L. Guan, J. Cao, L. O’Brien, and Y. Chen. "Predicting bycatch hotspots based on suitable habitat derived from fishery-independent data." Marine Ecology Progress Series 641 (May 7, 2020): 159–75. http://dx.doi.org/10.3354/meps13302.
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Bycatch remains a global problem in managing sustainable fisheries. A critical aspect of management is understanding the timing and spatial extent of bycatch. Fisheries management often relies on observed bycatch data, which are not always available due to a lack of reporting or observer coverage. Alternatively, analyzing the overlap in suitable habitat for the target and non-target species can provide a spatial management tool to understand where bycatch interactions are likely to occur. Potential bycatch hotspots based on suitable habitat were predicted for cusk Brosme brosme incidentally caught in the Gulf of Maine American lobster Homarus americanus fishery. Data from multiple fisheries-independent surveys were combined in a delta-generalized linear mixed model to generate spatially explicit density estimates for use in an independent habitat suitability index. The habitat suitability indices for American lobster and cusk were then compared to predict potential bycatch hotspot locations. Suitable habitat for American lobster has increased between 1980 and 2013 while suitable habitat for cusk decreased throughout most of the Gulf of Maine, except for Georges Basin and the Great South Channel. The proportion of overlap in suitable habitat varied interannually but decreased slightly in the spring and remained relatively stable in the fall over the time series. As Gulf of Maine temperatures continue to increase, the interactions between American lobster and cusk are predicted to decline as cusk habitat continues to constrict. This framework can contribute to fisheries managers’ understanding of changes in habitat overlap as climate conditions continue to change and alter where bycatch interactions could occur.
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Jubinville, I., E. Lawler, S. Tattrie, NL Shackell, J. Mills Flemming, and B. Worm. "Distributions of threatened skates and commercial fisheries inform conservation hotspots." Marine Ecology Progress Series 679 (November 25, 2021): 1–18. http://dx.doi.org/10.3354/meps13938.
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Bycatch in commercial fisheries is a pressing conservation concern and has spurred global interest in adopting ecosystem-based management practices. To address such concerns, a thorough understanding of spatiotemporal relationships among bycatch species, their environment and fisheries is required. Here we used a generalized linear mixed model framework incorporating spatiotemporal random effects to model abundance patterns for 3 skate species caught as bycatch in commercial fisheries (thorny skate Amblyraja radiata, winter skate Leucoraja ocellata and smooth skate Malacoraja senta), as well as 10 target species on the Scotian Shelf, NW Atlantic. Spatiotemporal estimates of relative abundance for at-risk skates within the years 2005-2015 were modelled from research trawl survey data and overlaid with those for target species to identify hotspots of bycatch risk. In addition, abundance estimates for at-risk skates within the years 1975-1985, a period of higher stock abundance, were used to identify areas of previously important habitat. Historically, skate species densely occupied areas near Sable Island and Banquereau Banks, Georges Bank and the Bay of Fundy. Bycatch hotspots between at-risk skates and commercial targets were identified in regions across the Scotian Shelf. These hotspots were independently validated by predicting species presence from at-sea observer data that monitor skate bycatch directly. We discuss spatial relationships between target and bycatch species, highlighting limitations of at-sea observer programmes that this method helps to address. This framework can be applied more broadly to inform ecosystem management and priority areas for conservation or fisheries regulation.
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Cleasby, IR, LJ Wilson, R. Crawford, E. Owen, Y. Rouxel, and M. Bolton. "Assessing bycatch risk from gillnet fisheries for three species of diving seabird in the UK." Marine Ecology Progress Series 684 (February 17, 2022): 157–79. http://dx.doi.org/10.3354/meps13944.
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Incidental mortality (bycatch) in fisheries represents a threat to marine vertebrates. Research has predominantly focussed on bycatch in longline fisheries, but bycatch from gillnet fisheries is of increasing concern. To address this concern, we combined comprehensive biologging data sets and multiple sources of fishing effort data to assess the spatial overlap of 3 diving seabird species during the breeding season (common guillemot Uria aalge, razorbill Alca torda and European shag Phalacrocorax aristotelis) with UK gillnet fisheries. Species distribution models based on birds’ diving behaviour identified areas of elevated bycatch risk where high levels of diving activity and fishing effort coincided. In addition, we identified times of day and water depths where diving activity, and hence bycatch risk, may be concentrated. Bycatch risk hotspots for all 3 species were identified along the north-east coast of England. Risk hotspots were also identified along the Pembrokeshire coast for both auk species and along the Cornish coast for shag. Lack of fishing effort data for smaller vessels made it difficult to assess seabird-fishery overlap in Scottish waters. Across species, diving activity was lower at night. For razorbill and guillemot, dive depth tended to increase at sunrise and decrease after sunset. For shag, dive depth showed no diel pattern but was associated with water depth. Our findings should assist in targeting spatio-temporal measures and designing deterrent devices to reduce bycatch. However, scarcity of data on the behaviour of gillnet fishers at comparable spatio-temporal resolution as seabird movement data remains a constraint to fully understanding seabird-fisheries interactions.
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Mangel, Jeffrey C., Joanna Alfaro-Shigueto, Matthew J. Witt, David J. Hodgson, and Brendan J. Godley. "Using pingers to reduce bycatch of small cetaceans in Peru's small-scale driftnet fishery." Oryx 47, no. 4 (May 10, 2013): 595–606. http://dx.doi.org/10.1017/s0030605312000658.
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AbstractThere is growing awareness that small-scale fisheries may have large impacts on threatened marine fauna. Bycatch of small cetaceans by the Peruvian small-scale driftnet fleet results in the deaths of thousands of animals annually. We sought to assess the effectiveness of acoustic alarms (pingers) for reducing the incidental capture of dolphins and porpoises by this fleet. Forty-three experimental trips (156 fishing sets) and 47 control trips (195 fishing sets) out of Salaverry Port, northern Peru, were observed from April 2009 to August 2011. Twenty-two percent of control sets captured small cetaceans (67 individuals) and 16% of experimental sets had captures of small cetaceans (33 individuals). The bycatch rate of experimental sets was 0.50 individuals km−2h−1, whereas for control sets the rate was 0.80 individuals km−2h−1. This 37% reduction in bycatch rate suggests that pingers may be effective in reducing the bycatch of small cetaceans in this fishery. Catch rates of the fishery's target shark and ray species were unchanged. Given the vast size of this fishery and its current levels of bycatch of small cetaceans (> 10,000 individuals annually), even the modest declines in bycatch we observed could result in reductions in mortality of hundreds or thousands of small cetaceans per annum. Challenges, including increased costs, to large-scale utilization of pingers have yet to be overcome. The harpooning of dolphins for use as bait will also need to be addressed for further reductions in dolphin and porpoise bycatch and mortality to be achievable.
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Roe, John H., Stephen J. Morreale, Frank V. Paladino, George L. Shillinger, Scott R. Benson, Scott A. Eckert, Helen Bailey, et al. "Predicting bycatch hotspots for endangered leatherback turtles on longlines in the Pacific Ocean." Proceedings of the Royal Society B: Biological Sciences 281, no. 1777 (February 22, 2014): 20132559. http://dx.doi.org/10.1098/rspb.2013.2559.
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Fisheries bycatch is a critical source of mortality for rapidly declining populations of leatherback turtles, Dermochelys coriacea . We integrated use-intensity distributions for 135 satellite-tracked adult turtles with longline fishing effort to estimate predicted bycatch risk over space and time in the Pacific Ocean. Areas of predicted bycatch risk did not overlap for eastern and western Pacific nesting populations, warranting their consideration as distinct management units with respect to fisheries bycatch. For western Pacific nesting populations, we identified several areas of high risk in the north and central Pacific, but greatest risk was adjacent to primary nesting beaches in tropical seas of Indo-Pacific islands, largely confined to several exclusive economic zones under the jurisdiction of national authorities. For eastern Pacific nesting populations, we identified moderate risk associated with migrations to nesting beaches, but the greatest risk was in the South Pacific Gyre, a broad pelagic zone outside national waters where management is currently lacking and may prove difficult to implement. Efforts should focus on these predicted hotspots to develop more targeted management approaches to alleviate leatherback bycatch.
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Soykan, CU, JE Moore, R. Zydelis, LB Crowder, C. Safina, and RL Lewison. "Why study bycatch? An introduction to the Theme Section on fisheries bycatch." Endangered Species Research 5 (2008): 91–102. http://dx.doi.org/10.3354/esr00175.
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Dineshbabu, A. P., Sujitha Thomas, Josileen Jose, P. T. Sarada, Lakshmi Pillai, Rekha Devi Chakraborty, Gyanranjan Dash, et al. "Bycatch in Indian trawl fisheries and some suggestions for trawl bycatch mitigation." Current Science 123, no. 11 (December 10, 2022): 1372. http://dx.doi.org/10.18520/cs/v123/i11/1372-1380.
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