Dissertations / Theses: 'Fishery Biology'

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Bochenek, Eleanor A. "Virginia's pelagic recreational fishery: Biological, socioeconomic and fishery components." W&M ScholarWorks, 1989. https://scholarworks.wm.edu/etd/1539616572.

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Catch, effort, fleet size and boat owner expenditure data were collected on Virginia's recreational marlin/tuna fishery for the 1983-1985 seasons. Logbooks, dockside interviews and a telephone survey were evaluated to determine which method was the most efficient and effective for collecting and estimating catch and effort for Virginia's pelagic recreational fishery. In 1984, logbooks were used to collect catch and effort data and fishing effort was estimated using Bochenek's method. Very few fishermen returned their logbooks and as a result this data is probably less reliable than the data collected in other years. Due to the poor return of logbooks, this method should not be used to assess Virginia's marlin/tuna fishery. For the 1985 season, Figley's telephone survey (1984) was compared to the NMFS dockside interview technique for large pelagics. Both the telephone survey using Figley's technique (1984) and dockside interviews using Bochenek's method for calculating effort appear to provide similar estimates of projected total catch. However, the dockside method is very labor intensive, costly and fraught with problems in estimating fishing effort. Therefore, the telephone survey technique using Figley's method for estimating effort appears to be a better method for analyzing this fishery. If telephone interviewing will not work in an area and dockside sampling methods must be relied upon to study the pelagic fishery, Bochenek's method appears to produce a better estimate of fishing effort. Using Figley's (1984) mark-recapture technique, Virginia's pelagic recreational fleet was estimated at 455 and 774 vessels in 1983 and 1985, respectively. Boat owner expenditures for this fleet were estimated at &3,863,045 in 1983, \&4,057,020 in 1984 and &5,538,191 in 1985. Bluefin tuna were caught at SST ranging from 58-83 F but seem to prefer SST of 70 to 75 F. Yellowfin tuna were caught at SST ranging from 68-86 F with the majority landed at SST of 76-80 F. White marlin appear to prefer SST of 74 to 81 F.

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Dutney, Luke. "Reproductive Biology and Controlled Reproductive Development of Captive Cobia (Rachycentron canadum)." Thesis, Fisheries Research and Development Corporation, 2016. http://era.daf.qld.gov.au/id/eprint/8755/.

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Cobia aquaculture began in Australia in 2007; however, expansion of commercial production has been limited, due in part to low and inconsistent supply of seed stock for ongrowing. This study aimed to address the constraints of reproductive performance of cobia in captive conditions and investigate strategies to improve the efficiencies of broodstock management in commercial and research facilities. In a study evaluating the growth of three cohorts of captive reared cobia, to determine the existence and extent of sexually dimorphic growth, intersex development in cobia was identified and recorded for the first time. There was no sexually dimorphic growth in the first two cohorts of fish. In contrast, females from third cohort were significantly larger than males once mean body weight exceeded 2 kg. It is proposed that the observed variations in growth and gonad malformations observed in cohorts 1 and 2 were the result of exposure to endocrine disruptors, the type and source of which remains unknown. In order to quantify the ovarian development of cobia, there was a need to develop an accurate method of assessing and quantifying ovarian maturation in the presence of asynchronous development. A simple, commercially applicable methodology was devised that used the proportional distribution of different oocyte stages to describe the developmental state of the ovary. Two trials were conducted to examine the effect of repeated injections of luteinising hormone releasing hormone analogue (LHRHa) and human chorionic gonadotropin (hCG) on stimulating vitellogenesis, supporting ovarian maturation and levels of circulating 17βestradiol (E2). Ovarian development was highly variable within treatments and those fish that initiated vitellogenesis continued to develop regardless of treatment with exogenous hormones. There was no change in E2 concentrations as a result of LHRHa injections and limited evidence to suggest a change in plasma E2 in response to hCG injection. While iv hormonal therapy is effective in inducing spawning in cobia, the results suggest that hormone therapy is not an effective approach to initiating or supporting early stage ovarian development in cobia. Two cohorts of cobia broodstock were assessed to examine ovarian development and circulating E2 in response to photothermal manipulation. In each study, broodstock were subjected to either a temporally compressed regime or an ambient regime. In the first study ovarian development was generally limited, irrespective of the phototherm regime and there was no significant difference in development between treatments. At the completion of the second trial there was no significant difference in ovarian development between the compressed and ambient phototherm; however, fish in the compressed phototherm were found to develop earlier in the season than those in ambient conditions. Fish in the first trial showed sporadic development in which ovarian samples contained low numbers of late stage oocytes amongst a large percentage of previtellogenic oocytes, possibly due to exposure to endocrine disruption in the early life history of the cohort. Two cohorts of captive reared cobia were progressively examined as pre- and postpubescent fish to examine the suitability of identifying gender by analysing the androgen 11-ketotestosterone (11KT) in blood and fin clip samples. The gender of individual cobia could be identified by analysing plasma 11KT between the months of October and March, provided the mean population weight was 2 kg or above. The measurement of 11KT concentrations in fin clip samples did not provide an accurate indication of plasma 11KT and as such, was not suitable for predicting gender in cobia. Overall the relative cost, infrastructure and equipment required to conduct steroid analysis limits the application of this methodology in commercial cobia production in comparison to the traditional method of gonadal biopsy.ref:68ga4

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Hudson, A. V. "The biology of seabirds utilising fishery waste in Shetland." Thesis, University of Glasgow, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234853.

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Hancock, Andrew. "The biology and fishery of Roe's abalone Haliotis roei Gray in south-western Australia, with emphasis on the Perth fishery /." Connect to this title, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0068.

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Hancock, Andrew (Boze) T. "The biology and fishery of Roe's abalone Haliotis roei Gray in south-western Australia, with emphasis on the Perth fishery." University of Western Australia. School of Animal Biology, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0068.

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The Roe’s abalone (Haliotis roei) fishery near Perth, Western Australia, is uniquely accessible, and highly vulnerable to overexploitation. The sustainability of this intensively utilized fishery requires robust assessment. To facilitate an assessment, this research aimed to provide rigorous and detailed biological information with appropriate interpretation. Four critical aspects of the species’ biology and population dynamics were investigated: (1) the stock structure; (2) the recreational catch; (3) an appropriate growth curve and description of size at age; and (4) abundance measures against which to assess the impact of fishing mortality. Allozyme electrophoresis was used to investigate stock structure across the species’ distribution. Standardized variance in allelic frequencies between 10 sites in south-western Australia indicated high levels of gene flow across the 3000 km sampled (mean FST = 0.009). An isolation-by-distance was evident when pairwise measures of GST were related to geographic distance (r=0.45, P<0.001). The area of complete genetic mixing was estimated from samples within the Perth fishery to be less than the distance between the two nearest sites, or 13 km. Consequently, the Perth fishery comprises numerous discrete stocks, each requiring independent assessment. A possible mechanism for this population structure is the retention of larvae in the wind driven currents oscillating in the near-shore lagoons, with rare pulses of long distance dispersal via the southerly Leeuwin current, running further offshore. The presumed impact of intensive recreational fishing, combined with substantial commercial quotas for the Perth fishery, had led to tight restrictions on fishing effort, without any quantitative measure of the recreational catch. A stratified creel survey was adapted to estimate the effort, catch rate and mean weight of abalone harvested by the recreational sector. Catches were estimated for reef complexes, or stocks, of less than 10 nautical miles (18.5 km) of coast. Between 1997 and 2000 the recreational catch varied from 30 to 45 tonnes whole weight, approximately equivalent to the commercial quota of 36 tonnes. On average 88% of the recreational catch came from two stocks, while 98% of the commercial catch came from these two, and one additional, stocks. The incidental mortality from recreational fishing, measured as the number of abalone left dead on the reef as a proportion of the estimated catch, was approximately 7% and 20% at two sites surveyed. Spatial and temporal patterns of growth were examined on the west coast of Western Australia. Growth increments were measured for abalone larger than about 30 mm from tagging studies at five sites in the Perth fishery, a site at the northern extent of the species’ distribution and a site in the southwest. Mean annual growth increments of the 0+ year class were obtained by fitting components to length frequencies from five sites in the Perth fishery, and combined with growth increments from each Perth tag site for model fitting. A von Bertalanffy growth curve provided a slightly better fit to the tag data, but a Gompertz growth curve was a much better fit when the mean increment from the 0+ to 1+ cohort was included, with the inflection occurring at about 40 mm, the size at sexual maturity. There was no difference in annual growth between the two years studied. There was significant variation in growth between the reef platform and adjacent sub-tidal reef, but this variation was site specific and faster growth rates were not consistently associated with either habitat. There was no latitudinal trend in growth rate. Growth at the Perth sites was the fastest and similar at all five sites with growth increments greater in summer than in winter. Size and abundance of abalone were measured using fixed transects and quadrats. Abalone densities were highest on the outer edge of the platform, intermediate in the middle of the reef platform, and lowest on both the inner platform and the sub-tidal reef. The pattern of mean lengths of abalone was the inverse of the density. Mean length and abundance were driven by the presence of post-settlement juveniles on the outer and middle reef habitats. There was a high spatial variation in abundance, with densities varying between transects at the same site, but the trend between years for each transect at a site was not significantly different. Abalone abundances, by size class, were examined from sites sampled between 1996 and 2002. A low density of post-settlement juveniles at all sites in 1997 was reflected in low densities of the 1+ and 2+ year classes in subsequent years. Abalone abundances at an unfished site were steady over the seven years. Two sites were located within each of the main stocks utilised by the recreational fishery. Abundance was stable or increasing in one stock, corresponding to a stable total catch. In the second stock the total catch increased over time and abundances declined. Perth is the focus of the Roe’s abalone fishery, with recreational and commercial fishers take about equal shares of the annual catch. Stocks are highly subdivided, with most of this catch coming from only 3 stocks occupying about 20 nautical miles of coast. Growth rates were found to be lower than previous estimates, and more similar to other commercial species of abalone. All life history stages are highly habitat specific, particularly the recruits, and the distribution and abundance through time indicate that the main stocks are near, or slightly over, the limit of sustainable fishing.

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Hancock, Andrew T. "The biology and fishery of Roe's abalone Haliotis roei Gray in south-western Australia, with emphasis on the Perth fishery." Connect to this title online, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0068/.

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Raji, Aminu. "Studies on freshwater fishery of a city lake." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233768.

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Ghofar, Abdul. "Population biology and fishery of squid and cuttlefish in the Alas Strait, Indonesia." Thesis, Bangor University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330106.

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Ngoile, M. A. K. "Fishery biology of the squid Loligo forbesi Steenstrup (Cephalopoda: Loliginidae) in Scottish waters." Thesis, University of Aberdeen, 1987. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU010097.

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A total of 6512 specimens of Loligo forbesi Steenstrup (Cephalopoda : Loliginidae), obtained from Scottish fishing ports and research vessels during 1984/86, was used to investigate aspects of fishery biology of the species in Scottish waters. L. forbesi exhibits sexual dimorphism in size, males had a larger overall mean size (DML, weight) than females, and for each sex the mean size was larger in those from the north-eastern Atlantic than in those from the North Sea. In length-weight relationship, females had a higher regression slope than males and this relationship for squids from Rockall was significantly different to those from the North Sea. Multivariate analyses on measurements of body parts showed that Rockall squid, also, exhibited less variation in body form but distinct differences from those of the west coast and North Sea. Recruitment of L. forbesi occurred during April/May and November/December, the monthly growth rate after recruitment varied between 12.5 to 28.6mm DML/month for males and 12.5 to 17.5mm DML/month for females; for each sex the November/December cohort had lower growth rate. The logistic growth model best fitted the progression of modes of monthly length frequencies. Age determinations estimated from statolith markings varied from under 3 months for 30mm DML individual to 28 months for 571mm DML male individual. Sex ratio in L. forbesi varied significantly from 1:1 throughout the year with males exceeding females except during winter when the number of females may be equal to/or more than males. Mean size at maturity was 205mm DML for males and 192mm DML for females. Spawning occurred during December to March and the peak spawning period occurred in February throughout the study area. In this species, maturity coefficient and gonad-somatic index were the best indices for identification of spawning season. Fecundity is related to size and the average number of eggs per female was 6500.High proportions of specimens with 'empty' stomach were observed during the winter. The prey of L. forbesi was fish, crustaceans, molluscs and polychaetes in decreasing order of incidence. Identified fish prey were Argentina sphryaena, Trisopterus esmakii, Merlangius merlangus and Ammodytes sp.

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Lam, Yan-yan Vivian. "The shark fisheries of Southern China and the reproductive biology of the spadenose shark, Scoliodon laticaudus." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43278541.

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Trotta, Kristina Ann. "Socioeconomics of the Lionfish Derby Fishery." NSUWorks, 2014. http://nsuworks.nova.edu/occ_stuetd/21.

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Throughout the western North Atlantic Ocean, Caribbean Sea, and the Gulf of Mexico, invasive Indo-Pacific lionfish (Pterois volitans/miles) have established dense populations, greatly impacting their host environments. Lionfish tournaments have been an important tool for resource managers and other concerned stakeholders in suppressing local populations of lionfish. Tournaments can also bring economic benefits to the communities where they are held, despite this not being the primary purpose. Five derby events in Florida and the Bahamas were surveyed and 119 participants were interviewed on site, using a survey asking them to describe (1) the lionfish derby experience; (2) non-derby related lionfish removal effort; (3) derby expenditures; and (4) personal characteristics. Response rates of event participants were between 35% and 82%. Respondents spent an average of approximately $820 per person, potentially creating a net economic benefit to the communities where they were held. Total expenditures reported ranged from $5,000 to over $60,000 per tournament, with events drawing a high number of out of town participants reporting the highest amounts spent. Participants surveyed were largely males who resided in Florida and had a reported income of over $100,000 with 29% indicating an annual income of more than $200,000. In addition, lionfish tournaments have the effect of educating the public about the lionfish invasion, including greater targeting and consumption of lionfish, showing that tournaments are effective at their conservation mission as well as contributing to the economy of their host community.

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To, Wai-lun. "The biology, fishery of groupers (family: serranidae) in Hong Kong and adjacent waters, and implications for manangement." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42182566.

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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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Dudley, Sheldon Francis John. "Snoek Thyrsites atun in South African waters : aspects of its biology, distribution and fishery." Master's thesis, University of Cape Town, 1987. http://hdl.handle.net/11427/22189.

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Bibliography: pages 100-108.
The snoek Thyrsites atun is an important fish predator in the southern Benguela region. It is exploited by both a handline and a demersal fishery. A survey of the Cape line fishery revealed that snoek line fishing effort is changing from the traditional harbour-based line-boat to the nomadic ski-boat. It was widely claimed that snoek catches are declining and that migration patterns are changing. Snoek constitute a by-catch of the hake-directed demersal fishery but nevertheless are seasonally important. The principle prey of snoek caught by handline off the Cape Peninsula were anchovy and mantis shrimp. Snoek caught in midwater trawls offshore were feeding primarily on anchovy, with pilchard, euphausiids and amphipods also important. Snoek trawled demersally had a more diverse diet, dominated by redeye roundberring, lightfish, lanternfish, hake, buttersnoek and euphausiids. Snoek were caught in the demersal environment throughout daylight hours, but may come off the bottom at night. The small degree of overlap between the diet of snoek caught demersally offshore and that of snoek caught in the pelagic zone, both inshore and offshore, indicates that snoek do not seem to move extensively on a diurnal basis between the two zones. Over the period 1970 to 1985 availability of snoek to the handline fishery was strongly seasonal, with catches peaking from May to July, although the traditional winter snoek run is a declining phenomenon along the South African coast. At Dassen Island, for which catch data have only been available since 1981, peak months were from November to January. The snoek seems to move offshore from July and is trawled demersally until September. The presence of snoek larvae offshore between June and September indicates an offshore spawning migration. With the exception of the summer presence in the region of Dassen Island, snoek appear to be present in the southern Benguela region between April and September. Handline catches of snoek have declined markedly since 1978, but demersal catches have remained more stable.

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Tallack, Shelly M. L. "The biology and exploitation of three crab species in the Shetland Islands, Scotland : Cancer pagurus, Necora puber and Carcinus maenas." Thesis, Open University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272972.

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Ho, Chun-man Valerie. "Biology and fishery of the bartail flathead, Platycephalus indicus (Linnaeus, 1758), in the Northern South China Sea." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B36629108.

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au, andrew@wrlc com, and Andrew Charles Winzer. "The biology and prevalence of Cirolana hesperia and their effect on the Western Rocklobster Fishery." Murdoch University, 2007. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20090727.115745.

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The current study had two overriding and inter-related aims. The first was to describe the biology of C. hesperia the dominant scavenging subtidal cirolanid found in temperate waters off the Perth metropolitan coastline and thereby extend our knowledge and test several hypotheses regarding the biology of scavenging crustaceans in general. The second was to use the biological information generated to develop fishing practices that reduce the amount of bait used by trap based fisheries without reducing the overall catch. Fulfilling the latter aim has the potential to greatly reduce some of the deleterious effects of fishing practices around the world. A survey was designed to determine whether the anecdotal evidence that commercial rocklobster fishers believe sea lice have a negative impact on the ratio of bait used to rocklobster landed was widespread across the fishery and, if so, whether they associated particular factors with increases or decreases in lice numbers. The response rate of over 40% was high for a survey of this type and had similar return rates across all zones of the fishery. Such a high return rate, in addition to the responses confirms that commercial fishers, regardless of zone, consider that sea lice have adverse effects on the ratio of bait used to rocklobster landed. The findings of the survey allowed the following conclusions to be drawn and hypotheses developed. Commercial fishers believe particular temporal and spatial factors are associated with increased numbers of sea lice predating on rocklobster baits. For example, fishing in depth ranges of 20 - 30 fathoms (40 60 metres) and greater, fishing on a sand bottom, fishing during the months of November, December, March and April, fishing during the full and new moons and lastly during periods of weak current and high water temperature were all felt to increase the number of sea lice scavenging on baits. Laboratory growth trials demonstrated significant differences in the mean body lengths of starved and fed manca and adult C. hesperia after three and seven months, respectively. Despite these findings, starved adult C. hesperia continued to moult and grow after approximately 300 days of fasting. The relatively short period of time before differences in starved and fed manca C. hesperia growth parameters arose is probably due to early life stages of cirolanids being more reliant on regular food sources than their adult counterparts. An increase in water temperature from 16 ºC to 24 ºC resulted in no significant increase in mean body length of manca C. hesperia. However, the mean inter-moult period of fed manca housed at 24 ºC was significantly lower (25-50%) than both the fed treatment group housed at 16 ºC and the starved treatment group within the first two months of the trial. This reduction in mean inter-moult period is indicative of an animal which is growing quickly as a result of increased metabolic rate albeit at reduced increments. The 24 hour activity rhythms of C. hesperia in shallow waters in the metropolitan zone of the Western Rocklobster Fishery were determined in order to identify those factors which modulate the emergence and/or swimming activity of this dominant scavenger. It was concluded that the presence of a circadian rhythm of spontaneous nocturnal activity induced by the end of the diurnal period of photo-inhibition,regardless of tidal regime or lunar cycle, is evident in adult C. hesperia. In contrast, circa-tidal rhythms of emergence centered around spring tides were found to exist in juvenile C. hesperia with similar mean numbers trapped across all sampling times (see Chapter 3, tables 3.4-3.8) with the exception of high water spring tides (HWS), which resulted in significantly greater mean numbers. It was concluded that mature cirolanids found off the Western Australian coastline adopt a strictly nocturnal and facultative necrophage mode of existence despite carrion generally being regarded as a much less crucial food resource in relatively shallow, productive, inshore waters. However, juvenile cirolanids found off the Western Australian coastline were recognised as relying on a more opportunistic scavenger mode of existence being active during both day and night. This perpetual foraging strategy employed in cirolanids at manca and juvenile stages is possibly due to the lack of the well developed chemosensory and or olfactory capabilities found in their adult stages. In addition to this reduced foraging efficiency, a smaller gut size combined with higher metabolic rates and lower assimilation efficiencies ensures their ongoing search for sustenance. Analyses of the number of C. hesperia collected during three years of trapping in C zone of the Western Rocklobster Fishery clearly demonstrated that the numbers of cirolanids caught in rocklobster pots were significantly affected by bottom type, moon phase and depth. With respect to bottom type, the greatest numbers of C. hesperia were trapped in rocklobster pots deployed on weed/rock and sand bottoms while significantly lower numbers of C. hesperia were trapped on rock or weed bottoms. In regards to moon phase, rocklobster pots deployed during the new and last quarter of the moon phase trapped significantly greater numbers of both C. hesperia and the Western Rocklobster, P. cygnus than those deployed during the full and first quarter phases. Rocklobster pots containing lice traps deployed in depths ranging from 10-19 and 20-29 fathoms (20-39 and 40-59 metres respectively) caught significantly greater numbers of C. hesperia and P. cygnus than pots deployed in the 1-19 metre depth range. Lastly, the catchability of both C. hesperia and P. cygnus was greatest when either Australian salmon or blue mackerel was deployed in pots indicating these scavengers do exercise a degree of selectivity with respect to particular bait types. Whilst ovigerous C. hesperia were present in each month of the year, peaks in their abundance and/or catchability occurred at the height of summer (January to March). These peaks in mpm, i.e. morphological parturial moult stage, C. hesperia were then followed by corresponding peaks in recruitment from April to June. I hypothesise that peaks in the reproductive intensity of C. hesperia can be attributed to peaks in water temperature and also the seasonal influx of carrion due to both recreational and commercial charter fishing and the commencement of the rocklobster season all occurring predominately within a similar time frame, i.e. the warmer months. The current study has clearly demonstrated that a plethora of factors attract high numbers of both C. hesperia and P. cygnus. Thus, it is apparent that those practices employed by commercial fishers to land the greatest number of P. cygnus will also attract significant numbers of C. hesperia to rocklobster baits. Irrespective of key factors driving C. hesperia abundance, the high market price received for P. cygnus in conjunction with the relatively low price payed for bait, ensures fishers will continue to deploy rocklobster pots in the manner which maximises their landings. Thus for a reduction in bait usage to offer significant economic savings to the industry, different methods of bait deployment that do not result in a decrease in the catch of P. cygnus must be developed. A series of baitsaver trials were conducted in order to determine whether baitsavers deployed containing reduced quantities of bait would catch the same numbers of rocklobster as conventional pots using the typical amounts of bait employed in the fishery. During the start of the season the majority of fishers concentrate their efforts in shallow waters and employ predominantly one day soaks as they target rocklobster migrating from the shallows to offshore habitats (whites phase November to February). In the later parts of the season (reds phase March to June) fishing effort becomes less concentrated as some fishers continue to fish the inshore grounds whilst others move out into deeper waters. The season long trial demonstrated that packing large quantities of bait in both baitboxes in the pot (traditional method) caught significantly more rocklobster than pots using a baitsaver in one bait box while the other bait box was packed in traditional fashion (combined method) during the first two months of the whites phase. However, during the remainder of the season there was no significant difference in catches between the two methods. Thus, the season-long trial found that the use of traditional methods of bait deployment in the first two months of the season in conjunction with the combined method of bait deployment from January until the end of the commercial season has the potential to save inshore and offshore based fishers $34,000 and $36,000 each year.

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18

Winzer, Andrew Charles. "The biology and prevalence of Cirolana hesperia and their effect on the Western Rocklobster Fishery." Thesis, Winzer, Andrew Charles (2007) The biology and prevalence of Cirolana hesperia and their effect on the Western Rocklobster Fishery. PhD thesis, Murdoch University, 2007. https://researchrepository.murdoch.edu.au/id/eprint/678/.

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Abstract:

The current study had two overriding and inter-related aims. The first was to describe the biology of C. hesperia the dominant scavenging subtidal cirolanid found in temperate waters off the Perth metropolitan coastline and thereby extend our knowledge and test several hypotheses regarding the biology of scavenging crustaceans in general. The second was to use the biological information generated to develop fishing practices that reduce the amount of bait used by trap based fisheries without reducing the overall catch. Fulfilling the latter aim has the potential to greatly reduce some of the deleterious effects of fishing practices around the world. A survey was designed to determine whether the anecdotal evidence that commercial rocklobster fishers believe sea lice have a negative impact on the ratio of bait used to rocklobster landed was widespread across the fishery and, if so, whether they associated particular factors with increases or decreases in lice numbers. The response rate of over 40% was high for a survey of this type and had similar return rates across all zones of the fishery. Such a high return rate, in addition to the responses confirms that commercial fishers, regardless of zone, consider that sea lice have adverse effects on the ratio of bait used to rocklobster landed. The findings of the survey allowed the following conclusions to be drawn and hypotheses developed. Commercial fishers believe particular temporal and spatial factors are associated with increased numbers of sea lice predating on rocklobster baits. For example, fishing in depth ranges of 20 - 30 fathoms (40 – 60 metres) and greater, fishing on a sand bottom, fishing during the months of November, December, March and April, fishing during the full and new moons and lastly during periods of weak current and high water temperature were all felt to increase the number of sea lice scavenging on baits. Laboratory growth trials demonstrated significant differences in the mean body lengths of starved and fed manca and adult C. hesperia after three and seven months, respectively. Despite these findings, starved adult C. hesperia continued to moult and grow after approximately 300 days of fasting. The relatively short period of time before differences in starved and fed manca C. hesperia growth parameters arose is probably due to early life stages of cirolanids being more reliant on regular food sources than their adult counterparts. An increase in water temperature from 16 ºC to 24 ºC resulted in no significant increase in mean body length of manca C. hesperia. However, the mean inter-moult period of fed manca housed at 24 ºC was significantly lower (25-50%) than both the fed treatment group housed at 16 ºC and the starved treatment group within the first two months of the trial. This reduction in mean inter-moult period is indicative of an animal which is growing quickly as a result of increased metabolic rate albeit at reduced increments. The 24 hour activity rhythms of C. hesperia in shallow waters in the metropolitan zone of the Western Rocklobster Fishery were determined in order to identify those factors which modulate the emergence and/or swimming activity of this dominant scavenger. It was concluded that the presence of a circadian rhythm of spontaneous nocturnal activity induced by the end of the diurnal period of photo-inhibition,regardless of tidal regime or lunar cycle, is evident in adult C. hesperia. In contrast, circa-tidal rhythms of emergence centered around spring tides were found to exist in juvenile C. hesperia with similar mean numbers trapped across all sampling times (see Chapter 3, tables 3.4-3.8) with the exception of high water spring tides (HWS), which resulted in significantly greater mean numbers. It was concluded that mature cirolanids found off the Western Australian coastline adopt a strictly nocturnal and facultative necrophage mode of existence despite carrion generally being regarded as a much less crucial food resource in relatively shallow, productive, inshore waters. However, juvenile cirolanids found off the Western Australian coastline were recognised as relying on a more opportunistic scavenger mode of existence being active during both day and night. This perpetual foraging strategy employed in cirolanids at manca and juvenile stages is possibly due to the lack of the well developed chemosensory and or olfactory capabilities found in their adult stages. In addition to this reduced foraging efficiency, a smaller gut size combined with higher metabolic rates and lower assimilation efficiencies ensures their ongoing search for sustenance. Analyses of the number of C. hesperia collected during three years of trapping in C zone of the Western Rocklobster Fishery clearly demonstrated that the numbers of cirolanids caught in rocklobster pots were significantly affected by bottom type, moon phase and depth. With respect to bottom type, the greatest numbers of C. hesperia were trapped in rocklobster pots deployed on weed/rock and sand bottoms while significantly lower numbers of C. hesperia were trapped on rock or weed bottoms. In regards to moon phase, rocklobster pots deployed during the new and last quarter of the moon phase trapped significantly greater numbers of both C. hesperia and the Western Rocklobster, P. cygnus than those deployed during the full and first quarter phases. Rocklobster pots containing lice traps deployed in depths ranging from 10-19 and 20-29 fathoms (20-39 and 40-59 metres respectively) caught significantly greater numbers of C. hesperia and P. cygnus than pots deployed in the 1-19 metre depth range. Lastly, the catchability of both C. hesperia and P. cygnus was greatest when either Australian salmon or blue mackerel was deployed in pots indicating these scavengers do exercise a degree of selectivity with respect to particular bait types. Whilst ovigerous C. hesperia were present in each month of the year, peaks in their abundance and/or catchability occurred at the height of summer (January to March). These peaks in mpm, i.e. morphological parturial moult stage, C. hesperia were then followed by corresponding peaks in recruitment from April to June. I hypothesise that peaks in the reproductive intensity of C. hesperia can be attributed to peaks in water temperature and also the seasonal influx of carrion due to both recreational and commercial charter fishing and the commencement of the rocklobster season all occurring predominately within a similar time frame, i.e. the warmer months. The current study has clearly demonstrated that a plethora of factors attract high numbers of both C. hesperia and P. cygnus. Thus, it is apparent that those practices employed by commercial fishers to land the greatest number of P. cygnus will also attract significant numbers of C. hesperia to rocklobster baits. Irrespective of key factors driving C. hesperia abundance, the high market price received for P. cygnus in conjunction with the relatively low price payed for bait, ensures fishers will continue to deploy rocklobster pots in the manner which maximises their landings. Thus for a reduction in bait usage to offer significant economic savings to the industry, different methods of bait deployment that do not result in a decrease in the catch of P. cygnus must be developed. A series of baitsaver trials were conducted in order to determine whether baitsavers deployed containing reduced quantities of bait would catch the same numbers of rocklobster as conventional pots using the typical amounts of bait employed in the fishery. During the start of the season the majority of fishers concentrate their efforts in shallow waters and employ predominantly one day soaks as they target rocklobster migrating from the shallows to offshore habitats (whites phase – November to February). In the later parts of the season (reds phase – March to June) fishing effort becomes less concentrated as some fishers continue to fish the inshore grounds whilst others move out into deeper waters. The season long trial demonstrated that packing large quantities of bait in both baitboxes in the pot (traditional method) caught significantly more rocklobster than pots using a baitsaver in one bait box while the other bait box was packed in traditional fashion (combined method) during the first two months of the whites phase. However, during the remainder of the season there was no significant difference in catches between the two methods. Thus, the season-long trial found that the use of traditional methods of bait deployment in the first two months of the season in conjunction with the combined method of bait deployment from January until the end of the commercial season has the potential to save inshore and offshore based fishers $34,000 and $36,000 each year.

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19

Winzer, Andrew Charles. "The biology and prevalence of Cirolana hesperia and their effect on the Western Rocklobster Fishery." Winzer, Andrew Charles (2007) The biology and prevalence of Cirolana hesperia and their effect on the Western Rocklobster Fishery. PhD thesis, Murdoch University, 2007. http://researchrepository.murdoch.edu.au/678/.

Full text

Abstract:

The current study had two overriding and inter-related aims. The first was to describe the biology of C. hesperia the dominant scavenging subtidal cirolanid found in temperate waters off the Perth metropolitan coastline and thereby extend our knowledge and test several hypotheses regarding the biology of scavenging crustaceans in general. The second was to use the biological information generated to develop fishing practices that reduce the amount of bait used by trap based fisheries without reducing the overall catch. Fulfilling the latter aim has the potential to greatly reduce some of the deleterious effects of fishing practices around the world. A survey was designed to determine whether the anecdotal evidence that commercial rocklobster fishers believe sea lice have a negative impact on the ratio of bait used to rocklobster landed was widespread across the fishery and, if so, whether they associated particular factors with increases or decreases in lice numbers. The response rate of over 40% was high for a survey of this type and had similar return rates across all zones of the fishery. Such a high return rate, in addition to the responses confirms that commercial fishers, regardless of zone, consider that sea lice have adverse effects on the ratio of bait used to rocklobster landed. The findings of the survey allowed the following conclusions to be drawn and hypotheses developed. Commercial fishers believe particular temporal and spatial factors are associated with increased numbers of sea lice predating on rocklobster baits. For example, fishing in depth ranges of 20 - 30 fathoms (40 – 60 metres) and greater, fishing on a sand bottom, fishing during the months of November, December, March and April, fishing during the full and new moons and lastly during periods of weak current and high water temperature were all felt to increase the number of sea lice scavenging on baits. Laboratory growth trials demonstrated significant differences in the mean body lengths of starved and fed manca and adult C. hesperia after three and seven months, respectively. Despite these findings, starved adult C. hesperia continued to moult and grow after approximately 300 days of fasting. The relatively short period of time before differences in starved and fed manca C. hesperia growth parameters arose is probably due to early life stages of cirolanids being more reliant on regular food sources than their adult counterparts. An increase in water temperature from 16 ºC to 24 ºC resulted in no significant increase in mean body length of manca C. hesperia. However, the mean inter-moult period of fed manca housed at 24 ºC was significantly lower (25-50%) than both the fed treatment group housed at 16 ºC and the starved treatment group within the first two months of the trial. This reduction in mean inter-moult period is indicative of an animal which is growing quickly as a result of increased metabolic rate albeit at reduced increments. The 24 hour activity rhythms of C. hesperia in shallow waters in the metropolitan zone of the Western Rocklobster Fishery were determined in order to identify those factors which modulate the emergence and/or swimming activity of this dominant scavenger. It was concluded that the presence of a circadian rhythm of spontaneous nocturnal activity induced by the end of the diurnal period of photo-inhibition,regardless of tidal regime or lunar cycle, is evident in adult C. hesperia. In contrast, circa-tidal rhythms of emergence centered around spring tides were found to exist in juvenile C. hesperia with similar mean numbers trapped across all sampling times (see Chapter 3, tables 3.4-3.8) with the exception of high water spring tides (HWS), which resulted in significantly greater mean numbers. It was concluded that mature cirolanids found off the Western Australian coastline adopt a strictly nocturnal and facultative necrophage mode of existence despite carrion generally being regarded as a much less crucial food resource in relatively shallow, productive, inshore waters. However, juvenile cirolanids found off the Western Australian coastline were recognised as relying on a more opportunistic scavenger mode of existence being active during both day and night. This perpetual foraging strategy employed in cirolanids at manca and juvenile stages is possibly due to the lack of the well developed chemosensory and or olfactory capabilities found in their adult stages. In addition to this reduced foraging efficiency, a smaller gut size combined with higher metabolic rates and lower assimilation efficiencies ensures their ongoing search for sustenance. Analyses of the number of C. hesperia collected during three years of trapping in C zone of the Western Rocklobster Fishery clearly demonstrated that the numbers of cirolanids caught in rocklobster pots were significantly affected by bottom type, moon phase and depth. With respect to bottom type, the greatest numbers of C. hesperia were trapped in rocklobster pots deployed on weed/rock and sand bottoms while significantly lower numbers of C. hesperia were trapped on rock or weed bottoms. In regards to moon phase, rocklobster pots deployed during the new and last quarter of the moon phase trapped significantly greater numbers of both C. hesperia and the Western Rocklobster, P. cygnus than those deployed during the full and first quarter phases. Rocklobster pots containing lice traps deployed in depths ranging from 10-19 and 20-29 fathoms (20-39 and 40-59 metres respectively) caught significantly greater numbers of C. hesperia and P. cygnus than pots deployed in the 1-19 metre depth range. Lastly, the catchability of both C. hesperia and P. cygnus was greatest when either Australian salmon or blue mackerel was deployed in pots indicating these scavengers do exercise a degree of selectivity with respect to particular bait types. Whilst ovigerous C. hesperia were present in each month of the year, peaks in their abundance and/or catchability occurred at the height of summer (January to March). These peaks in mpm, i.e. morphological parturial moult stage, C. hesperia were then followed by corresponding peaks in recruitment from April to June. I hypothesise that peaks in the reproductive intensity of C. hesperia can be attributed to peaks in water temperature and also the seasonal influx of carrion due to both recreational and commercial charter fishing and the commencement of the rocklobster season all occurring predominately within a similar time frame, i.e. the warmer months. The current study has clearly demonstrated that a plethora of factors attract high numbers of both C. hesperia and P. cygnus. Thus, it is apparent that those practices employed by commercial fishers to land the greatest number of P. cygnus will also attract significant numbers of C. hesperia to rocklobster baits. Irrespective of key factors driving C. hesperia abundance, the high market price received for P. cygnus in conjunction with the relatively low price payed for bait, ensures fishers will continue to deploy rocklobster pots in the manner which maximises their landings. Thus for a reduction in bait usage to offer significant economic savings to the industry, different methods of bait deployment that do not result in a decrease in the catch of P. cygnus must be developed. A series of baitsaver trials were conducted in order to determine whether baitsavers deployed containing reduced quantities of bait would catch the same numbers of rocklobster as conventional pots using the typical amounts of bait employed in the fishery. During the start of the season the majority of fishers concentrate their efforts in shallow waters and employ predominantly one day soaks as they target rocklobster migrating from the shallows to offshore habitats (whites phase – November to February). In the later parts of the season (reds phase – March to June) fishing effort becomes less concentrated as some fishers continue to fish the inshore grounds whilst others move out into deeper waters. The season long trial demonstrated that packing large quantities of bait in both baitboxes in the pot (traditional method) caught significantly more rocklobster than pots using a baitsaver in one bait box while the other bait box was packed in traditional fashion (combined method) during the first two months of the whites phase. However, during the remainder of the season there was no significant difference in catches between the two methods. Thus, the season-long trial found that the use of traditional methods of bait deployment in the first two months of the season in conjunction with the combined method of bait deployment from January until the end of the commercial season has the potential to save inshore and offshore based fishers $34,000 and $36,000 each year.

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20

Engström, Henri. "Effects of Great Cormorant Predation on Fish Populations and Fishery." Doctoral thesis, Uppsala University, Department of Evolutionary Biology, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-1506.

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The strong increase in number of Great cormorants Phalacrocorax carbo in Sweden in recent years has led to conflicts - particularly with fishery. This thesis focuses on the possible effects of cormorant predation on fish populations. In total, data from 15 lakes in South Sweden were included in this study while most studies were carried out in Lake Ymsen. The results suggest that the impact of cormorant predation on natural fish populations was small, and I observed no decline in fish mass after cormorants established. Cormorant predation on eel was difficult to evaluate because of several confounding factors.

Ruffe, roach and perch were the most important prey species to the cormorants and most fish taken were small. Cormorants do not seem to catch species and sizes in proportion to their occurrence in the fish community.

Total fish removal by cormorants varied considerably among lakes (0.2-15.0 kg/ha) and cormorant population sizes at the different lakes were significantly positively correlated with fishery catches, which in turn was significantly positively correlated with total phosphorous levels. Thus, cormorant densities in lakes, and perhaps elsewhere, seem to be governed chiefly by fish densities. The fact that cormorant predation appears not to reduce fish densities suggest cormorants to be regulated by other means than prey depletion. The mechanism behind population regulation could be a behavioural response of fish, making fish more difficult to catch for the cormorants.

In recent years, cormorant populations have been subjected to intensive legal and illegal actions with the aim to reduce cormorant numbers. However, the actions currently carried are well below the efforts needed to limit population sizes. To conclude, cormorants appear to compete little with fishery, with regards to free-living fish. The main problem is that cormorants sometimes damage and take away fish in fishing gears.

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21

Armitage, Thomas M. "A bioeconomic model of the middle Atlantic surf clam (Spisula solidissima) fishery." W&M ScholarWorks, 1985. https://scholarworks.wm.edu/etd/1539616551.

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A bioeconomic simulation model of the middle Atlantic surf clam (Spisula solidissima) fishery has been developed from a survey of biological and econometric relationships. While identifying the biological input parameters available in the literature, the economic submodel of the fishery has been developed with price and landings time series data, and with data obtained through the use of survey questionnaires and interviews with surf clam fishermen and processors. Alternative management scenarios in the fishery have been evaluated from industry costs in both the harvesting and processing sectors and analysis of the demand for raw product confronting surf clam fishermen. Multiple regression analysis of time series data indicates that surf clam ex-vessel prices may be negatively related to surf clam landings whereas hard clam prices are positively related to ex-vessel ocean quahog prices and ex-vessel oyster prices. The strength of this relationship confirms the status of ocean quahogs as very close substitutes for surf clams. The results of case studies using the model suggest that the Mid-Atlantic Fishery Management Council has followed a prudent course of action in managing the surf clam fishery. The model also projects that, (1) larger yield quotas may be possible in the immediate future without jeopardizing surf clam population stability, (2) overcapitalization in the fishery appears to remain a problem, and (3) the economic outlook for the operators of small vessels remains relatively bleak.

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22

Horton, Christopher Michael 1973. "Possible limiting factors for a sustainable crappie fishery in the Salt River chain of reservoirs, Arizona." Thesis, The University of Arizona, 1997. http://hdl.handle.net/10150/278628.

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The dynamics of crappie populations in southwestern reservoirs are not well documented. In order for managers to enhance a crappie fishery, they need to understand the factors that control populations. I examined potential limiting factors for black crappie in 4 sequential reservoirs on the Salt River, Arizona. Only in Roosevelt Reservoir, the uppermost reservoir, were crappie relatively abundant. I identified 3 possible limiting factors. Apache, Canyon, and Saguaro reservoirs lacked sufficient spawning substrates. All 4 reservoirs lacked sufficient cover. Finally, the lower 3 reservoirs are less productive during the fall according to chlorophyll a levels than Roosevelt Reservoir. Low productivity may have resulted in fewer zooplankton and possibly a limited forage base for juvenile crappie. Options such as spawning platforms, artificial cover, fertilization, and stocking are discussed as ways to improve the crappie fishery in these reservoirs.

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23

To, Wai-lun, and 杜偉倫. "The biology, fishery of groupers (family: serranidae) in Hong Kong andadjacent waters, and implications for manangement." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42182566.

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24

Luyeye, Nkosi. "Studies of biology ecology and school behaviour of Sardinella in the Angolan fishery by Nkosi Luyeye." Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/6123.

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Bibliography: leaves 115-134.
This study investigated the biological characteristics (linked with daynight and migration aspects) of the stock, the behavioural patterns of sardinella spp (schoolbehaviour and dynamics) that may lead to under-estimation as well as bias. Biological and acoustic data collected during 22 pelagic surveys (1985-1999), as well as schooling records of three cruises (1996-1998), were used to study the biology, distribution, behaviour of the school dynamics of sardinella.

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25

Kaltayev, Arman O. "The Human Factor in Size Selectivity in the Sea Scallop, Placopecten magellanicus Fishery." W&M ScholarWorks, 2000. https://scholarworks.wm.edu/etd/1539617755.

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26

Dannewitz, Johan. "Genetic and Ecological Consequences of Fish Releases : With Focus on Supportive Breeding of Brown Trout Salmo trutta and Translocation of European Eel Anguilla anguilla." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3764.

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27

Jayakody, D. S. "Fishery, population dynamics and breeding biology of Panulirus homarus (L.) on the south coast of Sri Lanka." Thesis, University of Stirling, 1991. http://hdl.handle.net/1893/26681.

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This study is aimed to provide an understanding of the spiny lobster fishery of the south coast of Sri Lanka. Most of the spiny lobster fisheries of the world are subjected to heavy exploitation due to the increasing demand. The use of hazardous fishing methods however is known to cause serious problems in the developing countries, including Sri Lanka where considerable percentage of berried females and under sized lobsters are caught each year. The fishery for spiny lobster in the coastal waters of the south coast is carried out by non-mechanized out-rigger small canoes with trammel nets, bottom set gill nets and lobster rings. Around 200mt of lobsters is caught each year in the study area by a fishing fleet of 315 crafts. Around 80% of the lobster production consisted of Panulirus homarus. Lobsters were found to occur all year round, but the fishery is restricted to the non-monsoon period (August-March) due to operational difficulties. The analysis of catch and effort statistics indicated a maximum sustainable yield of 190-200 mt and an optimal daily effort of 300 crafts. The length-based analysis indicated that the resource is over exploited and a reduction in effort by about 20.5% is necessary to put the fishery back to an equilibrium level. Experimental fishing tests revealed that the lobster rings cause the least damage to the population, while the trammel net was the most harmful by including 77% of sub-legal lobsters in catches. This study indicated the possibility of having two spawning and recruitment pulses separated by an interval of 4-5 months. Fecundity estimates ranged between 116,000 - 601,000. Nearly two-third of the total egg production was contributed by lobsters of 60-79mm carapace length range. The fishery is reproductively supported by 3-4 year lobsters. This resource in the study area appears to be overfished with respect to its reproductive potential. The use of trammel nets and free access to the fishery are the two main points which should be carefully controlled. The fishery should be managed by using less harmful fishing gear (eg. lobster rings) and by introducing a proper licensing system to control fishermen entering into the fishery.

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28

Ho, Chun-man Valerie, and 何臻敏. "Biology and fishery of the bartail flathead, Platycephalus indicus (Linnaeus, 1758), in the Northern South China Sea." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B36629108.

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29

Muir, Samantha Deborah. "The biology of razor clams ('Ensis' spp.) and their emergent fishery on the west coast of Scotland." Thesis, University of London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406101.

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30

Maldeniya, Rekha Rasanjani Perera. "Small scale multispecies demersal fishery off Negombo, Sri Lanka : a study of their biology and socio-economics." Thesis, University of Stirling, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365093.

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31

Glass, James Patrick. "The fishery and biology of the rock lobster Jasus tristani at the Tristan da Cunha Islands group." Thesis, Cape Peninsula University of Technology, 2014. http://hdl.handle.net/20.500.11838/2033.

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Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Oceanography in the Faculty of Applied Sciences at the Cape Peninsula University of Technology 2014
The Tristan lobster Jasus tristani is distributed among several isolated islands and submerged seamounts in the South East Atlantic Ocean. This species occurs only at the Tristan da Cunha group, a British Overseas Territory and the World’s most remote inhabited island, and in international waters at Vema Seamount 1680 km ENE of Tristan. All these populations are exploited commercially. The catch, processing and export of J. tristani is the most important economic activity for the inhabitants of Tristan da Cunha, providing the livelihood of many families and accounting for approximately 80% of the Island’s revenue. Sustainable harvesting of this valuable resource requires accurate long-term data on catch and effort, as well as information on the most important biological parameters such as growth, recruitment, moulting and reproductive cycles. This information is critical for robust assessments and management strategies. This thesis describes the history of the lobster fishery at the Tristan da Cunha island group, reporting on catches and trends in Catch Per Unit Effort between 1967 and 2010. A total of 247,014 lobster samples, both sexes combined, was sampled for size composition and sex ratios, as well as 1,526 lobsters for length/weight relationships, between 1997 and 2010. This confirms earlier findings that females have broader and heavier tails than males for the same carapace length (CL). Results show that males dominate catches at all islands, and their average size was larger than that of females (83.5 ± 14.46 versus 73.4 ± 8.64 mm CL, respectively). Inter-island differences in lobster population structure appear to be caused by differences of food availability as well as in density-dependent growth and survival of young lobsters. The largest lobsters were found at Gough Island (87.2 ± 15.13 mm CL), and the smallest at Inaccessible island (73.2 ± 11.39 mm). Tristan was the next largest to Gough Island (84.0 ± 12.56 mm) followed by Nightingale island (78.2 ± 11.33 mm). Lobsters caught inshore were larger than those caught offshore, although this may be related in part to differences in catches between fishing gear types. This study showed that fecundity increases in a linear manner with CL, and although larger lobsters clearly produce more eggs than smaller ones, the gain in fecundity is not as great as in some lobster species where fecundity is more closely associated with weight. The study showed no significant differences in egg size between islands, or between large and small females at one island. The egg production per gram of body weight and mean egg diameter both seem to be less than reported in an earlier study in the 1990s. While it seems likely that this is due to differences in the way in which samples were collected (with only stage 2 ova collected and measured in this study), the possibility of a decline in fecundity needs to be investigated further. A range of management measures have been developed over the history of the fishery, and important current measures include an annual total allowable catch (TAC) for each island, minimum size limits, and a closed season timed to protect egg-bearing females. The fishery has recently been awarded certification by the Marine Stewardship Council. The study has confirmed that current conversion factors are broadly correct and that different size limits established for each island are justified. Concern is raised, however, by the fall in catch per unit effort and the mean size of lobsters at the three northern islands over the past 7 years. These trends will need to be closely monitored. There are still many uncertainties over key parameters such as growth and recruitment and the intention is to increase the knowledge base and our understanding of the dynamics of the lobster stock. A research plan has been developed, so that progress can be monitored through the gradual implementation of scientifically defendable fisheries management procedures and increased research and monitoring capacity.

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32

Hill, Jacqueline Mary. "Structure and flow of carbon and nitrogen to the western Irish Sea Nephrops norvegicus fishery : a stable isotope approach." Thesis, Queen Mary, University of London, 2008. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1483.

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Stable isotope analysis was used to describe the structure and flow of organic matter (carbon and nitrogen) from primary production in the water column to the benthos, and into secondary production that supports a fishery for the lobster Nephrops norvegicus in the western Irish Sea. There was strong seasonal variation in the carbon and nitrogen stable isotopes of organic matter associatedw ith the seasonalc ycle of primary production in the surfacew aters. The seasonal isotope signal was used to trace the flow of organic matter from primary production through herbivorous zooplankton to the carnivorous pelagic larvae of Nephrops norvegicus.T he production of larvae represented0 .2 % of spring bloom production. Stable isotope analysis of organic matter throughout the water column was used to track the vertical flux of primary production from the surface to the benthos. The isotope signal was also used to quantify the input of carbon to the benthos, estimated to be 41 % of spring bloom primary production. The carbon input to the benthos supported a simple food chain of three higher trophic levels (TL2 - TL4). Nephrops norvegicus was positioned at TU where it accounted for 96 % of the total biomass at that level. The input of carbon to the benthos was equal to the removal of carbon from the benthos by the Nephrops norvegicus fishery assuming a transfer efficiency of 16 % between each trophic level. Climate warming has caused a decline in primary production in some marine systems. Should similar impacts occur in the western Irish Sea,t he subsequendt ecline in the flux of carbon to the benthos will result in a shortfall in the supply of carbon needed to support the current catch rate of the Nephrops norvegicus fishery.

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33

Mugabe, Eulália D. "Aspects of the biology, ecology and fishery of the beaked clam Eumarcia paupercula (Holten, 1802), in Maputo Bay." Doctoral thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/23051.

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Clam populations globally have declined, or been depleted, with one of the major causes being uncontrolled human exploitation. This thesis investigates the population structure, growth, reproduction and exploitation of the beaked clam Eumarcia paupercula in Maputo Bay. The substantial commercial harvesting of this clam may lead to overexploitation of the resource. In this regard, some fundamental knowledge is necessary for the management of future exploitation. The data collection was based on an 18-months (November 2012 - April 2014) sampling for population structure across a tidal flat. The growth analysis was performed on FiSAT II, using mark-recapture experiments and length-frequency data. Monthly reproduction analysis was based on the fluctuation of body weight and gonad smear analysis. Furthermore, interviews were used to ascertain the importance of the resources for collectors and estimate landings of E. paupercula. The von Bertalanffy growth function and length-frequency analysis revealed that E. paupercula has a fast growth rate and a short life span. Eumarcia paupercula is a year-round spawner with higher peaks in the summer; recruitment follows a similar pattern, occurring over the year and after the spawning peaks. The clam collectors, the majority of whom are women, have experienced an increase in the effort required to collect clams, resulting in a decline of catches over the season. This study highlights that temporal population dynamics are influenced by collection and reproductive patterns, and that single environmental parameters do not explain the patterns of growth, reproductive cycles and spatial distribution. Findings of this study have relevance and application for the livelihood of the collectors, as well as the sustainability of the Eumarcia paupercula stock, by providing a basis for fishery governance. While recommendations are presented for the management of E. paupercula collection, the Ministry of Fishery in Mozambique also has to consider collecting data on bivalves, as they are an important source of income for artisanal fishers. Future research should include monitoring of a less exploited population, so as to understand better how collection impacts on the population dynamics of E. paupercula. Furthermore, laboratory studies of the larval cycle are necessary to gain thorough understanding of the species life cycle.

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Supriatna, Asep K. "Optimal harvesting theory for predator-prey metapopulations /." Title page, contents and abstract only, 1998. http://web4.library.adelaide.edu.au/theses/09PH/09phs959.pdf.

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35

Ngugi, Charles Chege. "The biology of naturalized rainbow trout, Oncorhynchus mykiss (Walbaum), in Kenya cold water streams and implications for future management." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ62456.pdf.

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Hearn, Alex. "The biology and fishery of the velvet swimming crab, Necora puber (L.) (Brachyura, Portunidae) in the Orkney Islands, UK." Thesis, Heriot-Watt University, 2001. http://hdl.handle.net/10399/1107.

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Lam, Yan-yan Vivian, and 林因恩. "The shark fisheries of Southern China and the reproductive biology of the spadenose shark, Scoliodon laticaudus." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43278541.

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Nthimo, Mokitinyane Francis. "The biology of commercially important fish species and a preliminary assessment of the fisheries potential of Katse Dam, Lesotho." Thesis, Rhodes University, 2000. http://hdl.handle.net/10962/d1005081.

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The construction of the Katse dam was completed in 1996. The dam started filling in 1995 and reached full capacity in early 1998. It forms part of Phase 1A of the Lesotho Highlands Water Project (LHWP). The main aim of the project is to provide revenue to Lesotho, by transferring water from the catchment of the Senqu (Orange) River in Lesotho to South Africa’s major industrial and population centres. During the implementation of the project, an estimated 130 people were displaced. However, the most serious impact has been the loss of the traditional way of life in the form of arable and grazing land as a consequence of inundation. One of the obligations of the project is to ensure that the standard of living of those affected by the project is not impaired. The Lesotho Highlands Development Authority identified a number of rural development projects, which included fisheries development. This study is an integral part of fisheries development in Lesotho. The aim of this study was to gain an understanding of the biology and the demographics of the fish species in the lake. This information would serve as the basis for the development of a management plan for the sustainable utilisation of the fisheries resources. To achieve this aim, the following specific objectives were addressed: 1. Investigation of the biology of the three principal species. 2. Description of the key population parameters (growth, mortality & recruitment). 3. Investigation of the distribution and relative abundance of the three species. The three principal species in the Katse dam are rainbow trout, Oncorhynchus mykiss, and the two cyprinids, Barbus aeneus and Labeo capensis. Sectioned otoliths were used to age O. mykiss while both otoliths and scales were used to age B. aeneus and L. capensis. Marginal zone analysis revealed that slow growth was experienced in winter for the three species. The maximum-recorded age for both B. aeneus and L. capensis was 12 years while O. mykiss reached 4 years. There was no significant difference in growth rates of the different sexes and growth was best described by the 3 parameter Von-Bertalanfy growth model as Lt = 603[1-e⁻°·¹⁵⁽t ⁺ °·°³⁾] for B. aeneus, Lt = 526[1-e⁻°·²¹⁽t ⁺ °·⁹⁾] for O. mykiss and Lt = 521[1-e⁻°·¹⁷⁽t ⁺ °·²¹⁾] for L.capensis. Male and female O. mykiss attained 50% sexual maturity (Lm₅₀) at 235 and 275mm FL, respectively. There was no difference in Lm₅₀ for male and female B. aeneus and L. capensis. B. aeneus reached sexual maturity at 285mm FL while L. capensis reached sexual maturity at 244mm. Both cyprinid species spawned in summer (November to January) while O. mykiss spawned in winter (May to August). The mean total mortality rate (Z) estimated from catch curves and Butterworth et al (1989) equation was 0.72 yr⁻¹ for B. aeneus, 0.62 yr⁻¹ for L. capensis and 1.32 yr⁻¹ for O. mykiss. The estimate of natural mortality was 0.41 yr⁻¹ for both B. aeneus and L. capensis and 0.81yr⁻¹ for O. mykiss.

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Tuuli, Cynthia Darta. "The croaker fishery and dried swimbladder trade in Hong Kong, and the reproductive biology of the greyfin croaker, Pennahia Anea." Thesis, Click to view the E-thesis via HKUTO, 2010. http://sunzi.lib.hku.hk/hkuto/record/B43778367.

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Rook, Benjamin J. "Cisco recruitment dynamics in Lake Superior during 1978-2007 /." Link to full text, 2009. http://epapers.uwsp.edu/thesis/2009/Rook.pdf.

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Thesis (M.S.)--University of Wisconsin--Stevens Point, 2009.
Submitted in partial fulfillment of the requirements of the degree Master of Science in Natural Resources (Fisheries), College of Natural Resources. Includes bibliographical references (leaves 176-190).

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Fernandez, John. "Analysis of increases in fishing power in the western rock lobster (Panulirus cygnus) fishery." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 1999. https://ro.ecu.edu.au/theses/1227.

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The western rock lobster, Panulirus cygnus, fishery represents a significant commercial asset to Western Australia, and it is therefore important that appropriate strategies are developed to effectively manage it. Because the fishery has a very high level of exploitation, researchers and managers rely significantly on annual stock assessments which are based on catch and effort data. This study will identify and assess the effects that changes in fishing power factors (e.g. advances in fish-finding technology) have had on estimates of catch and effort. The fishing power increases can be used to adjust nominal fishing effort to produce a time series of standardised effort which can then be used to reassess stock abundance measures, particularly of the breeding stock. The study will utilise the theory and techniques of regression and generalised linear modelling. A comparison of the normal and gamma distributions as the specified probability distribution in the model will be made .

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Laurenson, Chevonne Hazel. "Aspects of the biology and fishery for monkfish Lophius piscatorius Linnaeus 1758 in waters around the Shetland Isles, Northeastern Atlantic." Thesis, University of Aberdeen, 2003. http://www.ices.dk/products/CMdocs/2001/J/J2701.pdf.

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Huveneers, Charlie. "The ecology and biology of wobbegong sharks (Genus Orectolobus) in relation to the commercial fishery in New South Wales, Australia." Thesis, Electronic version, 2007. http://hdl.handle.net/1959.14/198.

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Thesis by publication.
Thesis (PhD)--Macquarie University (Division of Environmental & Life Sciences, Graduate School of the Environment), 2007.
Bibliography: p. 267-303.
General introduction -- Redescription of two species of wobbegongs (Chondrichthyes: Orectolobidae) with elevation of Orectolobus halei Whitley 1940 to species level -- Using recreational scuba-divers to survey the relative abundance and distribution of wobbegong sharks (Family: Orectolobidae) in New South Wales, Australia -- Observations of localised movements and residence time of wobbegong sharks (Orectolobus halei) at Fish Rock, New South Wales, Australia -- Length-frequency distribution, length-length, mass-mass and mass-length relationships of wobbegong sharks (Genus Orectolobus) commercially fished in New South Wales, Australia -- Quantitative diet assessment of wobbegong sharks (Genus Orectolobus) in New South Wales, Australia -- Reproductive synchrony of three sympatric species of wobbegong shark (Genus Orectolobus) in New South Wales, Australia -- Age and growth of wobbegong sharks (Genus Orectolobus) in New South Wales, Australia.
In New South Wales, Australia, wobbegong sharks (Orectolobidae) have been commercially targetted by the Ocean Trap and Line Fishery since 1991. A catch decrease of ca. 50% in a decade lead to concern over the sustainability of the fishery and to wobbegongs being listed as vulnerable in NSW under the World Conservation Union Red List assessment. The aim of this research was to investigate wobbegong biology and ecology in relation to its fishery to provide essential data and information for sustainable management of the woggegong fishery. Biological data was obtained from 904 wobbegongs collected from commercial fishing boats, using setlines and lobset pots and by scuba diving. previously two species of wobbegongs were known to occur in NSW: the spotted wobbegong (Orectolobus maculatus) and the ornate wobbegong (O. ornatus). This study discovered a new species (O. halei) described as a subspecies by Whitley (1940), but which had been syonymised with O> ornatus due to a lack of taxonomic investigation.
Mode of access: World Wide Web.
307 p. ill., some col., maps

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Pulfrich, Andrea Christine. "Aspects of the biology of, and fishery for, the Hottentot, Pachymetopon blochii (Val.) (Sparidae), in the Western and Southwestern Cape." Master's thesis, University of Cape Town, 1987. http://hdl.handle.net/11427/21932.

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Data extracted from historic records have been used together with information collected during a survey of major fishing centres in the west and southwest Cape, from Port Nolloth to Struis Bay, to document the development of the handline fishery, with special reference to the fishery for hottentot Pachymetopon blochii (Val.). The fishing communities are described and social conditions are compared with those reported in earlier surveys. Changes in the fishing vessels and tackle used in the handline fishery are described and the economic status of the fishery evaluated. The distribution and availability of P. blochii are assessed in relation to the various tackle types and catch methods in different areas and the contribution by this species to the total annual linefish catch is estimated. Total fishing effort expended in the commercial linefishery is used to calculate catch-per-unit-effort indices for the hottentot fishery and the seasonal and long-term trends in these indices are evaluated in relation to past and present constraints on the marketing of this species.

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Smith, Craig Deon. "Population biology and ecology of octopuses in the Southwestern Cape : astudy towards the establishment of a small-scale octopus fishery." Master's thesis, University of Cape Town, 1999. http://hdl.handle.net/11427/22620.

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46

Srinoparatwatana, Chongdee. "Population biology of two key fish species and the dynamics and management of the trap fishery in Beung Borapet, Thailand." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2009. https://ro.ecu.edu.au/theses/2093.

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Inland water bodies provide important fisheries resources in Thailand and elsewhere in south-east Asia, yet there is limited information on the biology of important species and catch rates in fisheries, and limited assessment of management strategies such as Freshwater Protected Areas. This study has provided important information on aspects of the biology of knifefish (Notopterus notopterus) and catopra (Pristolepis fasciatus), two dominant freshwater fish species in Thailand, as well as catch and effort trends in the trap fishery and the influence of a Freshwater Protected Area (FPA) on fish communities in Beung Borapet, a large freshwater swamp and an international important wetland in Central Thailand (15ºN; 100ºE). Both N. notopterus and P. fasciatus were shown to be the most dominant species using traps in fisheries-independent (18.3 and 23.2%, respectively) and fisheries dependent (31.2 and 22.9%, respectively) studies, and were therefore shown to be important species in Beung Borapet. Female N. notopterus reached maturity at 178 mm TL, while female P. fasciatus reached maturity at about 70 mm TL. Both species spawned throughout most of the year, with peak spawning between June and August when rainfall peaked and water levels were rising for N. notopterus and between April and September when water temperature and daylight length were peaking for P. fasciatus. Furthermore, both species are multiple spawners, with the former exhibiting low batch fecundity (approximately 113 and 864 eggs) and the latter showing high batch fecundiy (approximately 10,000 and 62,000 eggs). The high batch fecundity and the daily spawning of P. fasciatus is would result in a high total fecundity for the species. The sex ratio of P. fasciatus exhibited a slight male bias in fish <100 mm, but this reverse to a clear female bias in larger fish. For both species, growth parameters could not be determined using either cohort analyses from length frequency data, or length-at age data from growth increments in hard structures such as scales and otoliths. The catch composition of the trap and gillnet fishery in Beung Borapet was dominated by five species, namely P. fasciatus, N. notopterus, Oreochromis niloticus, Cyclocheilichthys repasson and Cyclocheilichthys apogon. Traps tended to catch larger fish of more marketable size than gill nets, especially for N. notopterus and O. niloticus. The trap fishery yielded approximately 92 tonnes (2.9 kg/hectare) of fish per year, which was valued at nearly 3 Million Baht (~$US 80,000), which provided an average net income of 83,000 Baht (~$US 2,100) for a fulltime trap fisher in Beung Borapet. Spatial closure management is a strategy used throughout the world for protecting aquatic biodiversity and promoting fish production. The FPA in Beung Borapet contained lower overall densities and biomass of fish than the fished area, but there were inconsistent patterns among fish species. Some dominant species, such as Cyclocheilichthys enoplos and Amblyrhynchichthys truncatus, had higher densities, while others, such as P. fasciatus and O. niloticus, had lower densities in the FPA. Furthermore, larger sizes of only a few dominant species were observed in the protected zone, e.g. P. fasciatus and N. notopterus. The benefits of the FPA for fisheries enhancement and conservation of biodiversity appear to be limited due to observed illegal fishing activities in the zone as well as higher turbidity related to point-source impacts observed in other studies. Management of the conservation zone in the region requires a combination of top-down and bottom-up approaches and scientific information to improve the effectiveness of FPAs. Fisheries management needs to focus on both the resources and the stakeholders to minimize conflict among different stakeholders and inform them of conservation issues for their natural resources to promote their participation in the management strategies.

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McAuley, Rory B. "Investigation of the fishery biology and population status of the sandbar shark (Carcharhinus plumbeus, Nardo 1827) in Western Australian waters." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2007. https://ro.ecu.edu.au/theses/280.

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The sandbar shark (Carchrarhinus plumbeus) is a commercially important shark species to fisheries around the world but is known to be highly susceptible to over·fishing. During the late 1990s, changes in the targeting practices of Western Australian demersal gillnet fishing vessels, and an expansion of targeted demersal longlining in the north of the State, caused a rapid escalation in C. plumbeus catches. This study therefore aimed to collect the biological and fishery data necessary to assess the impacts of increasing exploitation of the species and to develop biologically appropriate techniques for assessing the sustainability of these fishery developments.

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Corrick, Corey Travis. "Spatial variation in fishery exploitation of mature female blue crabs (C. sapidus) in Chesapeake Bay." UNF Digital Commons, 2018. https://digitalcommons.unf.edu/etd/798.

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From 2008 to 2012, the total U.S. commercial landings of blue crabs (Callinectes sapidus Rathbun, 1896) averaged over 173 million lbs. Chesapeake Bay and its tributaries are important contributors to this fishery, providing greater than 30% of national commercial landings annually. In Chesapeake Bay, C. sapidus exhibits a complex life cycle in which mated females migrate to the saline waters of the Bay mouth to spawn. During migration, females can traverse multiple management jurisdictions, complicating effective management of this important fishery. Sustained declines in harvest have led to management strategies focused on protecting the female spawning stock in an attempt to enhance recruitment back into the Bay. This study presents the results of a broad scale mark-recapture study (n=7,072) in 11 Chesapeake Bay subestuaries and one coastal embayment, designed to track female migration and quantify spatial variation in exploitation rates of mature female blue crabs. Tagging was conducted in fall 2014 (September and October), when most females have matured and begin to migrate to the spawning grounds, and in summer 2015 (July), when additional females mature and migrate to the spawning grounds. Approximately 8.1% of tagged females were recaptured within one year of release. Overall, the exploitation rate of the 2015 blue crab spawning stock in Chesapeake Bay was 10.5%; however exploitation varied widely among systems (4.0-28.5%). This estimate is below both the management target and threshold exploitation rates and the population grew in subsequent years, suggesting recruitment overfishing of blue crabs was not occurring in Chesapeake Bay at this time.

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Dahle, Samuel Kirk. "Predicting the Growth Potential of a Shallow, Warm-Water Sport Fishery: A Spatially Explicit Bioenergetics Approach." DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/275.

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Capturing the range of fish consumption and growth potential of large, heterogeneous lentic systems can be challenging due to strong gradients in productivity, the diversity of habits types present, and in some cases, site-specific water quality issues. Cutler Reservoir (Utah, USA) displays a high degree of spatial and temporal variation in physical conditions and potential water quality limitations for fish, including high summertime water temperature and large, diel fluctuations in dissolved oxygen concentrations. The combination of bioenergetics modeling and GIS spatial analysis offers a promising interface for quantifying the fish consumptive and growth potential across a spatially and temporally heterogeneous system like Cutler Reservoir, as well as identifying the role of potential water quality impairment on fish population abundance and condition. Within a bioenergetics framework, we combined empirical field estimates of fish growth and diet composition with a novel use of Thermal Remote Imaging (TIR) as a measure of spatially explicit thermal regime across a very large spatial scale (9,601,200 m2). We used these data inputs and a Geographic Information System (GIS) to generate spatially explicit, high-resolution maps of the growth potential of the primary sport fishes of Cutler Reservoir across spring, summer, and autumn seasons. The predicted growth potential of these fishes varied widely according to spatial and temporal differences in temperature and food availability, acting in concert with species-specific physiological tolerances and habitat preferences. Walleye (Sander vitreus) and black crappie (Pomoxis nigromaculatus) experience high growth potential throughout much of the reservoir during spring and fall, but are constrained to small thermal refugia during the heat of the summer. In contrast, channel catfish (Ictalurus punctatus) growth potential is low during spring and fall, but peaks strongly during the warm summer period. The proportion of habitat suitable for each primary sport fish ranged from highs of > 90% for channel catfish for most of the summer season to lows < 5% for crappie in July. Our approach provides a useful tool for analyzing factors that control fish growth in complex water bodies such as Cutler Reservoir as well as identifying the role of water quality in structuring fish community composition.

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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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Dissertations / Theses on the topic 'Fishery Biology'

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