In the Eastern Tropical Pacific (ETP), the operation mode of purse-seine fishing can be divided into dolphin sets and non-dolphin sets. Dolphin sets can catch more yellowfin tuna, but cause a lot of dolphin deaths. On the contrary, non-dolphin sets can catch more skipjack tuna, but discard a lot of tuna. Therefore, the choice of the operation mode to the ETP purse-seine fishery is very influential. If the fishermen use more dolphin sets, they are able to catch high quantity and more valuable yellowfin tuna. Conversely, if the fishermen use more non-dolphin sets, they will not hurt dolphins. But the tuna fish caught by this operation mode is smaller in size and the discarding rate is extremely high which will affect the overall profits of the fishermen. The research will investigate how the fishermen make the choice of the operation mode in the dilemma between dolphin sets which cause dolphins-bycatch and non-dolphin sets which result in tuna-discarding, In addition, if managers can ban dolphin sets or non-dolphin sets to maximize the profit of the fishermen and maintain the ecological balance between tuna and dolphins.

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

<p>There have been few efforts to evaluate the actual and perceived effectiveness of environmental management programs created by consensus-based, multi-stakeholder negotiation or negotiated rulemaking. Previous evaluations have used perceived success among participants as a proxy for actual effectiveness, but seldom have investigated the ecological outcomes of these negotiations. Fewer still, if any, have compared the actual and perceived outcomes. Here I evaluate and compare the social and ecological outcomes of the negotiated rulemaking process of marine mammal take reduction planning. Take reduction planning is mandated by the U.S. Marine Mammal Protection Act (MMPA) to reduce the fisheries-related serious injuries and mortalities of marine mammals (bycatch) in U.S. waters to below statutory thresholds. Teams of fishermen, environmentalists, researchers, state and federal managers, and members of Regional Fisheries Management Councils and Commissions create consensus-based rules to mitigate bycatch, called Take Reduction Plans. There are six active Take Reduction Plans, one Take Reduction Strategy consisting of voluntary measures, and one plan that was never implemented. It has been 20 years since marine mammal take reduction planning was incorporated into the MMPA. Early evaluations were promising, but identified several challenges. In the past decade or more, the National Marine Fisheries Service (NMFS) has implemented measures to set up the teams for success.</p><p>I used data from formal Stock Assessment Reports to assess and rank the actual ecological success of five Take Reduction Plans (Harbor Porpoise, Bottlenose Dolphin, Atlantic Large Whale, Pelagic Longline, and Pacific Offshore Cetacean) in mitigating the bycatch of 17 marine mammal stocks. In addition, I employed social science data collection and analytical methods to evaluate Take Reduction Team participants' opinions of the take reduction negotiation process, outputs, and outcomes with respect to the ingredients required for successful multi-stakeholder, consensus-based negotiation (team membership, shared learning, repeated interactions, facilitated meetings, and consensus-based outputs). These methods included surveying and interviewing current and former Take Reduction Team participants; using Structural Equation Models (SEMs) and qualitative methods to characterize participant perceptions across teams and stakeholder groups; and identifying and exploring the reasons for similarities and differences among respondents, teams, and stakeholder groups. I also employed SEMs to quantitatively examine the relationship between actual and perceived ecological success, and contrasted actual and perceived outcomes by comparing their qualitative rankings.</p><p>Structural Equation Models provided a valid framework in which to quantitatively examine social and ecological data, in which the actual ecological outcomes were used as independent predictors of the perceived outcomes. Actual improvements in marine mammal bycatch enhanced stakeholder opinions about the effectiveness of marine mammal Take Reduction Plans. The marine mammal take reduction planning process has all of the ingredients necessary for effective consensus-based, multi-stakeholder negotiations (Chapter 2). It is likely that the emphasis that the National Marine Fisheries Service places on empirical information and keeping stakeholders informed about bycatch, marine mammal stocks, and fisheries facilitated this relationship. Informed stakeholders also had relatively accurate perceptions of the actual ecological effectiveness of the Take Reduction Plans (Chapter 3). The long timeframes over which the teams have been meeting generally have increased cooperation. The professionally trained, neutral facilitators have produced fair negotiations, in which most individuals felt they had an opportunity to contribute. Participant views of fairness significantly influenced their satisfaction with Take Reduction Plans, which significantly affected their perceptions about the effectiveness of those plans (Chapter 2). The mandate to create a consensus-based output has, for the most part, minimized defections from the negotiations and facilitated stakeholder buy-in. </p><p>In general, marine mammal take reduction planning is a good negotiated rulemaking process, but has produced mixed results (Chapters 1 and 2). Successful plans were characterized by straightforward regulations and high rates of compliance. Unsuccessful plans had low compliance with complex regulations and sometimes focused on very small stocks. Large teams and those in the northeastern U.S. (Maine to North Carolina) were least successful at reducing bycatch, which was reflected in stakeholder views of the effectiveness of these teams. Take Reduction Team negotiations have not always produced practical or enforceable regulations. Implementation of take reduction regulations is critical in determining plan success and identifying effective mitigation measures, but because of a lack of monitoring, has not been characterized consistently across most teams. Additionally, elements like the "Other Special Measures Provision" in the Harbor Porpoise Take Reduction Plan have undermined the negotiation process by allowing the National Marine Fisheries Service to alter consensus-based elements without consensus from the team, which has led to hostility, mistrust, and frustration among stakeholders. </p><p>The final chapter of this dissertation provides recommendations to improve the outcomes and make them more consistent across teams. I based these recommendations on the information gathered and analyzed in the first three chapters. They are grouped into four broad categories - team membership, social capital, fairness, and plan implementation. If the National Marine Fisheries Service implements these suggestions, both perceived and actual ecological effectiveness of marine mammal Take Reduction Teams should improve, allowing these teams to fulfill their maximum potential.</p> / Dissertation

Concerns about declines in marine biodiversity led to the creation of marine protected areas and spatial fishery closures as tools for recovery. Yet many marine conservation areas suffer low levels of compliance from diverse fishing populations, including recreational fishers. Little research quantifies levels of recreational fisher compliance and its drivers, especially in temperate marine environments, despite the prevalence of this kind of fishing in some regions. This thesis addresses this knowledge gap through a study of recreational fisher compliance in Rockfish Conservation Areas (RCAs) in British Columbia, Canada. One hundred and sixty four RCAs were implemented between 2003 and 2007 and now cover 4847.2 km2. These conservation areas were created in response to widespread concern from fishers and non-governmental organizations about inshore rockfish population declines. However, recent research suggested that recreational fisher compliance might be low. This thesis had two goals: 1) contribute to knowledge about, and develop methods of assessing, non-compliance within marine conservation areas, and 2) address the immediate problem of suspected recreational non-compliance in RCAs. I had the following objectives: 1) Assess ecological and social RCA effectiveness to date, using a framework for improving governance from the literature on common pool resources; 2) Assess recreational fisher knowledge and perceptions of RCAs, and 3) Quantify non-compliance and social and ecological compliance drivers in RCAs. Methods included a literature review, structured surveys with 325 recreational fishers at 16 locations in the Salish Sea (Southern Gulf Islands and Victoria area), and trail camera monitoring in 42 coastal locations (both RCAs and unprotected sites). Results show that recreational fisher knowledge and compliance to RCA regulations is low. The assessment of social and ecological effectiveness shows much room for management improvement for recreational fisheries. This finding is supported by my survey and trail camera data. I found that 25.5% of recreational fishers had never heard of RCAs and ~60% were unsure of RCA locations. The total non-compliance rate was 23% in RCAs. Seventy nine percent of trail camera monitored RCA sites showed confirmed or probable fishing activity, with no significant difference between fishing effort inside and outside RCAs. However, 77% of fishers surveyed believed that rockfish conservation is necessary with advertising, fisher education, and increased monitoring offered as solutions to non-compliance. I recommend managers implement a public outreach and education campaign to address low levels of compliance. This study suggests that positive perceptions of marine conservation areas and conservation initiatives are not enough to create high compliance. Educating stakeholders and creating high levels of awareness should be an essential first step when creating marine conservation areas. My research offers important insights into the study of non-compliance, and the immediate problem of recreational non-compliance in BC’s RCAs. My successful use of a simple and cost/time efficient multiple methods approach to assessing compliance provides robust tools for future compliance analyses, and hence provides a valuable contribution to the compliance literature. The study also suggests that trail camera monitoring could be a promising new method for monitoring coastal conservation areas. / Graduate / 0768 / 0792 / 0306

<p>Sea turtles are long lived marine species that are currently endangered because their life history and population dynamics hinder them from withstanding modern anthropogenic threats. Worldwide, fisheries bycatch in on the major threats to the survival of sea turtles and that is also the case in the Eastern Pacific. To establish regional conservation priorities for the mitigation of bycatch, it is essential to first obtain a comprehensive picture of the regional sea turtle bycatch situation. This comprehensive analysis was lacking for the Eastern Pacific; therefore one component of this dissertation (the first chapter) is focused on delivering a regional bycatch analysis for the Eastern Pacific. A literature review was conducted to obtain numbers of turtles captured, frequencies, bycatch and mortality rates per species and country in trawl, longline, and gillnet fisheries, and to compile results of mitigation measures. Moreover, estimates for current annual capture rates in trawl fisheries were obtained and compared with population numbers. </p><p>This regional bycatch used all the information compiled and synthesized to give conservation priorities at the regional level. The review underlines the high bycatch rates in trawls for Costa Rica, Guatemala, and El Salvador and the detrimental impact that these captures could have specially for hawksbill Eretmochelys imbricata due to its reduced population numbers and for green turtle Chelonia mydas due to its highest mortality rate. It also emphasizes the continuous lack of use of TEDs as a bycatch mitigation measure. In longline fisheries, the review identifies the high bycatch rates in pelagic longline fisheries of Costa Rica, Ecuador, and Nicaragua in a global context but given that olive ridley Lepidochelys olivacea is the most common species captured in these countries, it highlights the capture of loggerhead Caretta caretta and leatherback Dermochelys coriacea off Peru and Chile due to their small population numbers. Bottom longlines have high mortality rates compared with pelagic longlines in the region and the review identifies a need for further research in this area due to the scarce information but high mortality rates. The review also noted that some mitigation measures for pelagic longlines like circle hooks and hooks with appendages could bring improvements in the mitigation of bycatch in longline fisheries in the region, there is still considerable work to be done in technology transfer, sea turtle handling, and estimates of post-release mortality rates. </p><p>For gillnet fisheries, the most important highlight is how little information exists for the region given the high rates of bycatch for sea turtles in this gear. However, the difficulties of studying bycatch in highly dynamic and artisanal fisheries are recognized as the major impediment for this situation. Nevertheless, the high bycatch rates in areas where sea turtles congregate in high numbers like in foraging grounds for loggerhead in Baja California, Mexico and for greens in Paracas and Sechura, Peru, calls for either gear modifications (which has not been that successful), change of gear, or areas closed for gillnets. </p><p>The second half of the dissertation is focused on foraging ecology of oceanic sea turtles in the Southeast Pacific Ocean. Sea turtles in the oceanic stage are the least known stage due to the difficulty of accessing these individuals. However, it is a very important stage in the life cycle and can be critical for the population dynamics of sea turtles as some population models have shown. Therefore, this dissertation is filling a gap in the life cycle of sea turtle populations in the Eastern Pacific. </p><p>To study foraging ecology, we used Stable Isotope Analysis (SIA) of turtle tissues as well as potential prey items from the oceanic realm. SIA is a great tool because it gives an integrated view, from days to weeks, of prey from a consumer tissue. SIA also can be used to link consumers to habitats when elements that have spatial trends are used. In chapter two, we investigate the foraging ecology of three species of sea turtles to compare trophic status and to observe if spatial patterns were shown in the SIA signatures of sea turtles. To our knowledge this is the first study employing SIA to research the ecology of three species of sea turtles from the same time and space. Our results show that spatial patterns in delta15N and delta13C were observed in sea turtle's tissues as correlations with latitude. We also found that loggerhead's signatures differed significantly from green and olive ridleys, especially in terms of delta15N. Loggerheads had higher values of delta15N and also a wider nitrogen trophic niche. Greens and olive ridleys were similar in isotopic nitrogen values but they were significantly different in carbon. When analyzing a smaller group of animals captured in a more restricted area, nitrogen differences were not found which suggests that latitudinal spatial patterns play an important role in the nitrogen signature. On the contrary, carbon signatures still differed among turtles in the restricted area which suggest that the inshore-offshore trend is strong and made us conclude that loggerheads are restricted to oceanic areas but that greens and olive ridleys could be using both coastal and oceanic areas.</p><p>In chapter three, we conduct a mixing model analysis using the Bayesian program SIAR to identify the most important prey items for green, olive ridley, and loggerhead off Peru. Also, we wanted to identify the contribution of longline baits in the diet of oceanic turtles. The analysis was restricted to the central zone of our study area to avoid spatial trends in nitrogen. To use as sources in the model, we collected potential prey items offshore Peru during trips on longline fishing vessels and obtained their stable isotope signatures. Results from our mixing models show that for greens and olive ridleys, crustaceans, mollusks, and coastal Ulva (indicator of coastal prey) were the only important food items. In the case of greens, crustaceans had a very high proportional contribution and due to the fact that nitrogen values of crustaceans were the lowest ones among the sources it seems that greens would be eating in a lower trophic level. The importance of coastal Ulva for greens and olive ridleys is a confirmation of our findings from chapter two where we suggest that these two species could be using oceanic as well as coastal areas. </p><p>Results for loggerheads showed cnidarians, mollusks, mackerel and squid bait as foraging items and highlights the differences among this species and the other two. The lack of importance of coastal Ulva again suggests that loggerheads remain only in oceanic areas off Peru. Moreover, the importance of mackerel and squid, the most common longline baits, suggests this species is the one interacting the most with longline fisheries and that cumulative effect of multiple interactions could have a detrimental effect in this population.</p> / Dissertation

Estimating the risk associated with species and pathogen movements involves considerable uncertainty. One key uncertainty concerns the extent and frequency of human-mediated species and pathogen movements relative to the distribution of recipient ecosystems. Baitfish use in Ontario, Canada is one of many pathways with the potential to introduce and spread biota to beyond their current geographic range. To determine the biological risk associated with baitfish use, models were used to estimate the probability of species occurrences throughout pathway levels, from the commercial harvest level, to retail tank and angler purchases, to movement and release by the end-user (i.e., the angler). Vector activity, as the primary contributor of species movements and introductions associated with this pathway, was modeled within a spatial interaction framework that incorporated landscape structure (e.g., the distribution of angling populations, lake size and sportfish richness, and their physical separation via least-cost routing of transportation networks) to predict the extent of movement. Agent-based models of vector activity were used to relate vector movements to region-specific probability thresholds of risk activity. Model outputs were used to estimate the movement and introduction of species and pathogens to lake ecosystems resulting from a variety of infection scenarios. Species results identified a pronounced reduction in the probability of non-target species occurrences throughout pathway levels. However, the occurrence of biological invaders and other non-target fishes at retail levels implied incidental bycatch throughout the pathway. Relatively short, frequent vector movements associated with incidentally purchased species were very likely, yet would not contribute to species range expansions due to the homogeneity of biological communities at those levels. However, rarer, yet considerably lengthier, vector movements associated with key species and pathogens implied the potential for low-probability, long-distance species and pathogen movements resulting from human activities.

Estimating the risk associated with species and pathogen movements involves considerable uncertainty. One key uncertainty concerns the extent and frequency of human-mediated species and pathogen movements relative to the distribution of recipient ecosystems. Baitfish use in Ontario, Canada is one of many pathways with the potential to introduce and spread biota to beyond their current geographic range. To determine the biological risk associated with baitfish use, models were used to estimate the probability of species occurrences throughout pathway levels, from the commercial harvest level, to retail tank and angler purchases, to movement and release by the end-user (i.e., the angler). Vector activity, as the primary contributor of species movements and introductions associated with this pathway, was modeled within a spatial interaction framework that incorporated landscape structure (e.g., the distribution of angling populations, lake size and sportfish richness, and their physical separation via least-cost routing of transportation networks) to predict the extent of movement. Agent-based models of vector activity were used to relate vector movements to region-specific probability thresholds of risk activity. Model outputs were used to estimate the movement and introduction of species and pathogens to lake ecosystems resulting from a variety of infection scenarios. Species results identified a pronounced reduction in the probability of non-target species occurrences throughout pathway levels. However, the occurrence of biological invaders and other non-target fishes at retail levels implied incidental bycatch throughout the pathway. Relatively short, frequent vector movements associated with incidentally purchased species were very likely, yet would not contribute to species range expansions due to the homogeneity of biological communities at those levels. However, rarer, yet considerably lengthier, vector movements associated with key species and pathogens implied the potential for low-probability, long-distance species and pathogen movements resulting from human activities.

Thirteen elasmobranch species were collected during a four year seine-net survey of the intertidal margins of Moreton Bay, a large subtropical embayment in southeast Queensland, Australia. The inshore elasmobranch fauna of Moreton Bay is relatively species rich in comparison to sites elsewhere in Australia, emphasising the regional importance of this ecosystem. Stingrays were the most common large predators in the intertidal, with overall catches dominated numerically by the blue-spotted maskray Neotrygon kuhlii (53.8%) and the estuary stingray Dasyatis fluviorum (22.2%). The biological and demographic characteristics of these two species were examined in detail. Neotrygon kuhlii ranged in size from 11.5 – 46.5 cm disc width (WD), with 50% maturity in females at 31.4 cm WD and 6.32 years old and at 29.4 cm WD and 3.95 years in males. Neotrygon kuhlii has a synchronous annual reproductive cycle, producing one litter of 1 – 3 pups (mean of 1.67 ± 0.71 S.D.) in the late Austral summer after a four month gestation. Maximum age estimates of 13 and 10 years were obtained from females and male N. kuhlii, respectively. Annual band pair deposition was confirmed through the recapture of four wild calcein-injected individuals from 22.7 to 30.2 cm WD. A three parameter power function provided the best statistical fit to age-at-size data for both sexes, providing parameter estimates of y0 = 163.13, a = 58.52 and b = 0.58 for females and y0 = 165.13, a = 59.02 and b = 0.54 in males. Individual growth rates obtained from tagged specimens were not qualitatively different to modelled growth predictions. Tagging studies produced a total recapture rate of 16.1%, with individual rays at liberty for up to 1081 days. Direct estimates of instantaneous mortality for N. kuhlii were derived by creating catch curves for both sexes from age-frequency keys. Mortality was estimated at 0.171 ± 0.024.yr-1 S.E. in females, corresponding with a population growth rate of 1.00.yr-1 based on deterministic matrix demographic model predictions, and 0.345 ± 0.022.yr-1 S.E. in males. Seven age-independent and two age-dependent indirect mortality estimates produced negative population growth rates of 0.84 to 0.98.yr-1. Elasticity results were relatively robust to mortality estimates, with juvenile survivorship contributing 74-75% of total elasticity under all scenarios. Dasyatis fluviorum is endemic to near-shore, estuarine and riverine habitats along the eastern coast of Australia. Previous records of the species from northern Australia and New Guinea appear to be misidentifications of other, similar species. Dasyatis fluviorum was caught at 15.5 cm to 76.2 cm WD in Moreton Bay, with 50% maturity occurring at 63 cm WD (13.40 years) in females and 41.2 cm WD (6.97 years) in males. Maximum age estimates of 21 and 16 years were obtained from females and males, respectively. The Gompertz growth function provided the best fit to estimated age data in female D. fluviorum, providing parameter estimates of WD∞ = 100.3 cm, k = 0.09.yr-1 and t0 = 5.66. The modified two-parameter von Bertalanffy growth function provided the best fit to male size-at-age data, providing parameter estimates of WD∞ = 73.4 cm, k = 0.10.yr-1 and b = 0.86. An annual reproductive cycle in female D. fluviorum was hypothesised based on preliminary reproductive data. Fecundity estimates were derived from the related D. americana for input into deterministic and stochastic demographic models. Six out of nine indirect mortality estimates produced positive population growth in deterministic models, with a probabilistic estimate of 1.02.yr-1. Elasticity results were robust to model structure, mortality and fecundity estimates, with juvenile survivorship comprising 74-78% of total elasticity under all scenarios. Both N. kuhlii and D. fluviorum provide interesting case studies in elasmobranch conservation. Neotrygon kuhlii is a common bycatch of demersal prawn-trawl fisheries in Australia. Although mandatory turtle exclusion devices (TEDs) exclude most large vertebrates from trawl catches in Australian waters, their benefits in the reduction of smaller elasmobranch bycatch has not been empirically tested. The results of deterministic demographic models show that TEDs can, in principle, mitigate the impacts of trawl fisheries by partially excluding highly-elastic large juvenile age-classes. However, N. kuhlii is the largest of the four Neotrygon species found in Australian waters and bycatch of the three smaller species may be less reduced by current bycatch reduction technologies. Dasyatis fluviorum is affected by a suite of anthropogenic threats in its near-shore and estuarine habitats including commercial and recreational fisheries, habitat modification and pollution. Within Moreton Bay, 10.8% of the surveyed population bore evidence of past interactions with fisheries as evidenced by retained hooks or mutilated tails. Deep-hooking resulted in significant pathological effects including fibrocollagenous scar tissue masses, peritonitis and hepatitis. Stochastic demographic scenarios were created to model the potential effects of low (0.02 yr-1), medium (0.05 yr-1) and high (0.10 yr-1) rates of additive anthropogenic mortality to simulate stage-specific conservation interventions on D. fluviorum. Removing anthropogenic mortality on juvenile age-classes provided the largest benefits in terms of reducing population decline. The probability of the species’ conservation status declining further to Endangered, based on IUCN criteria, ranged from 39% to 100% under these mortality scenarios if no conservation measures were applied.

Thirteen elasmobranch species were collected during a four year seine-net survey of the intertidal margins of Moreton Bay, a large subtropical embayment in southeast Queensland, Australia. The inshore elasmobranch fauna of Moreton Bay is relatively species rich in comparison to sites elsewhere in Australia, emphasising the regional importance of this ecosystem. Stingrays were the most common large predators in the intertidal, with overall catches dominated numerically by the blue-spotted maskray Neotrygon kuhlii (53.8%) and the estuary stingray Dasyatis fluviorum (22.2%). The biological and demographic characteristics of these two species were examined in detail. Neotrygon kuhlii ranged in size from 11.5 – 46.5 cm disc width (WD), with 50% maturity in females at 31.4 cm WD and 6.32 years old and at 29.4 cm WD and 3.95 years in males. Neotrygon kuhlii has a synchronous annual reproductive cycle, producing one litter of 1 – 3 pups (mean of 1.67 ± 0.71 S.D.) in the late Austral summer after a four month gestation. Maximum age estimates of 13 and 10 years were obtained from females and male N. kuhlii, respectively. Annual band pair deposition was confirmed through the recapture of four wild calcein-injected individuals from 22.7 to 30.2 cm WD. A three parameter power function provided the best statistical fit to age-at-size data for both sexes, providing parameter estimates of y0 = 163.13, a = 58.52 and b = 0.58 for females and y0 = 165.13, a = 59.02 and b = 0.54 in males. Individual growth rates obtained from tagged specimens were not qualitatively different to modelled growth predictions. Tagging studies produced a total recapture rate of 16.1%, with individual rays at liberty for up to 1081 days. Direct estimates of instantaneous mortality for N. kuhlii were derived by creating catch curves for both sexes from age-frequency keys. Mortality was estimated at 0.171 ± 0.024.yr-1 S.E. in females, corresponding with a population growth rate of 1.00.yr-1 based on deterministic matrix demographic model predictions, and 0.345 ± 0.022.yr-1 S.E. in males. Seven age-independent and two age-dependent indirect mortality estimates produced negative population growth rates of 0.84 to 0.98.yr-1. Elasticity results were relatively robust to mortality estimates, with juvenile survivorship contributing 74-75% of total elasticity under all scenarios. Dasyatis fluviorum is endemic to near-shore, estuarine and riverine habitats along the eastern coast of Australia. Previous records of the species from northern Australia and New Guinea appear to be misidentifications of other, similar species. Dasyatis fluviorum was caught at 15.5 cm to 76.2 cm WD in Moreton Bay, with 50% maturity occurring at 63 cm WD (13.40 years) in females and 41.2 cm WD (6.97 years) in males. Maximum age estimates of 21 and 16 years were obtained from females and males, respectively. The Gompertz growth function provided the best fit to estimated age data in female D. fluviorum, providing parameter estimates of WD∞ = 100.3 cm, k = 0.09.yr-1 and t0 = 5.66. The modified two-parameter von Bertalanffy growth function provided the best fit to male size-at-age data, providing parameter estimates of WD∞ = 73.4 cm, k = 0.10.yr-1 and b = 0.86. An annual reproductive cycle in female D. fluviorum was hypothesised based on preliminary reproductive data. Fecundity estimates were derived from the related D. americana for input into deterministic and stochastic demographic models. Six out of nine indirect mortality estimates produced positive population growth in deterministic models, with a probabilistic estimate of 1.02.yr-1. Elasticity results were robust to model structure, mortality and fecundity estimates, with juvenile survivorship comprising 74-78% of total elasticity under all scenarios. Both N. kuhlii and D. fluviorum provide interesting case studies in elasmobranch conservation. Neotrygon kuhlii is a common bycatch of demersal prawn-trawl fisheries in Australia. Although mandatory turtle exclusion devices (TEDs) exclude most large vertebrates from trawl catches in Australian waters, their benefits in the reduction of smaller elasmobranch bycatch has not been empirically tested. The results of deterministic demographic models show that TEDs can, in principle, mitigate the impacts of trawl fisheries by partially excluding highly-elastic large juvenile age-classes. However, N. kuhlii is the largest of the four Neotrygon species found in Australian waters and bycatch of the three smaller species may be less reduced by current bycatch reduction technologies. Dasyatis fluviorum is affected by a suite of anthropogenic threats in its near-shore and estuarine habitats including commercial and recreational fisheries, habitat modification and pollution. Within Moreton Bay, 10.8% of the surveyed population bore evidence of past interactions with fisheries as evidenced by retained hooks or mutilated tails. Deep-hooking resulted in significant pathological effects including fibrocollagenous scar tissue masses, peritonitis and hepatitis. Stochastic demographic scenarios were created to model the potential effects of low (0.02 yr-1), medium (0.05 yr-1) and high (0.10 yr-1) rates of additive anthropogenic mortality to simulate stage-specific conservation interventions on D. fluviorum. Removing anthropogenic mortality on juvenile age-classes provided the largest benefits in terms of reducing population decline. The probability of the species’ conservation status declining further to Endangered, based on IUCN criteria, ranged from 39% to 100% under these mortality scenarios if no conservation measures were applied.

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