Feeding biomechanics and foraging behavior are likely contributors to loggerhead sea turtle (Caretta caretta) bycatch in the pelagic longline fishery. To investigate these contributions, loggerhead bite performance was measured in several size classes of captive-reared juveniles, captive sub-adults and adults, as well as wild loggerheads. A kinematic study was conducted to investigate loggerhead interactions with modified longline hooks. Kinematic and behavioral variables were assessed in relation to five longline hooks to determine if loggerhead feeding behavior is modulated relative to hook type, size, and offset. The bite force study demonstrated that mean maximum post-hatchling bite force was 2.5N and mass was the best predictor of post-hatchling bite force. Mean maximum bite force of juveniles with mean straight carapace length (SCL) of 12, 31, 44, and 65 cm were 27, 152, 343, and 374 N, respectively. Sub-adult and adult mean maximum bite force was 575 N. Maximum bite force had a positive linear relationship with all head and body morphometrics (P<0.001). Carapace width was the best predictor of bite force throughout ontogeny. The kinematic study demonstrated no differences between hook treatments in all kinematic variables analyzed. The results of this study suggest loggerhead feeding behavior may be stereotypical. Only 33% of all interactions resulted in “hooking” events. “Hooking” was lowest in 16 gage circle hooks with no offset and the 18 gage circle hooks with 10°offset which may be indicative of a lower possibility of the turtle drowning. “Hooking” was highest in the 16 gage circle hooks with 10°offset. The proportion of turtles “hooked” in the mouth was significantly greater than those “hooked” in the throat (P=0.001). Sixteen gage circle hooks with 10° offset had the highest percentage of throat “hooking”, and the 18 gage circle hooks without offset resulted in the lowest percentage of throat hooking. When interacting with J hooks with a 25° offset (9 gage), turtles mostly oriented their head away from the hook offset; however, when interacting with the 16 and 18 gage circle hooks with 10° offset, turtles mostly oriented their heads toward the hook offset. These data suggest that turtles may distinguish between small and large offsets, and may modulate their feeding behavior accordingly. Alternatively, turtles may be detecting hook size or hook shape. A more thorough characterization of loggerhead bite performance and feeding kinematics will be useful when developing or modifying longline fishery gear aimed at reducing loggerhead bycatch.

Feeding biomechanics and foraging behavior are likely contributors to loggerhead sea turtle (Caretta caretta) bycatch in the pelagic longline fishery. To investigate these contributions, loggerhead bite performance was measured in several size classes of captive-reared juveniles, captive sub-adults and adults, as well as wild loggerheads. A kinematic study was conducted to investigate loggerhead interactions with modified longline hooks. Kinematic and behavioral variables were assessed in relation to five longline hooks to determine if loggerhead feeding behavior is modulated relative to hook type, size, and offset. The bite force study demonstrated that mean maximum post-hatchling bite force was 2.5N and mass was the best predictor of post-hatchling bite force. Mean maximum bite force of juveniles with mean straight carapace length (SCL) of 12, 31, 44, and 65 cm were 27, 152, 343, and 374 N, respectively. Sub-adult and adult mean maximum bite force was 575 N. Maximum bite force had a positive linear relationship with all head and body morphometrics (P<0.001). Carapace width was the best predictor of bite force throughout ontogeny. The kinematic study demonstrated no differences between hook treatments in all kinematic variables analyzed. The results of this study suggest loggerhead feeding behavior may be stereotypical. Only 33% of all interactions resulted in “hooking” events. “Hooking” was lowest in 16 gage circle hooks with no offset and the 18 gage circle hooks with 10°offset which may be indicative of a lower possibility of the turtle drowning. “Hooking” was highest in the 16 gage circle hooks with 10°offset. The proportion of turtles “hooked” in the mouth was significantly greater than those “hooked” in the throat (P=0.001). Sixteen gage circle hooks with 10° offset had the highest percentage of throat “hooking”, and the 18 gage circle hooks without offset resulted in the lowest percentage of throat hooking. When interacting with J hooks with a 25° offset (9 gage), turtles mostly oriented their head away from the hook offset; however, when interacting with the 16 and 18 gage circle hooks with 10° offset, turtles mostly oriented their heads toward the hook offset. These data suggest that turtles may distinguish between small and large offsets, and may modulate their feeding behavior accordingly. Alternatively, turtles may be detecting hook size or hook shape. A more thorough characterization of loggerhead bite performance and feeding kinematics will be useful when developing or modifying longline fishery gear aimed at reducing loggerhead bycatch.

Offshore culture becomes the most attractive industry in last decades because of overfishing and excessively pumping groundwater causing land subsidence social problems. Oyster culture is one of offshore culture with several advantages such as easy set-up and without feeding cost. In this study, we focus on a longline-style oyster aquaculture system because it is recyclable, high growing efficiency and advanced technique against traditional tidal flat culture. This study establishes a numerical model through a lumped mass method, then employs fourth order Runge-Kutta method to solve the system of motion equations and evaluates the tension on the anchor rope. The results show the discrepancy between the numerical model and experimental data is lower than 4% in current-only situation, and similarly in wave-only situation the discrepancy is lower than 6%. The comparison results indicate that the numerical model is capable to predict the environmental loadings on longline-style oyster culture system. An in-situ case study of a longline-style oyster aquaculture system via regular and random waves, located in the Penghu Bay, is investigated based on the sea-state, Chebi Typhoon occurred in June, 2001, causing a catastrophic damage to the cage aquaculture. The conclusions of dynamic responses of the case study may be utilized as guidance for the local oyster farmers to build and protect their oyster culture system in the Bay.

Longline fishing is the most common elasmobranch capture method in the world, both for commercial fishing, and to a lesser extent for scientific surveys. The capture of an animal on a longline initiates a series of physiological responses designed to promote survivorship in the short term, but if unchecked, can cause reduced individual fitness and/or mortality in the long term. Given widespread declines in shark populations, an improved understanding of the physiological costs of longline capture is needed. The aim of this thesis was to investigate the physiological response of sharks to capture and restraint, to assess novel, non-invasive alternatives to scientific longline surveys, and to generate scientific insight into poorly understood elasmobranch populations in The Bahamas. The results presented herein suggest that some species of shark are able to recover from the physiological stress of capture despite the presence of persistent negative stimuli. Tonic immobility was assessed as a means of generating baseline blood chemistry data, but was found to be inappropriate given that it increases the magnitude of physiological perturbation in the short term. To avoid the stress of capture altogether, Baited Remote Underwater Video Surveys (BRUVS) were considered as a non-invasive alternative to capture based surveys, however, it was concluded that they lack the resolution necessary to answer fine scale demographic questions. For the Caribbean reef shark, longline surveys yielded high resolution data allowing the identification of fine scale spatiotemporal shifts in demographic population structure with minimal cost (mortality). Nevertheless, the ethics of using capture based surveys on sensitive species are questionable when alternative techniques are available. Deep water sharks caught on longline surveys exhibited high mortality rates, however, for these very poorly understood species moribund specimens have great scientific value which in some cases can offset the high ecological costs of the surveys. The results presented in this thesis highlight the on-going need for improved biological and ecological research into the majority of elasmobranch populations, particularly with regards to anthropogenic interactions such as capture. Given the tenuous conservation status of many species, the acquisition of applied, management focused data should remain the priority of elasmobranch scientists.

Foram analisados dados referentes às capturas do tubarão-azul (Prionace glauca) pela frota espinheleira baseada na localidade de Itajaí (SC), operando nas regiões Sudeste e Sul do Brasil e em águas internacionais adjacentes, entre os anos de 1996 a 2002. Estes foram obtidos na forma de mapas de bordo, fichas de desembarque e através de embarques nesta frota. Com as informações biológicas dos cruzeiros ajustou-se equações para a conversão dos dados de peso eviscerado dos animais capturados das fichas de desembarques para comprimento total e peso total. Após convertidos, elaborou-se a distribuição de frequência das classes de comprimento mensais e a análise da captura acumulada. Com dados dos mapas de bordo, analisouse a captura por unidade de esforço (CPUE) em peso e em número de indivíduos. Posteriormente desenvolveu-se modelagem estatística com o uso do modelo linear generalizado (GLM) para avaliar a magnitude do efeito das variáveis temporais e espaciais sobre as CPUE’s. Verificou-se que o recrutamento por pesca ocorre entre maio e novembro, a ampliação da área de cópula para os 34º S, que as variáveis temporais influenciam mais nas CPUE’s do que as espaciais, a correlação positiva da latitude com as CPUE’s e negativa para a longitude e a necessidade de conservação deste importante grupo de predadores. / This study analyzed data from the capture of blue shark (Prionace glauca) by the longline fleet based in Itajaí, State of Santa Catarina, Brazil, operating in south and southeast regions and in international neighboring waters from 1996 to 2002. The data were collected in the form of logbooks, landing sheets and through research cruises personally conducted aboard the commercial fleet. Based on the biological information gathered from the cruises, equations were calculated in order to convert the data of carcass weight captured and listed in the landing sheets for total length and total weight. After data conversion, length frequency for each month and the analysis of accumulated capture was rebuilt. With the data from logbooks, CPUE/1000 hooks were analyzed in terms of kg and the number of individuals plotting of results. Statistical modeling was then developed with the use of GLM to assess the effect of time and space variables in CPUE’s. At the time of fishery recruitment between May and November, the following were observed: (i) the expansion of the mating area to 34º S (ii) time variables influenced more the CPUE’s than the space variables (iii) a positive correlation of the latitude with the CPUE’s and a negative correlation for longitude and (iv) the need for conservation of this important group of predators.

Foram analisados dados referentes às capturas do tubarão-azul (Prionace glauca) pela frota espinheleira baseada na localidade de Itajaí (SC), operando nas regiões Sudeste e Sul do Brasil e em águas internacionais adjacentes, entre os anos de 1996 a 2002. Estes foram obtidos na forma de mapas de bordo, fichas de desembarque e através de embarques nesta frota. Com as informações biológicas dos cruzeiros ajustou-se equações para a conversão dos dados de peso eviscerado dos animais capturados das fichas de desembarques para comprimento total e peso total. Após convertidos, elaborou-se a distribuição de frequência das classes de comprimento mensais e a análise da captura acumulada. Com dados dos mapas de bordo, analisouse a captura por unidade de esforço (CPUE) em peso e em número de indivíduos. Posteriormente desenvolveu-se modelagem estatística com o uso do modelo linear generalizado (GLM) para avaliar a magnitude do efeito das variáveis temporais e espaciais sobre as CPUE’s. Verificou-se que o recrutamento por pesca ocorre entre maio e novembro, a ampliação da área de cópula para os 34º S, que as variáveis temporais influenciam mais nas CPUE’s do que as espaciais, a correlação positiva da latitude com as CPUE’s e negativa para a longitude e a necessidade de conservação deste importante grupo de predadores. / This study analyzed data from the capture of blue shark (Prionace glauca) by the longline fleet based in Itajaí, State of Santa Catarina, Brazil, operating in south and southeast regions and in international neighboring waters from 1996 to 2002. The data were collected in the form of logbooks, landing sheets and through research cruises personally conducted aboard the commercial fleet. Based on the biological information gathered from the cruises, equations were calculated in order to convert the data of carcass weight captured and listed in the landing sheets for total length and total weight. After data conversion, length frequency for each month and the analysis of accumulated capture was rebuilt. With the data from logbooks, CPUE/1000 hooks were analyzed in terms of kg and the number of individuals plotting of results. Statistical modeling was then developed with the use of GLM to assess the effect of time and space variables in CPUE’s. At the time of fishery recruitment between May and November, the following were observed: (i) the expansion of the mating area to 34º S (ii) time variables influenced more the CPUE’s than the space variables (iii) a positive correlation of the latitude with the CPUE’s and a negative correlation for longitude and (iv) the need for conservation of this important group of predators.

Data collected by Australian observers, combined with logbook data supplied by all Japanese vessels fishing in the Australian Fishing Zone were used to estimate the total seabird catch and catch rates (and associated variances) within the Australian Fishing Zone by season and area. The species composition of subsamples of captured seabirds was used in conjunction with the estimates of total by-catch to provide estimates of by-catch by species. The total by-catch of all seabird species by Japanese longline within Australian waters was estimated to be 2,981 (cv 17%) for the 1992 fishing year, 3,590 (cv 15%) in 1993 and 2,817 (cv 19%) in 1994. However, the observed seabird bycatch may underestimate the total number of seabirds killed by 27%. The increase in total seabird by-catch between 1992 and 1993 is partly due to the use of monofilament nylon longline gear by two vessels in 1993, and the decrease from 1993 to 1994 was mainly due to a corresponding reduction in fishing effort. For the three years examined, 78% of the total seabird by-catch was albatrosses, with black-browed albatross (Diomedea melanophrys) and shy albatross (D. cauta) caught in the greatest numbers. Catches of yellow-nosed albatross (D. chlororhynchos), wandering albatross (D. exulans}, and grey-headed albatross (D. chrysostoma) were also substantial. The proportions of individual species caught showed considerable inter-annual variability. Most seabirds caught and killed by longline fishing are captured during line setting. Data collected by the observers were also used to determine the influence of various environmental factors and mitigation measures on seabird catch rates. Generalised linear models were used to determine the statistical significance of the effect of each factor on the seabird catch rate. Results show that the environmental factor that has the most influence is whether line setting was carried out at night or during the day. For the data examined, the chance of catching seabirds during day sets was five times greater than for night sets. For night sets, the chance of catching seabirds during the full half-phase of the moon was five times greater than during the new half-phase. Other environmental factors with significant effects were the area and season fished. Wind, cloud and sea conditions were not found to have a significant influence. Considerable variation in the seabird by-catch rate among vessels was found, which is probably due to differences in their implementation of mitigation measures, as well as the clumped distribution of seabirds by area and time. Interannual variation in the by-catch rate was found to be statistically significant but the differences among years was small in comparison to other factors. An examination of the influence of mitigation measures for sets made during the day in summer in the Tasmanian area showed that the level of bait thawing and unidentified factors related to individual vessels were most significant in determining the seabird by-catch rate, followed by the use of a bait throwing device. It was not possible to examine the influence of the use of bird scaring tori poles and lines as these were used during all sets examined in detail. For this data set, the amount of cloud cover had an influence, while moon phase, sea conditions and wind strength did not.

Area closures have been widely used in the management of migratory fish and conservation of endangered marine species, but very few economic models are available to assess the impacts of a closure because economists have paid little attention to complexities in fishery management, such as spatial heterogeneity in fish stocks and fleet dynamics. This study presents a spatial economic model that features (i) heterogeneously distributed stocks of multiple species, (ii) their movement across areas, (iii) travel costs depending on fishing location, and (iv) optimal allocation of fishing trips to areas and of the primary target in each fishing set. Because catch-per-unit-effort (CPUE) diminishes with effort, trips are alternately allocated to several areas, where the expected crew's wages are equalized. While this optimal allocation of trips derives a demand for labor (DDL), fishermen's tradeoff between offshore days (labor) and onshore days (leisure) yields an upward-sloping labor supply curve, which determines, together with the DDL, the equilibrium level of wage and labor. Using catch and effort data summarized from the federally mandated commercial logbooks into 5° square monthly strata, auction price data, and survey data for longliner's cost structure, this model is applied to the Hawaii longline fishery to conduct policy simulations. While a near-shore area closure leads to fewer trips of longer duration, a closure of the North Pacific to protect sea turtles significantly reduces swordfish catch and significantly increases the catch of near-shore species, which may endanger the stocks of near-shore species or affect the harvests by other boats. The impacts of prohibiting swordfish sets on the industry could be more severe than the above closure for turtle conservation. A revenue tax is not effective in reducing fishing effort. A closure increases fish movement (FM) from the closed area to open, neighboring areas, resulting in higher levels of the stocks in those open areas. This FM effect benefits the fishery industry, and could reduce the fishermen's income loss from a closure--estimated by the model without FM--by half, if fish are mobile and the closed area(s) is a "source" in terms of the direction of movement.

The economic behavior of Hawaii's longline fishers was analyzed using a cross-sectional and time-series dataset from 1991 to 1998. Three empirical essays were written analyzing (1) the technological and economic interrelationships in the longline fishery, (2) trip choice behavior, and (3) vessel entry, stay, and exit decisions of the longline fishers. Studies on the analysis of technical-economic interrelationships among species suggest that Hawaii's longline fishery is characterized by a joint production process. Substantial economic and technical interactions existed, as many of the cross-price elasticities were significant, indicating either complementary or substitution relations in production among species. There was insufficient evidence for rejecting the null hypothesis of input-output separability. Output supplies were independent of their own prices. Output elasticities to effort and stock levels were positive and significant. Fishers' trip (or fishery) choice behavior was examined by applying the utility theoretic mixed model. Fishers exhibited utility maximizing behavior by choosing the trip type that yields best return, but they appeared to be risk-averse by choosing trip alternatives with less varying return, ceteris paribus. They exhibited "inertia" in switching to an alternative trip. Stock abundance indices of major species significantly influenced the type of trip chosen. Older and smaller vessels were more likely to choose the tuna trip rather than the swordfish or the mixed trip. Finally, the vessel entry-stay-exit decision was analyzed by applying the multinomial logit (unordered) model. The probability of a vessel to stay (or exit) in the fishery increased (or decreased) for an increase in the annual earning potential of a fisher. The fleet congestion level had a significant impact on the vessel entry-stay-exit decision. Vessels were reluctant to enter to and willing to exit from the fishery for an increase in fleet size. Entry-stay-exit decision was also based on a perceived abundance in major species stock levels. A vessel was more likely to stay in the fishery when the vessel owner was a Hawaii resident or a vessel captain. Vessel age had little impact on the entry-stay-exit decision. Simulation of probabilities for both forms of choices was carried out under different fleet structure and stock conditions.

Orientador: Roberto Goitein / Banca: Alberto Ferreira de Amorim / Banca: Selene Maria Coelho Loibel / Banca: Leandro Muller Gomiero / Banca: Lucy Satiko Hashimoto Soares / Resumo: Visando contribui r para o conhecimento da dieta de peixes que habitam o ambiente pelágico do Oceano Atlântico Sudoeste, e por conseqüência compreender a rede trófica na qual estas espécies estão inseridas, foi elaborado um estudo envolvendo t rês aspectos apresentados nesta tese em forma de capítulos: (1) análise do conteúdo estomacal de Thunnus albacares, T. obesus, T. alalunga, Xiphias gladius, Isurus oxyrinchus e Alopias superciliosus; (2) uso da inferência bayesiana na análise da dieta dos predadores em questão; (3) caracterização da rede t rófica pelágica considerando as assinaturas isotópicas dos consumidores e suas presas. A coleta dos peixes foi realizada em parceria com a frota atuneira de Santos - SP, cuja área de operação compreende o mar aberto frente às regiões Sudeste e Sul do Brasil . De maneira geral, os resultados indicam que: (1) A dieta de T. albacares e T. obesus é composta primariamente por peixes teleósteos (Bramidae, Gempylidae, Trichiuridae, ent re outros), e secundariamente por moluscos Teuthida (lulas em geral ); (2) Thunnus alalunga apresentou um padrão inverso aos demais atuns anal isados, alimentando-se preferencialmente de moluscos Teuthida, deixando os peixes teleósteos em segundo plano; (3) O espadarte (Xiphias gladius) alimenta-se primariamente de lulas Ommast rephidae; (4) a alimentação de I. oxyrinchus e A. superciliosus foi dominada por cefalópodes da ordem Teuthida. Ent re os peixes, destaque para as famílias Scombridae e Trichiuridae; (5) A análise da assinatura isotópica dos predadores corroborou os padrões descri tos pela análise do conteúdo estomacal; (6) as espécies de Scombridae são presas importantes para os predadores de topo, como X. gladius e A. superciliosus. Os achados remontam a importância de pesquisas que analisem a alimentação de peixes explorados comercialmente, visto que estes estudos podem... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In order to cont ribute to the diet knowledge of fish that inhabit the pelagic environment of the southwest Atlantic Ocean, and in consequence be aware about this species insertion in the t rophic web, a study involving four distinct aspects was made up in chapters: (1) stomach content analyses of Thunnus albacares, T. obesus, T. alalunga, Xiphias gladius, Isurus oxyrinchus e Alopias superciliosus; (2) use of Bayesian inference in analyzing the diet of these predators; (3) by using the isotopic signatures of the predators, as well as their prey, to assume thei r trophic role in the system. Fish collect ions were made by collaboration of the Santos-SP tuna fishery fleet, which operates in an area comprising the open sea off the southern and southeastern Brazilian coast . In general results indicate that: (1) The T. albacares and T. obesus diet consists primarily of teleost fishes (Bramidae, Gempyl idae, Trichiuridae, among others), and secondarily of Teuthida squids; (2) Thunnus alalunga showed an opposite food composition when compared to the other tunas, feeding mainly on Teuthida squids, and teleost fish comprised a second food in importance; (3) the swordfish (Xiphias gladius) feeds mainly on the Ommast rephidae squids; (4) the food of I. oxyrinchus and A. superciliosus was dominated by cephalopods Teuthida. Among fishes, the emphasis is represented by the representatives of families Scombridae and Trichiuridae; (5) (5) The predators isotopic signature analysis corroborated the described pat terns shown by the stomach contents analyses; (6) The Scombridae species are important prey species for the top predators, such as X. gladius and A. superciliosus. The findings should help one to remember the importance of investigat ions related to fish species, which use to be important for commercial purposes, as such studies may become essential tools to be used by alternative conservation... (Complete abstract click electronic access below) / Doutor