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

The U.S. pelagic longline fishery catches 98% of domestic swordfish landings but is also one of the three fisheries most affecting federally protected sea turtles (Crowder and Myers 2001, Witherington et al 2009). Bycatch by fisheries is considered the main anthropogenic threat to sea turtles (NRC 1990). Accurate and precise bycatch estimates are imperative for sea turtle conservation and appropriate fishery management. However, estimation is complicated by only 8% observer coverage of fishing and data that are hierarchical in structure (i.e., multiple sets per trip), zero-heavy (i.e., bycatch is rare), and often overdispersed (i.e., larger variance than expected). Therefore, I evaluated two predominant bycatch estimation methods, the delta-lognormal method and generalized linear models, and investigated improvements in uncertainty incorporation. I constructed a simulation model to evaluate bycatch estimation at two spatial scales under ten spatial models of sea turtle, fishing set, and observer distributions. Results indicated that distributing observers relative to fishing effort and using the delta-lognormal-strata method was most appropriate. The delta-lognormal-strata 95% confidence interval (CI) was wider than statistically appropriate. The delta-lognormal-all sets pooled 95% CI was narrower but simulated bycatch was above the CI too frequently. Thus, I developed a bycatch estimate risk distribution to incorporate uncertainty in bycatch estimates. It gives managers access to the entire distribution of bycatch estimates and their choice of any risk level. Results support the management agency's observer distribution and estimation method but suggest a new procedure to incorporate uncertainty. This study is also informative for many similar datasets. / Master of Science

Made available in DSpace on 2014-06-11T19:35:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-12-20Bitstream added on 2014-06-13T19:46:45Z : No. of bitstreams: 1 gorni_gr_dr_rcla.pdf: 816053 bytes, checksum: 87b337f265397de37595051222587ecc (MD5) / 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... / 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)

Tuna longline fishery produces the highest output among Taiwanese far sea fisheries. In 2007, it created NT$31.7 billion of sales, 1/3 of Taiwanese fisheries. In 2005, ICCAT identified Taiwanese tuna longliners because of their excessive catches and laundering activities in bigeye tuna. The identification by ICCAT initiated dramatic change of Taiwanese tuna longline fishery. This study described the characters of Taiwanese tuna longline fishery, compared catches of 4 major tuna longline countries: Taiwan, Japan, South Korea and China in 2004. The result showed that Taiwanese tuna longliners got the highest catches. In addition, Taiwanese boat owners owned and operated longliners in other flags. The huge fishing capacity which owned by Taiwanese boat owners became a threat to tuna resources. This study first analyzed the attributes of diamond of national advantage that help Taiwanese tuna longline fishery prospect in Cianjhen Fishing Port, Kaohsiung City, and how it enjoyed the benefit of industry cluster. This part depicted success of the past. Facing the global over capacity of fishing vessels and shrinkage of tuna resources, Taiwanese tuna fishery can not indulge in glory of past. Instead, disadvantage of competition condition highlighted importance of end-game strategy which help boat owners make their decision of continuation or divestment of their business. The decline of an industry derives from the weakness of itself. This study emphasizes organization change and innovation, which must be rooted from respect to the precious tuna resources, then apply fishery science to improve fishing efficiency and proper use of manpower from different nations.