The intent of convening the international symposium on circle hooks in research, management, and conservation was to yield a contemporary, sciencebased assessment of the management and conservation utility of circle hooks in commercial, recreational, and artisanal fisheries around the globe. The symposium objective was to provide a forum for individuals, organizations, and agencies to share relevant research results and perspectives. Based on the presentations, an examination of the literature, and the collective experience and knowledge of the authors, we provide a brief overview of the current status of circle hook research along with a list of research needs, with a particular focus on science that has the potential to inform managers and stakeholders. progress was made on the definition of a "true circle hook." There was strong recognition that circle hooks represent just one of the tools available to managers for reducing bycatch and release mortality. also defined was the need for an integrative approach that considers strategies that complement the use of circle hooks. some of the research needs identified include a greater emphasis on human dimension studies to identify those factors that may impede adoption of circle hook technology by stakeholders and comparative studies of circle hook performance relative to mouth morphology, dentition, and feeding behavior. While the literature on effective use of circle hooks is growing, there remains a number of unanswered questions that will require study before circle hooks are more widely adopted for conservation and management of aquatic living resources.
-The curve used until recently by the International Commission for the Conservation of Atlantic Tunas (ICCAT) to represent the growth of western Atlantic bluefin tuna, Thunnus thynnus, was estimated using tagging information and modal sizes that corresponded primarily to very young fish (ages 1-3, primarily). The estimated maximum average size from this curve is very large (382 cm), which could be a result of the scarcity of large bluefin in the data used. Recently, scientists have developed techniques for reading ages from bluefin ear bones (otoliths); the accuracy of the age readings has been validated with bomb radiocarbon dating. These age readings are primarily for large bluefin (ages 5 and older), and indicate slower growth and older ages than was previously assumed. However, an analysis of these data resulted in growth curves that predicted very small mean sizes for the youngest age group, which could be a result of the lack of small fish in the data used. In this study, we combine the otolith-based age readings with the size frequency distributions of small (ages 1-3) bluefin caught by purse seiners in the 1970s where the age groups are distinctly statistically as well as visible to the eye. We analyzed the two datasets jointly using a maximum likelihood approach and assumed that variability in length-at-age increases with age. The resulting growth curve predicts sizes at young and old ages that are very consistent with observed data such as the maximum sizes observed in the catch and the modal sizes for very young bluefin. The resulting curve is also very similar to the curve used by ICCAT for eastern Atlantic and Mediterranean bluefin.
We developed an efficient sampling design-based approach using fishery-independent surveys to estimate population abundance of pink shrimp Penaeus duorarum over time in Biscayne Bay, Florida. We initially implemented quarterly stratified random sampling (StRS) using nine habitat strata and determined that average pink shrimp density (numbers/m 2 ) was highest in late fall and lowest in spring and late summer. Coefficient of variation of the quarterly surveys, expressed as percent standard error/mean density, ranged from 5.8% to 14.3%. We found StRS to be more efficient (i.e., with lower variance) than simple random sampling (SRS) in most seasons. Statistical analyses suggested that pink shrimp densities were dependent on the biophysical habitat variables of bottom substrate, depth, and salinity. We also noted ontogenetic shifts in these relationships that were particularly pronounced at the onset of sexual maturation. Poststratification analysis was used to further evaluate several alternative habitat-based sampling schemes. Results showed that a five-strata composite design that used all three habitat variables was similar in performance, but less complex, than the original nine-strata design. In addition, the composite design outperformed both SRS and all other StRS designs indexed on single habitat variables. The new five-strata composite design was implemented in late summer 1997 and achieved a significant reduction in coefficient of variation compared with the late summer 1996 survey. This new design did not perform as well as expected in late fall 1997, which we attribute to a mismatch between our seasonal sample allocation strategy and the timing of pink shrimp recruitment into Biscayne Bay in 1997. Finally, we show how statistical sampling designs that use stratifications based on relevant habitat covariates can yield high-precision abundance estimates at low costs and provide a robust quantitative methodology for identifying habitat essential to fisheries production.
-Ecological risk assessment is a useful methodology for assisting the management of fisheries from an ecosystem perspective. Atlantic tuna fisheries, managed by the International Commission for the Conservation of Atlantic Tunas (ICCAT), are economically important and interact with several bycatch species. In spite of these interactions, no comprehensive ecological risk assessment has been conducted for bycatch species caught in ICCAT fisheries. In this paper, we followed a two stage approach with the objective of assessing the relative risk of species being negatively impacted by Atlantic tuna fisheries. An analysis of the ICCAT bycatch species list (which includes all species reported to have interacted with different tuna fishing gears operating in the Atlantic) revealed that most of these species are caught in longline fisheries, followed by gillnets and purse seines. According to the IUCN red list, 7 species of the ICCAT bycatch list (3 coastal sharks, 3 sea turtles and one seabird) are categorized as critically endangered. In our study, and based on their life history characteristics, marine mammals and coastal sharks caught in ICCAT fisheries showed the highest intrinsic vulnerability values. A productivity susceptibility analysis for the European Union (EU) tropical tuna purse seine fleet and the United States (US) pelagic longline fleet revealed two groups with high relative risk scores. The first one included pelagic and coastal sharks, characterized by relatively low productivities, and the second one included teleosts, characterized by higher productivities but high susceptibility to purse seine and longline gears. Some alternative approaches to conduct productivity susceptibility analyses in the context of ecological risk assessments are discussed.
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