Search

In this study, we modelled fishery observer data to compare methods of identifying community structure using cluster analyses to determine stratifications and probabilistic models for examining species co-occurrence in the Gulf of Mexico deepwater reef fish fishery. Comparing cluster analysis methods, the correlation measure of dissimilarity in combination with average agglomerative linkage was the most efficient method for determining species relationships using simulated random species as a comparison tool. Cluster analysis revealed distinct species stratifications and in combination with multiscale bootstrapping generated probabilities indicating the strength of stratifications in the fishery. A more parsimonious approach with probabilistic models was also developed to quantify pairwise species co-occurrence as random, positive, or negative based on the observed vs. expected fishing sets with co-occurrence. For the most common species captured, the probabilistic models predicted positive or negative co-occurrence between 84.2% of the pairwise combinations examined. These methods provide fishery managers tools for determining multispecies quota allocations and offer insights into other bycatch species of interest. [ABSTRACT FROM AUTHOR]

We investigated the effects of hook soak time on targeted reef species and shark bycatch in the reef fish bottom longline fishery in the Gulf of Mexico. Beginning in 2010, capture time and catch per unit effort (CPUE) for the primary target species red grouper ( Epinephelus morio ) in the fishery were evaluated using hook timers. Findings indicated that typical duration of hook soak times is longer than necessary to efficiently harvest red grouper and a reduction in gear soak times to less than one hour would result in minimal or no reduction in red grouper CPUE. The mean capture time of sharks and red grouper differed significantly, suggesting that a reduction in soak time would likely reduce the bycatch of sharks in the fishery. The study also revealed barometric pressure, lunar phase, and fish size were significant covariates with red grouper capture times and that different bait types significantly affected CPUE. Implementing shorter hook soak times would likely improve fishery profitability and potentially reduce discards of unwanted species in the fishery. [ABSTRACT FROM AUTHOR]