Diversity and composition of catches and discards in a recreational charter fishery
A spatially and temporally stratified scientific observer program was used to examine variation in the diversity and composition of retained and discarded catches in a coastal charter-vessel line fishery. The 181 observed trips yielded 126 species and 13,357 individuals. Overall, 88 and 92 species were retained and discarded, respectively, with 34 and 38 species either solely retained or discarded. The 10 most numerous species accounted for 75% of total individuals, with 40 species encountered only once. Regional-scale differences in retained and discarded catch compositions and diversity were consistent across seasons, with species diversity being greatest in the northern region that encompassed the convergence zone of tropical and temperate waters. Within-region port-related differences in catch compositions were driven by particular species being captured in different quantities and frequencies from vessels at one port compared to the other, and together with the high level of trip-to-trip variation in catches, were the result of localised and often vessel-specific differences in fishing practices, grounds and habitats fished, and client/operator preferences. Habitat-related differences in catch compositions were greatest between bare sand and structured reef and reef/gravel substrata. Discarding patterns varied among regions, with 25–52% of individuals with a prescribed legal length limit, and 14–72% of individuals with no length limit, being discarded. Discarding was due to a combination of compliance with length-based and no-take regulations, as well as client and operator preferences for particular species and sizes, and not the result of catch quotas. The results show that assessments and management of charter fisheries need to consider the human dimensions, as well as the ecological, aspects of catch variation.