Frontiers in Marine Science (Dec 2015)
Sex biased fishing mortality and movement patterns of the dimorphic corkwing wrasse (Symphodus melops)
Abstract
Recent studies have shown that harvesting wild population may exert direct selection on growth rate independently of size, as fast growth and correlated behaviour traits may increase the probability of being captured in fisheries. Harvesting on species with sexual dimorphism in growth can therefore be selective against the faster growing sex. This hypothesis was tested in a commercial fishery of a species with males growing faster than females, the corkwing wrasse (Symphodus melops). We conducted a mark recapture experiment during the spawning period and throughout the commercial fishing season to study mortality and fine scaled movement patterns in Austevoll, Western Norway. In total, 1368 individuals were marked with passive integrated transponder tags in a protected and heavily fished area in close proximity. 293 fish were recorded captured in the commercial fishery, and fate (retained/discarded) and capture coordinates registered by onboard scientific personnel. Together with an additional 795 recaptures registered in scientific sampling, we used this dataset to estimate sex specific natural and fishing mortality and movement. We found that fishing affected nesting males more than females and female mimicking males combined; direct observed commercial capture of tagged fish was 42 % and 31 % of the respective sex classes. Both capture probability in the fishery and growth rates decreased significantly with body size for both sexes. Survival was also influenced by discard of smaller fish and selection on body size was significantly disruptive in nesting males and negatively linear in females. Our results align with expectations from the growth rate selection hypothesis and demonstrate size independent sexual differences in harvest selection in a wild population
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