The effects of size-selective fishing pressure on the mating system, population structure, and sex-change dynamics of the California sheephead, Semicossyphus pulcher


Lynne Wetmore

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The California sheephead Semicossyphus pulcher is a hermaphroditic wrasse which presents an interesting challenge in environmental management due to its harem mating system and protogynous life history pattern. The fishery for California sheephead is size-selective, and while the recreational fishery has historically targeted larger males, the more recent live-fin fishery specifically targets small immature females for the restaurant trade. It is uncertain whether these practices affect the timing of sexual changeover or alter the natural harem mating system. In this study, California sheephead populations were surveyed at eleven sites with varying degrees of fishing pressure, and fish were collected for age and growth analysis. Five mainland sites, two Santa Catalina Island sites and two Santa Barbara Island sites were sampled in 2005-2006. Transect data collected at these sites suggests that while population density may be a function of geographic location and habitat type, mean fish size and sex distribution may be affected more acutely by anthropogenic influences such as fishing pressure. It is possible that such size selective effects may reduce the overall fecundity of the population, thus threatening the sustainability of the fishery stock


Dan Pondella




Norris Scholars Program

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