Meeting Abstract

77.5  Friday, Jan. 6  Lingcod and rockfish impacts on benthic community structure TURNER, KR*; SEBENS, KP; Univ. of Washington; Univ. of Washington

Management decisions affect not just the species targeted by management, but also unharvested species related to those target species through ecological networks. Removal of top predators from subtidal communities releases prey species from predation, allowing prey populations to increase. Examples from around the world have shown that impacts from predator removals can cascade to harvestable species at lower trophic levels. Predator removals can also significantly change the composition of the entire marine community. We are studying the effects of large carnivorous fishes (lingcod, Ophiodon elongatus, and rockfishes, Sebastes spp.) on the rocky subtidal communities of San Juan Channel. Predatory fish abundance is variable within San Juan Channel, in part due to marine protected areas, which allows us to study community structure across a range of predator abundance. We use surveys of all trophic levels in this system, combined with exclusion cages designed to restrict fish access from large swaths of the benthos, to determine the community-wide impacts of predatory bottom fishes. Our preliminary results show that predator abundance does vary across San Juan Channel sites, as do species at lower trophic levels. However, correlations between predators and other trophic levels are not consistent at all sites. We have also examined the diets of two species of rockfishes to aid in the construction of a food web for this subtidal community. Our non-lethal analysis of the diet of copper rockfish (S. caurinus) demonstrates close agreement with the findings from previous studies, although the individuals in our study were less reliant on fish prey. The results from this research may be used to support ecosystem-based management goals by informing fisheries managers about the potential community-wide impacts of recovering bottomfish populations.