Meeting Abstract
Pisaster ochraceus (ochre sea star) is a major motile predator often found in rocky intertidal zones along the Pacific coast of North America. Commonly referred to as a keystone predator, P. ochraceus plays a significant role in shaping the structure of intertidal communities. During low tide, P. ochraceus are commonly found occupying shaded, damp crevice microhabitats in the intertidal zone to avoid adverse abiotic and biotic conditions, such as intense sunlight and predation by gulls. To better understand the behavior of these predators, we examined their diet and movement in-situ on San Juan Island, WA. Diet was monitored in the summers of 2018 and 2019 by turning over all individual stars within a fixed plot and noting the presence and identity of prey. Movement was tracked using time lapse photography collected in July 2019. Despite the crevices being nearly devoid of food, P. ochraceus spent much of their time inside crevices, where they moved the slowest, if at all. When submerged underwater during high tide, they moved outside the crevice, where prey is more abundant, exhibiting the fastest movement along the crevice edge. Our results support the idea of a feeding vs refuge tradeoff, wherein the abiotic stressors outside of the crevice exceed the sea star’s need to feed. Although this predator can exert a major effect on the local prey community, their ability to forage and exert said community effect is limited by the abiotic conditions of their habitat.
