Tidal effects on habitat selection and aggregation by juvenile pollock Pollachius virens in the rocky intertidal zone

Abstract

Nearly all the pollock population in the study area moved into the intertidal zone and alternated between aggregation in the open and dispersal in the fucoid macroalgae. On rising tides, pollock moved from the subtidal zone to the open intertidal zone in large schools then dispersed among available depths and throughout algal habitats in small schools or as solitary fish. When in algae, pollock preferred the dense algal habitat over the sparse algal habitat. On falling tides, pollock schooled in the open habitat in downshore intertidal and subtidal zones. The main seasonal difference, from early to late summer, was an overall distributional shift towards the downshore open habitat and the subtidal zone and a preference for greater depths in the intertidal zone. These results support the hypothesis that pollock were using both refuging and schooling antipredator tactics during intertidal zone migrations. -from Authors