MEPS 126:19-29 (1995)  -  doi:10.3354/meps126019

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

Rangeley RW, Kramer DL

Fucoid macroalgae in the rocky intertidal zone are a potentially important foraging and refuging habitat for juvenile fishes. A dominant feature of this habitat is that its availability changes with the tides. Vegetated habitat availability changes in many other systems as well, yet little is known about the effects of these changes on animal distributions. We addressed this problem by studying young-of-the-year pollock Pollachiusvirens using visual transect surveys in the rocky intertidal zone. We examined tidal effects on pollock distribution, their depth and habitat preferences and the relationship between habitat use and patterns of aggregation. Nearly all the pollock population in our study area moved into the intertidal zone and alternated between aggregation in the open and dispersal in the algae. 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. We suggest that rocky shores are important nurseries for juvenile pollock.

Habitat selection . Habitat availability . Refuging . Schooling . Marine fish nursery . Rocky intertidal zone . Pollachiusvirens . Pollock . Macroalgae . Gadidae . Visual transects

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