USE OF ROCKY INTERTIDAL HABITATS BY JUVENILE POLLOCK POLLACHIUS-VIRENS

We investigated patterns of distribution and foraging by young-of-the- year pollock Pollachius virens in the rocky intertidal zone. Pollock w ere sampled by beach seine in fucoid macroalgae and in open habitats a t all stages of the tide, day and night throughout the summer. Their p resence in shallow water at the high tidal stages indicated that at le ast part of the pollock population migrated across the full width of t he intertidal zone (150 m) each tide. Densities in shallow water were much higher at low than at high tidal stages suggesting that a large i nflux of pollock moved in from the subtidal zone at low tidal stages a nd then dispersed into intertidal habitats at high tidal stages. There were few differences in pollock densities between algal and open habi tats but abundances likely increased in the algal habitat at higher ti dal stages when changes in habitat availability are taken into account . Densities were higher at night and there was an order of magnitude d ecline in pollock densities from early to late summer. In another stud y we showed that piscivorous birds are a probable cause of pollock sum mer mortality. Pollock fed on invertebrates from intertidal algae rela tively continuously. The tidal migrations of juvenile pollock observed in this study and their use of macroalgae as a foraging and possibly a refuging habitat strongly suggests that the rocky intertidal zone ma y be an important fish nursery area.