TIDAL, DIEL AND LONGER TERM CHANGES IN THE DISTRIBUTION OF FISHES ON A SCOTTISH SANDY BEACH

Fishes were sampled by seine and beam trawl over tidal and diel cycles on a sandy beach on the west coast of Scotland in June and August. Sp ecies composition of the catches of the 2 gear types differed. There w as a significant positive relationship between depth (0 to 5 m) and sp ecies richness but a few species were restricted to depths of <5 m. Al though significantly more species and individuals were caught at night and at low tide there was no evidence for the existence of distinct ' day' and 'night' communities. Differences between catches at high and low water were caused by the movement of a few species into the intert idal zone on the rising tide. Diel differences in abundance were princ ipally due to an inshore migration of several species of gadoids at du sk and movement offshore at dawn. Longer term changes in abundance and distribution were attributed to predation and movement into deeper wa ter.