ACTIVITY AND MOBILITY OF COROPHIUM VOLUTATOR - A FIELD-STUDY

The distribution of the intertidal amphipod Corophium volutator is het erogeneous at scales of cm to km. Whilst habitat preferences, interspe cific and intraspecific interactions are factors affecting patterns of heterogeneity, these are moderated by mobility. A field investigation of small-scale (cm to m) mobility was carried out on the Ythan estuar y, Aberdeenshire, during immersion and after the ebb of the tide. Obse rvations on immigration to, emigration from and activity within small areas of sediment indicated that mobility is low, but animals that do move are adult males which crawl over the sediment rather than swim. T hese individuals moved only short distances and they frequently re-use d existing burrows. This movement is probably related to reproductive behaviour. The low mobility and the short distances moved indicated th at mobility has little impact on at least large and intermediate scale heterogeneity, but shows that small-scale patterns are constantly dyn amic in time and space.