ACTIVITY AND TRAPPING CHARACTERISTICS IN THE FIELD OF ORCHOMENE NANUS(KROYER) (AMPHIPODA, LYSIANASSOIDEA) AT MILLPORT, SCOTLAND

The scavenging lysianassoid Orchomene nanus virtually monopolized catc hes of amphipods taken in baited traps (using crushed shore crabs Carc inus maenas as bait) deployed in shallow water (5-6 m). Only traps dep loyed overnight attracted O. nanus. Activity was not associated with a ny particular time of night. Differences in sub-surface temperature co rrelated significantly with variation in nightly catch rate (data for May), but this may not reflect a direct causal relationship. A lunar c ycle of activity, however, was implicated in May. Trap retention effic iency proved to be high. There was an exponential decline in catch rat e with trap elevation above the sea bed. Seasonal variation in catch r ate was apparent, with highest catches in late autumn, correlating sig nificantly with seasonal variation in water temperature. Neither the s easonal variation in the duration of darkness, nor the position of the sample day in the lunar cycle influenced seasonal catches significant ly.