Movement and activity patterns of the European lobster, Homarus gammarus, revealed by electromagnetic telemetry

European lobsters, Homarus gammarus (L.), were tracked on an artificial ree f in Poole Bay on the south coast of England using an electromagnetic telem etry system which monitored movements between reef units and recorded body movements (pitching and rolling) detected with a tilt switch incorporated i nto the transmitting tag. Several environmental variables (water temperatur e, light, hydrostatic pressure, current velocity and direction) were record ed simultaneously by the telemetry system, which was self-contained on the seabed. Movements between units of the artificial reef (excursions outside shelter) were predominantly nocturnal, peaking 1.5 to 3 h after sunset and returning to low levels shortly before dawn. A marked decline in the number of inter-reef unit movements from late summer to winter was related to dec reasing water temperature rather than to daytime light level, wave height o r tidal range. Activity indicated by the tilt switch was also greater at ni ght, but declined gradually fr-om a peak early in the night to a minimum at around midday, on average, implying a degree of activity within reef units during daylight. As with movements between reef units; activity declined s easonally with decreasing water temperature; in addition, the diel pattern of activity disappeared in winter.