SUN COMPASS MIGRATION BY AURELIA-AURITA (SCYPHOZOA) - POPULATION RETENTION AND REPRODUCTION IN SAANICH INLET, BRITISH-COLUMBIA

The scyphomedusa Aurelia aurita in Saanich Inlet, a north-south orient ed fjord in British Columbia, uses a sun compass to migrate in a south easterly direction during the day. When the sky is overcast and at nig ht, A. aurita orients randomly and is dispersed passively by gentle ti dal currents. The net result is daily reaggregation of medusae into en ormous swarms along the southeastern shore of the fjord. Observations of spawning A. aurita in these swarms suggest that sun-compass migrati on and aggregative behavior may have evolved to facilitate reproductio n and to maintain the population within this fjord throughout the year .