THE BASKING SHARK CETORHINUS-MAXIMUS (GUNNERUS) IN IRISH WATERS - PATTERNS OF DISTRIBUTION AND ABUNDANCE

A sighting scheme was established during 1993 to determine the distrib ution and abundance of the basking shark in Irish waters. One hundred and forty-two sighting records were made of 425 individuals during 199 3. Sightings were received from around the entire Irish coast, but con centrations were evident off the east, south-west and northern coasts. Sightings were made between April and November, but peaked in June an d September. Although group size varied from one to twenty animals, mo st records were of single animals. Most sharks were between 4m and 6m in length, with only one under 2m. Twenty-eight records were of baskin g sharks entangled in fishing nets, usually surface gill-nets, and spe cimens were reported washed up on all coasts. A database, including hi storic records made before 1993, was established. When compared with h istorical accounts of basking sharks in Irish waters, the present stud y suggests that sharks are scarce in areas in which they were once fis hed and are now more abundant at other locations. They are appearing l ater in the year than previously reported. Surface sightings were corr elated with sea surface temperatures, with a temperature of 11.5-degre es-C being critical. Basking sharks appeared later along the north coa st than along the south, and this was attributed to the timing of the spring plankton bloom in coastal waters.