OBSERVATIONS OF BASKING SHARKS, CETORHINUS-MAXIMUS, IN CLAYOQUOT SOUND, BRITISH-COLUMBIA

The distribution, abundance and behavior of Basking Sharks (Cetorhinus maximus) in Clayoquot Sound, Vancouver Island, British Columbia was i nvestigated with sightings made from 1973-1999. A field study based on identification of individual sharks by photographs of dorsal fins was conducted on 23 days between June and August 1992. Sharks were sighte d in the Sydney and Shelter Inlets and Millar Channel from March to Oc tober, 1973-1992. Twenty-seven individuals were photo-identified throu gh scars, cuts or other irregularities in dorsal fins. The rate of dis covery of new sharks declined near the end of the study period suggest ing the population present in the study area is not large. Six sharks were identified on more than one occasion; duration between sightings of individuals ranged to 45 days. Observations suggest the sharks are more likely to be seen in sunny, calm weather, and in early morning or late afternoon/evening. Sharks were observed leaping from the water. Plankton tows indicated a variety of organisms, including copepods and crustacean larvae, which are likely food species. Male sharks were id entified by their claspers. Some sharks had wounds on dorsal fins appa rently caused by boat propellers. There are three records of sharks fo und entangled in fishing gear. The observations of Basking Sharks in C layoquot Sound seem to support the descriptions of seasonal appearance , discrete populations, weather dependent behavior and propensity to b ecome entangled in fishing gear described in the literature. This is t he only known aggregation of Basking Sharks remaining on Vancouver Isl and, and possibly the only one in British Columbia, and may warrant co nservation measures.