. The Canadian field-naturalist. 1994 Darling and Keogh: Basking Shaks in Clayoquot Sound 201. LEGEND "4" DATES SHARKS SIGHTED D SHARKS SIGHTED | SHARK SIGHTED AND PHOTO-ID AUGUST Figure 3. Survey effort in 1992. On 2 and 4 July sharks were sought but not sighted. camped in the region a watch was kept on the water throughout the day. The area was surveyed in 5-6 m boats. When a shark was sighted the time and location were record- ed, and the animal was approached to obtain pho- tographs of both sides of the dorsal fin whenever possible. Occasionally, a color sonar system was used to
. The Canadian field-naturalist. 1994 Darling and Keogh: Basking Shaks in Clayoquot Sound 201. LEGEND "4" DATES SHARKS SIGHTED D SHARKS SIGHTED | SHARK SIGHTED AND PHOTO-ID AUGUST Figure 3. Survey effort in 1992. On 2 and 4 July sharks were sought but not sighted. camped in the region a watch was kept on the water throughout the day. The area was surveyed in 5-6 m boats. When a shark was sighted the time and location were record- ed, and the animal was approached to obtain pho- tographs of both sides of the dorsal fin whenever possible. Occasionally, a color sonar system was used to determine the depth of the scattering layer in the study area. Ocean surface temperature readings were obtained from a salmon farm within 1 km of the study site. Photographic identification Identification of individual animals using pho- tographs of the irregularities in dorsal fins is a well- tested technique used in the study of wild whales and dolphins (, Bigg et al. 1987). Photo-identification enables repeat sightings of individuals which, in turn, allows the determination of abundance estimates, length of stay, movements, site-fidelity, and associa- tions between individuals. The feasibility of using this technique for the study of Basking Sharks was tested by photographing both sides of the dorsal fin. Ilford black and white film, pushed to 1600 ASA, and a shutter speed of 1000th of a second, and Kodachrome 64 film were used. The photographs were processed and compared to determine identifiable individuals. Results Sightings and distribution Basking Shark sightings documented by a local commercial pilot, Doug Banks, from 1973-1992* are given in Table 1. Other sightings recorded prior to the study period are given in Table 2. These sight- ings indicate the long-time presence of sharks in the region, and extend the documented range of sharks beyond the 1992 sightings. Figure 1 indicates sight- ings made outside the primary 1992 study area. The majority of sightings cent
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