A survey of geoduck populations in the Griffith Harbour area, north Banks Island, in August 1995 / C.M. Hand and G. Dovey.: Fs97-4/2541E-PDF

"A survey of the geoduck (Panopea abrupta) population in the Griffith Harbour area on northwest Banks Island, British Columbia, was conducted by the Underwater Harvesters Association and Fisheries and Oceans Canada in August, 1995. The purpose of the survey was to estimate the density of geoducks in the general area of reported beds and to verify the location of commercial beds. Survey densities are used to calculate quotas for the geoduck fishery. A total of 48 systematically-placed transects were completed over 150 hectares of subtidal seabed in the Griffith Harbour area. Transects were post-stratified into four sites, each of which constituted a more or less continuous geoduck bed. Mean geoduck density was estimated to be 1.7/m2 , 2.8/m², 4.2/m² and 0.2/m² for Sites 1 to 4, respectively. Site 4 was excluded from calculations for overall density because it was a rocky reef and not suitable habitat for geoducks. Site 3 contained some extremely high geoduck densities, in the order of 30/m². The mean density for Site 3 excluding these extreme data was 2.4/m². Sites 1, 2 and 3 were combined to estimate overall density for use in quota calculations. The mean overall density of geoducks in Griffith Harbour beds was 2.9/m² with a 95% confidence interval of 1.9/m² - 4. 1/m². With extreme data from Site 3 excluded, the estimate was 2.2/m² (95% CI 1.6-3.0/m²). These density estimates were 61% and 22% greater than the previous estimate of 1.8/m² used to calculate quotas prior to this survey. Use of the lower density estimate is recommended for this area, and especially if survey densities are to be extrapolated to other, unsurveyed geoduck beds"--Abstract, page v.

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