Distribution and abundance of herring and other pelagic fish off the west coast of Vancouver Island in September, 1981 / by F.H.C. Taylor.: Fs97-6/1333E-PDF

"A hydroacoustic and fishing survey was carried out in September, 1981, to determine the distribution and abundance of herring off the west coast of Vancouver Island from the Juan de Fuca Trench to the Ucluth Peninsula. The major herring concentration lay along the outer edge of the continental shelf extending inshore to the Finger Bank and Southeast Corner. There were estimated to be 61,700 t in this region and on Swiftsure Bank. The largest concentration lay between Nitinat and Barkley Canyons. Only about 11% of the herring occurred south of the U.S.-Canada fishing boundary, compared to 46% in September, 1980. No schools of herring were found beyond the edge of the continental shelf. Hydroacoustic estimates in both September, 1980, and 1981 compared well with estimates derived from catch, spawn and sampling data, considering those stocks spawning on the west coast from Clayoquot Sound south and in the Strait of Georgia south of Nanaimo. In 1980-81, the catch and spawn estimate was 78,666 t, the hydroacoustic estimate 78,220 t; in 1981-82, the estimates were 67,423 t and 61,700 t, respectively. Factors affecting the reliability of hydroacoustic estimates were discussed. The major causes of bias were considered to be the estimation of target strength and the determination of the species composition of the major fish concentrations. In September, 1981, 39,600 t of hake, 13,200 t of pollock, 21,800 t of dogfish, 9,870 t of yellowtail rockfish and 8,390 t of redstripe rockfish were located. Corresponding estimates for September, 1980, were 67,230 t of hake, 31,880 t of pollock, 10,120 t of dogfish, 4,645 t of yellowtail rockfish and 3,030 t of redstripe rockfish. Differences in times of migration between the 2 years may explain the biomass differences"--Abstract, page iv.

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