Technical Report
 

Groundfish surveys on the continental shelf off Oregon, 1971-74

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https://ir.library.oregonstate.edu/concern/technical_reports/2801ph13c

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  • This report summarizes information obtained from groundfish surveys conducted by the Oregon Department of Fish and Wildlife from 1971 through 1974. The program was a comprehensive marine resource survey of the continental shelf and upper continental slope off Oregon between the Columbia River and Cape Blanco. Major goals were: (1) to obtain estimates of abundance or biomass for groundfish with emphasis on flatfish; (2) to develop ways of indexing year class (brood year) strength of flatfishes important to the commercial trawl fishery before they enter the fishery; and (3) to obtain estimates of age, growth and mortality rates of important flatfish. Such information, coupled with estimates of exploitation and fishing rates, provide a basis for estimating optimal levels of yield or catch. Emphasis of the surveys was on flatfish because they were very important to the Oregon trawl fishery om 1971-75 and since the early 1940’s. An additional reason for our stressing work on flatfish was that in the initial planning, it was hoped that the National Marine Fisheries Service (N.M.F.S.) might do the offshore work, especially on rockfish. However, since this did not occur, the surveys were extended seaward to include the upper continental slope in 1973-74. Surveys provide information which is difficult to obtain from commercial fishery landing statistics. For example, it is difficult to obtain estimates of recruitment on the abundance of juveniles, because commercial trawls have larger mesh size and draggers also discard at sea the small and unmarketable fish; thus the data obtained are not influenced by market conditions, size limits or the economic need to fish mostly in areas of high abundance which commercial boats face. Simply put, survey trawl sets give a clearer picture of what comes up in the net. The purpose of this report is to present the results obtained from the analysis of a great mass of data, obtained not only from the surveys, but also from landing statistics and fishermen’s logbooks.
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file details demory.1976.or_groundfish_surveys_on_the_cont_shelf_71-74_ir76-9.pdf 07/11/2017 Público
file details demory.1976.or_groundfish_surveys_on_the_cont_shelf_71-74_ir76-9.pdf 07/11/2017 Público