Rockfish assessment studies on Heceta Bank, Oregon, 1980-81. Sub-project annual report: October 1, 1980 to March 1, 1982 Public Deposited

http://ir.library.oregonstate.edu/concern/technical_reports/0v838129h

"Commercial Fisheries Research and Development Act Project No. 1-151-R-2 Contract No. 81-ABD-ORAC" (from title page). 22 p.

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  • From January 1980 to January 1981 approximate monthly sampling of a unique rockfish (Scorpaenidae) fishing area on Heceta Bank, Oregon was undertaken using acoustic techniques and trawling aboard chartered commercial fishing vessels. Rankings of density of fish sign observed on acoustic transects were regressed against selected environmental variables. Acoustic abundance results showed no seasonal fluctuations nor were abundance ratings correlated to time of day. A significant correlation was obtained between rockfish abundance and feed abundance. Although regressions of acoustic estimates were significant each of the principal variables of weekly upwelling index, secchi depth, time of day, barometric pressure, feed abundance and tide fluctuations accounted for only a small part of the variance. A relationship between trawl catch rate (1b/hr) and season or time of day was not observed. Catch rates were correlated with bottom temperature, maximum tide change and tide change during the tow. Quarterly biomass estimates calculated by the area-swept method varied as much as 20-fold. We concluded that the method of ranking abundance based on acoustic signals was unsuccessful. More importantly we were unable to predict conditions during which canary rockfish (Sebastes pinniger) were available to trawlable areas.
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