Bottom trawl and exploratory hydroacoustic survey for rockfish in Queen Charlotte Sound, June 20 to July 7, 1994 / by C.M. Hand, G.D. Workman, L.J. Richards, R. Kieser and R.I. Perry.: Fs97-4/2300E-PDF

"A joint trawl/hydroacoustic survey of rockfish stocks in Goose Island Gully, Queen Charlotte Sound, was conducted by the M/V OCEAN SELECTOR and the R/V W.E. RICKER from June 20 to July 7, 1994. The purpose of this survey was to update the time series of biomass estimates of Pacific ocean perch from standard trawl surveys, to investigate the potential for hydroacoustic techniques, to measure rockfish abundance, and to collect oceanographic information to explore the relationship between rockfish and their environment. The trawl survey followed the stratified-systematic approach of previous surveys and produced a Pacific ocean perch relative biomass estimate of 16,100 t. The previous two-vessel survey in 1984 had produced Pacific ocean perch relative biomass estimates of 13,700 t and 7,600 t. Because different vessels participated in these surveys, a vessel effect and/or a true abundance increase could account for the higher measured abundance in 1994. Echograms compiled during the 1994 hydroacoustic survey were composed of distinctive structures which could be interpreted as species categories. However, Pacific ocean perch could not be reliably identified. The acoustic biomass estimate of all fish from depths where rockfish dominate (180 to 300 m) was 15,600 t, based on a fish target strength of -35 dB/kg. Acoustic detection was limited, however, to approximately 14 m above the bottom. Therefore, an unknown quantity of near and on-bottom fish were undetected"--Abstract, page iii.

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