Exploratory fishing and hydroacoustic observations of rockfish off Brooks Peninsula, Vancouver Island, from the MV Velma C and CSS John P. Tully, March 13-23, 1989 / by K.R. Matthews, J.R. Candy, L.J.... : Fs97-4/2029E-PDF

"This report summarizes cruise results from two vessels operating in Brooks Bay, on the west coast of Vancouver Island, between March 13-23, 1989. The purpose of the joint survey was to describe rockfish communities on hard (untrawlable) bottom, and to compare these communities with similar communities on smooth (trawlable) bottom. In order to fish hard-bottom areas, the MV VELMA C, a chartered commercial longline vessel, deployed and retrieved sunken gillnets. Fishing was conducted in four habitat types identified by concurrent hydroacoustic observations from the CSS JOHN P. TULLY. These were: (1) smooth-bottom habitat generally within 100-200 m, (2) rough-bottom pinnacles with vertical relief of 10-20 m typically found between 95-130 m, (3) smooth plateaus adjacent to the shelf dropoff deeper than 170 m, and (4) the shelf dropoff at about 170-200 m. The distribution, diet behaviour, and biomass of fish schools in these areas was determined hydroacoustically. During the day, fish tended to concentrate near the bottom, and they became more dispersed at night. Transitions between night and day configurations occurred within 0.5 h. At least two types of fish schools were identified from echograms, one over rough-bottom pinnacles, and the second at the shelf dropoff. Catches of 55.3-78.5 fish/set and 5.3-8.3 species/set were obtained on pinnacles and deeper areas adjacent to the shelf dropoff, whereas the lowest catches (mean 23.3 fish/set and 2.3 species/set) were obtained on smooth-bottom areas. The catch was dominated by four species: lingcod Ophiodon elongatus (23.4%), bocaccio Sebastes paucispinis (18.7%), yellowtail rockfish S. flavidus (15.9%), and canary rockfish S. pinniger (15.5%)"--Abstract, page iii.

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