Correlates of Rockfish Abundance in Howe Sound, British Columbia

Jeff Marliave, Vancouver Aquarium, jeff.marliave@vanaqua.org

Wendell Challenger, Department of Statistics & Actuarial Science, Simon Fraser University

Donna Gibbs, Vancouver Aquarium

$23,896

Baseline data for rockfish abundance, substrate associations and biodiversity were documented for newly established Rockfish Conservation Areas (RCAs) in Howe Sound during 2004-2006.  Aquarium divers explored inside and outside the first four RCAs during 2004 and 2005, counting 14,850 rockfish (primarily copper and quillback) in 184 dives.  These dives focused on the RCAs and areas outside RCAs known from previous research dives.  In 2005 a series of video transect dives was conducted.  Videotapes were scored, minute-by-minute, according to substrate type, revealing a strong association of rockfish with piled boulders as preferred habitat.  Paired divers sighted about twice as many rockfish as were documented on videotape in the same areas (same dates).  In 2006, 69 dives were randomly assigned within RCAs versus close by, but outside the government predictive model for rockfish abundance.  There was no significant difference in the probability of these random sites being occupied, inside versus outside the predicted area, but there was significantly higher abundance of rockfish in association with boulders.  Total biodiversity was documented for 127 dives, and taxon correlation with rockfish abundance related to negative association with mud substrate.  In areas of shoreline boulder habitat, wintertime hiding by copper rockfish was documented for interstitial spaces under piled boulders, a potential factor in long-term residency by rockfish in protected areas like RCAs.