Distribution and abundance of haliotis kamtschatkana in relation to habitat, competitors and predators in the Broken Group Islands, Pacific RIM National Park reserve of Canada

Baseline information on the distribution and abundance of Haliotis kamtschatkana was obtained throughout the Broken Group Islands (BGI) in shallow- (2-5 m) and deep-water (6-9 m) habitats. The study demonstrates that abundance of northern (pinto) abalone varied spatially throughout the area and with depth. The shallow habitats in the study area supported significantly higher densities (0.18 abalone/m(2) +/- 0.02 SE) of northern abalone when compared with deep habitats (0.10 abalone/m(2) +/- 0.02 SE). Maximum and minimum sizes of northern abalone measured in BGI were 132 and 4 mm shell length (SL), respectively. There were significant differences in abalone SL among the 5 island groups and the 2 depth zones. Juvenile abalones were more abundant in the deep habitat than in the shallow habitat. A significant correlation was detected between abalone densities and the relative index of exposure. There was a positive correlation between abalone size and the abundance of benthic macroalgae and an inverse relationship between abalone size and the abundance of red sea urchins (Strongylocentrotus franciscanus). A positive correlation between abalone and red sea urchin densities was observed. Seven percent of juvenile abalone (less than or equal to45 mm SL) was found under the red sea urchins' spine canopy. Distribution and abundance of selected invertebrate species associated with northern abalone including its known predators (ie, sea stars, crabs, octopuses) were assessed. The abundance of northern abalone was inversely correlated with predator abundance and density of benthic macroalgae. Detailed surveys of associated organisms and substrate types suggest that the distribution and abundance of northern abalone is a complex function of community interactions and substrate habitat characteristics.