0304 Deep sea coral distribution and habitat in the Aleutian Archipelago

Habitat mapping of seventeen sites covering 2,600 km2 at depths of 30 – 3,800 m coupled with visual observations to 2,950 m were used to collect biological information and develop predictive models that relate coral and sponge distribution to environmental characteristics. Habitats dominated by bedrock and cobble supported the highest densities of corals. Diversity of corals and sponges increased from deep to shallow water.

For the predictive model, explanatory variables included depth, slope, and rugosity with depth and slope being the most important factors. Models of coral and sponge presence/absence north of the Aleutian Islands Archipelago were more successful than models south of the Archipelago. The most damage and disturbance to coral and sponge communities occurred at depths < 800 m which generally corresponded to the depth limit of the majority of fisheries that use bottom contact gear.

There was a consistent positive relationship between damage and disturbance levels and intensity of bottom trawling, whereas results varied for other gear types. Some commercial fish and crab species aggregate in habitats where corals are abundant, making these habitats at risk to fishing gear impacts.

Protective measures implemented in the Aleutian Islands include restricting bottom trawling to historically fished areas. While this protective measure may halt the expansion of bottom trawling to areas not fished, the conservation of coral and sponge habitat in fished areas is still of primary concern.