9781888569605-ch25

Benthic Habitats and the Effects of Fishing

Symposium Abstract: Benthic Habitat in the Gulf of Alaska: Biological Communities, Geological Habitat, and Fishing Intensity

J. Heifetz, D. L. Courtney, J. T. Fujioka, H. G. Greene, P. Malecha, and R. P. Stone

doi: https://doi.org/10.47886/9781888569605.ch25

Multibeam, backscatter, and video data were collected on Portlock Bank near Kodiak, Alaska in the vicinity of groundfish fisheries. The objective was to characterize habitat in heavily fished grounds to understand whether habitats in current fishing grounds are vulnerable to ongoing fishing activities. The multibeam and backscatter data indicated at least a dozen macro- or meso-habitats. The megahabitats are the result of past glaciation and are presently being reworked into moderate (cm-m) relief features. Submarine canyons notch the upper slope and provide steep relief with alternating mud-covered and consolidated sediment exposures. The video data from the submersible Delta, indicated little evidence of trawling on the low relief grounds of the continental shelf where perhaps the level bottom did not induce door gouging and there was a lack of boulders to be turned over or dragged. The most common epifauna were crinoids, small non-burrowing sea anemones, glass sponges, stylasterid corals and brittlestars. Occasional large boulders were located in depressions were the only anomaly in the otherwise flat seafloor. These depressions may have afforded some protection to fishing gear, as the glass sponges and stylasterid corals attached to these boulders were larger than were typically observed. In contrast, there was evidence of boulders turned over or dragged by trawling in the areas of the upper slope. The uneven bottom perhaps induced gouging by the trawl doors. The substrate was mostly small boulders, cobble, and gravel. Presently there does not appear to be much habitat in this area that can be damaged by trawling. No large corals and very few large sponges were seen. Whether this is the result of past trawl activity is unclear.