Living Substrate in Alaska: Distribution, Abundance, and Species Associations
Patrick W. Malecha, Robert P. Stone, and Jonathan Heifetz
Abstract. “Living substrate” has been identified as an important marine habitat and is susceptible to impacts from fishing activities. In Alaskan waters of the North Pacific and Bering Sea, little is known about the distribution of deepwater living substrate such as sponges (phylum Porifera), sea anemones (order Actiniaria), sea whips and sea pens (order Pennatulacea), ascidians (class Ascidiacea), and bryozoans (phylum Ectoprocta). Based on 26 years of survey data (mostly from catches in bottom trawls collected between 1975 and 2000), we created living substrate distribution maps. In general, the five groups of living substrate were observed in varying densities along the continental shelf and upper continental slope. Catch per unit effort (CPUE) of sponges was greatest along the Aleutian Islands, while CPUEs of ascidians and bryozoans were greatest in the Bering Sea. Large CPUEs of sea anemones, sea pens, and sea whips were observed in both the Bering Sea and the Gulf of Alaska. Broad-scale species associations between living substrate and commercially important fishes and crabs were also identified. Flatfish (Bothidae and Pleuronectidae) were most commonly associated with ascidians and bryozoans; gadids (Gadidae; also known as cods) with sea anemones, sea pens, and sea whips; rockfish (Sebastes spp. and shortspine thornyhead Sebastolobus alascanus) and Atka mackerel Pleurogrammus monopterygius with sponges; crabs (Chionoecetes spp., Paralithodes spp., Lithodes spp., Dungeness crab Cancer magister, and hair crab Erimacrus isenbeckii) with ascidians; and other commercial fish species (sablefish Anoplopoma fimbria, Hexagrammidae, and Rajidae) with sea pens and sea whips. These data should provide resource managers with insight into living substrate distribution and relationships among benthic community organisms and, ultimately, with future in-depth studies, may aid in determining specific areas for habitat protection and facilitate management practices that minimize fishery impacts to living substrate.