Depth and Habitat Distribution of Parastichopus californicus Near Sitka, Alaska

Woodby, D; Smiley, S; Larson, R

The depth distribution of sea cucumbers Parastichopus californicus was investigated in the vicinity of Sitka Sound, Alaska, to evaluate the proportion of the emergent population available to commercial dive harvesters. A submersible was used to census 20 transects to 118 m. Observations above 10-m depth were made by scuba on 10 transects. Sea cucumber densities were greatest in shallow waters, with approximately 60% of the sea cucumbers observed above 15 m and 70% above 20 m. Average densities were 0.03•m-2 on the submersible transects and 0.30•m-2 on the scuba transects. The deepest sea cucumber observed was at 87 m. Sea cucumber densities were highest on shell debris and gravel (pebbles), and lowest on mud and silt bottoms. Tests for substrate distribution generally indicated a nonrandom affinity for harder substrates, except bedrock and boulders. The mostly shallow distribution of P. californicus near Sitka exposes approximately two-thirds of the surveyed population to exploitation by commercial divers, who commonly descend to 15- or 20-m depth. The large fraction of the population in deeper water is not included in estimating the harvestable surplus, and because this leads to an underestimate of the population size, this approach provides a conservative safeguard against overexploitation.

Depth and Habitat Distribution of Parastichopus californicus Near Sitka, Alaska

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