Noncommercial benthic fauna

Eastern Bering Sea



Phylum Mollusca, class Bivalvia

Species Representatives: Some of the more abundant large bivalves in the SE Bering Sea are: Patinopecten caurinus, Mytilus trossulus, Clinocardium ciliatum, Macoma calcarea, Serripes groenlandicus, Mactromeris polynema, and Hiatella arctica.

Distribution and Life History: Bivalve mollusks are among the dominant benthic infauna of the SE Bering Sea. One hundred and twenty-eight species have been found in the area (McDonald et al., 1981). Because most species are small, the trawl survey catch of dead bivalve shell bears little resemblance to the distribution, shell size, and species composition of most of the live bivalve community. Some of the largest SE Bering Sea bivalves are Patinopecten caurinus (to 30 cm), Modiolus modiolus (to 15 cm), Serripes groenlandicus (to 13 cm), Mactromeris polynyma (to 14 cm), and Panomya arctica (to 18 cm) (Kessler, 1985). Only the collective weight of bivalve shell and shell fragment is recorded on SE Bering Sea trawl survey stations. Shell with large sessile invertebrates attached is weighed and counted with other specimens of that invertebrate species. If several large species are attached to a shell, the species are separated, but the shell usually remains with one of the species. The category "empty bivalve shell" is largely shell without attached invertebrates.

Bivalve shell is important both as cover for motile (free-living) organisms, and attachment substrate for sessile (attached) organisms. Over much of the SE Bering Sea shelf, dead shell probably provides a significant proportion of habitat for invertebrates requiring hard surface for attachment. Many snails lay their egg capsules on shell. Concentrations of bivalve and gastropod shell and shell fragments are called shell hash. Shell hash, consisting mostly of bivalve shell, was the most important epibenthic substrate for juvenile blue king crab, Paralithodes platypus, in the Pribilof Islands area (Armstrong et al., 1985). Shells of this type were generally intact or in large pieces, and were usually covered with a profuse growth that included bryozoans, barnacles, anemones, and ascidians.