ECOLOGICAL DATA
Distribution: occurs in sheltered coastal areas; less
abundant in north than Tresus capax.
Habitat: sandy substrates; common in eelgrass beds; burrows to 1 m, but
generally deeper than Tresus capax; planktonic larvae dispersed by currents; adults
remain in same burrow for life.
Tidal elevation: lower one third of intertidal zone to 20 m subtidal depth.
Food: suspension feeder; feeds on planktonic organisms and detritus.
Predators: birds, moon snail, sea stars, crabs, and fishes.
GROWTH RATE
Fairly rapid; sexually mature at 60 mm, after 3 yr; reach 100
mm after 5 yr in Strait of Georgia and 6 yr in Queen Charlotte Strait; large adults (20
cm) can weigh up to 1.8 kg.
FISHERY
Small commercial, Native and sport fisheries; 1986 total horse
clam commercial harvest was 96 t valued at $63,00 in 1986; sewage pollution and paralytic
shellfish poisoning (PSP) have closed some coastal areas to harvesting.
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REFERENCES
Bernard, F.R. 1983. Catalogue of the living bivalvia of the
eastern Pacific Ocean: Bering Strait to Cape Horn. Can. Spec. Publ. Fish. Aquat. Sci. 61:
40.
Bourne, N. 1986. Intertidal clams, p. 22-31. In G.S. Jamieson and K. Francis
[ed.] Invertebrate and marine plant resources of British Columbia. Can. Spec. Publ. Fish.
Aquat. Sci. 91.
Cheney, D.P., and T.F. Mumford, Jr. 1986. Shellfish and seaweed harvests of Puget
Sound. Wash. Sea Grant Program, Wash. Univ. Press, Seattle: 164 p.
Jamieson, G.S. 1986. Paralytic shellfish poisoning, p. 44-46. In G.S. Jamieson
and K. Francis [ed.] Invertebrate and marine plant resources of British Columbia. Can.
Spec. Publ. Fish. Aquat. Sci. 91.
Kozloff, E.N. 1983. Seashore life of the northern Pacific coast. Douglas &
McIntyre, Vancouver: 289.
Quayle, D.B. 1978. The intertidal bivalves of British Columbia. B.C. Prov. Mus. Handb.
17: 63-64.
Quayle, D.B., and N. Bourne. 1972. The clam fisheries of British Columbia. Fish. Res.
Board Can. Bull. 179: 70 p.
Ricketts, E.F., J. Calvin, and J.W. Hedgpeth. 1985. Between Pacific tides. 5th ed.
Stanford Univ. Press, Stanford, Calif.: 376-378.
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