Document: KEV-3-78-5

Differential settlement of the mussels Mytilus californianus and M. trossulus in sheltered on exposed and sheltered rocky shores..

ROBLES, C.D.* ¹, K.B.JOHNSON ¹ and A.MARTEL ²

California State University at Los Angeles, Los Angeles, CA 90032 USA ¹
Bamfield Marine Station, Bamfield, British Columbia, Canada ²

Abstract:
Sympatric species of adult mytilid mussels play important, but markedly different roles in wave-exposed vs. sheltered rocky shore communities. However, the relative settlement of these species in relation to wave exposure has not been examined. We set out two types of mussel spat collectors (boards covered by either nylon scrub pads or adult Mytilus californianus) on two midshore levels (7 and 9 ft. NLLW) at wave-exposed and sheltered rocky shores in Barkley Sound, British Columbia. Relative to exposed sites, very few M. californianus settled in sheltered sites, regardless of collector type; Mytilus trossulus settled in abundance in both wave exposures. These results are consistent with recent speculation about the life history "strategies" of Mytilus spp.. Contrary to another post settlement competition hypothesis, it may be the lack of M. californianus settlement that drives the relative numerical dominance of M. trossulus in sheltered areas.

Keywords: settlement, supply side ecology, mussel recruitment

This abstract is being presented at: 11:30 AM in session:
Oral Session #7: Aquatic Ecology: Shellfish to Snails.