Will the introduced mussel Mytilus galloprovincialis outcompete the native mussel M. trossulus in Puget Sound? A study of relative survival and growth rates among different habitats

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Proceedings of the Puget Sound Georgia Basin Conference, Seattle, 2005




The Mediterranean mussel (Mytilus galloprovincialis = Mg) has become established throughout Puget Sound and the effects of this species introduction on the native mussel M. trossulus (Mt) are unknown. Mg and hybrids between Mg and Mt (Mgt) are abundant on floating docks and large Mg and Mgt mussels also occur at low frequencies in the intertidal zone and in areas of low salinity. A variety of factors (e.g., growth/survival rates, predation, larval recruitment) may be causing these observed distribution patterns. In this study we performed three field experiments to examine the relative survival and growth rates of Mg and Mt: 1) at different tide heights on pilings vs subtidal locations on docks, 2) when grown in single-species groups and mixed-species groups, and 3) at locations with different salinities. Individuals of Mg had higher survival and growth than Mt in all areas except the high intertidal. Each species had similar growth rates when grown in single and mixed-species groups. Mg had higher survival and growth rates than Mt under both high and low salinity. These results indicate that the introduced Mg has superior growth and survival to the native Mt, and Mg has the potential to outcompete Mt under certain environmental conditions.