Cooperation of shellfish growers and biologists in detecting andmonitoring invasive species: The European green crab invasion inOregon

摘要

The recent invasion of Pacific Northwest estuaries by the European green crab, Carcinus maenas, initially caused much alarm. Following the strong El Nino of 1997-98, young green crabs appeared in estuaries along the coasts of Oregon, Washington, and as far north as Nootka Sound on the west coast of Vancouver Island, British Columbia. Heath Hampel, a shellfish grower, in Coos Bay, Oregon played a critical role in alerting biologists in this invasion, thus allowing us to document and interpret the invasion process. Unusually strong northward-moving coastal currents of up to 50 km/day during strong El Nino events correlated with good recruitment and northward range expansions of green crabs. It thus appears that these currents transported larvae from more established populations in California to Northwest estuaries. Since the last El Nino, coastal transport events have been much weaker and green crab recruitment much lower. Shellfish growers and sports crab harvesters in Oregon and Washington also help biologists determine the age structure of the green crab population by taking their captured green crabs to extension offices. From carapace width and condition biologists can estimate age. For example, in the summer of 2003, we saw large individuals from the strong 1997-1998 year class decrease in numbers and smaller, younger crabs taking their place. While green crab abundance in the Northwest is still low, it is imperative to continue monitoring efforts to elucidate the process of range expansion of this non-indigenous marine species and to serve as an early warning system for the next strong recruitment event. However, as the novelty of a marine invader wears off and densities remain low, funding sources for studying the invasion dry up. As this happens, the role of shellfish growers and crab harvesters in reporting non-indigenous species sightings to biologists becomes increasingly important.