Adult salmonids returning from the ocean, referred to as "pre-spawners," often remain in the estuary while waiting for favorable flows for upstream migration. Predation on anadromous salmonid pre-spawners by seals is probably significant. At present, the estuary provides pre-spawners with little cover from predation. In low water years, 25 to 30% of the returning steelhead show bite marks from seals (Waldvogel personal communication 1996). Because steelhead swim faster than chinook and coho, they are more likely to escape from an encounter with a marine mammal predator, which accounts for the greater number of bite marks on steelhead. The implication is that predation is higher on salmon due to their slower swimming speed.

This page is hosted by Get your own Free Home Page