Swimming Stamina and Survival following Direct Seawater Entry during Parr-smolt Transformation Of

Swimming atamina and survival in reletion to severe rtrees (swimmlng fatipue) were ameased in Pteah water and ssawater during varioua stages of the parr-amolt transformation for both 0-age and yearling coho salmon (Oncorhynchw kisutch). It waa determined that coho salmon normally experience transient reductions in ntarnina when ttanrfsrred directly to seawater. Coho salmon a h experience tranoient reductions in their ability to survive severe physical atreaa (swimming fatigue) at direct aeawater entry. Strese survival during the first week of rsawater residence was significantly correlated to the utatu~ of smoltification, with the maximum ability to survive rtreaa coinciding with the freshwater developmental peaks of both p lume thyroxine (T,) and gill Na+-K+ ATPaps.