Extent of anadromy in bull trout and implications for conservation of a threatened species

The use of radiotelemetry revealed that adult bull trout Salvelinus confluentus moved between freshwater and the Pacific Ocean and between watersheds along coastal Washington. Forty-seven of 82 radio-tagged bull trout implanted in the Hoh River and Kalaloch Creek basins were anadromous, and 23 fish were relocated in five different estuaries up to 47 km south of their tagging locations. Anadromous bull trout typically entered the Hoh River from May to July, ascended as far as 78 km Upstream to spawning areas by September, and returned to the ocean to overwinter. This is the first study to verify that anadromy is a primary life history form in coastal bull trout. The presence of anadromy and the irregular periods of freshwater, estuarine, and marine residence observed ill this Study are consistent with observations reported for other Salvelinus species. These results also demonstrate that anadromous bull trout inhabit a diverse range of estuarine, freshwater, and marine habitats. Their affinity to estuaries and their observed temporal movements suggest that bull trout optimize winter refugia and forage opportunities and are Susceptible to incidental mortality in gill-net and recreational fisheries directed at other Pacific salmonids. An understanding of the extent of anadromy, sources of mortality, and diversity of habitats Occupied by bull trout is informative in the establishment of appropriate conservation and recovery strategies for this species.