Assessing juvenile sockeye salmon (Oncorhynchus nerka) energy densities and their habitat quality in the Chignik watershed, Alaska

Abstract

The Chignik watershed, on the southern side of the Alaska Peninsula, supports a large salmon fishery vital to the local economy. Recent morphological changes to the watershed generated concern regarding the sockeye salmon (Oncorhynchus nerka) stock that rears in Black Lake, at the head of the system. Studies of the Chignik watershed to date have not incorporated energy density data to explain the life history strategies of Chignik sockeye salmon. Re-estimated condition factor parameters improved our understanding of the length-weight relationships to fish health that isometric models described in Chignik sockeye salmon. Subsequent comparisons of age, length, weight, location, and temperature data to energy density indicated that Black Lake fish, which were all age 0 fish, were significantly affected by temperature and had energy densities greater than did fish from other areas of the watershed. Sockeye salmon captured in Chignik Lake, Chignik River, and Chignik Lagoon were only energetically different from one another based on age. Observed seasonal trends suggested juvenile sockeye salmon emigrate from Black Lake before the onset of winter due to forage and temperature limitations. A constant downstream migration occurred in the watershed during the summer, which suggested smoltification and osmoregulation processes in Chignik Lagoon fish.