Non-natal habitat use by juvenile chinook salmon: Seasonal use and importance in the upper Yukon River drainage

INVESTIGATOR: Finn, James E.

PROJECT DESCRIPTION:
This multi-year investigation is designed to evaluate the use of freshwater non-natal stream and slack water habitats by rearing chinook salmon in the middle Yukon River drainage. The general model for the distribution of rearing chinook involves limited use of slack water habitats due to competition with species such as juvenile coho salmon and rainbow/steelhead trout. However, our observations and ongoing Canadian research in the Yukon River headwaters indicate that, in the absence of such inter-specific competition, juvenile chinook use stream, side-channel, and slack water habitats for both summer and winter rearing. Ongoing chum salmon research in the Chena River (Hodgins Slough) provides an excellent opportunity in terms of field facilities, detailed habitat maps, and logistical support to address questions concerning the freshwater ecology of chinook salmon and the importance of side-channel habitat to their productive capacity. In general we will be using minnow trap sampling, either mark-recapture or removal abundance estimates, and habitat mapping to determine: habitat use, growth, survival, seasonal timing, and site fidelity for juvenile chinook salmon in Chena River (Hodgins Slough) study site. A genetic component will be used to assess the geographic (within the Chena River drainage) importance of Hodgins Slough as non-natal habitat. Under this component, we will compare juveniles in Hodgins Slough with geographically proximate adult spawning aggregations to determine if the juvenile fish using the slough are progeny from localized aggregations. We will evaluate methods, population estimation techniques, and use preliminary results to develop and refine sampling designs in the first year. Under this study we propose to evaluate: a) Passive integrated transponder (PIT) tags in terms of retention and effects on growth and survival under field conditions. b) The use of non-destructive removal methods for population estimation. c) The seasonal movement patterns of juvenile chinook into and out of Hodgins Slough. d) The feasibility of estimating the over-wintering population of juvenile chinook in the slough using mark and recapture or non-destructive removal methods. e) The geographic (in terms of the Chena River drainage) importance of the Hodgins Slough for rearing chinook (genetic component).