Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8994
Title: Variability in the performance of juvenile Chinook salmon is explained primarily by when and where they resided in estuarine habitats
Author: P. M. Chittaro, Lyndal L. Johnson, David J. Teel, Paul Moran, S. Y. Sol, K. H. Macneale, Richard W. Zabel
Publication Year: In press
Journal: Ecology of Freshwater Fish
Abstract:

Estuarine habitats provide rearing opportunities for the juvenile life stage of anadromous fishes. Because survival is positively correlated with juvenile performance, these estuarine habitats play an important role in population abundance and productivity. To provide information for the recovery of several depressed stocks of Chinook salmon in the Columbia River Basin, we sought to identify the factors that explain variability in performance. Using otolith-derived estimates of juvenile somatic growth rate as an index of recent performance we observed a negative non-linear relationship between growth rate and day of year, and a decreasing and increasing trend of growth rate over the eight years of this study and distance from the river mouth, respectively. Using a generalized linear modeling approach, we found that variability in juvenile somatic growth rate was best explained by where and when individuals were collected, their body size, contaminant loads, stock of origin, and whether a fish was hatchery produced or unmarked.  Lastly, we argue that a considerable improvement to the growth rate of juveniles in estuarine habitats is physiologically possible. The results of this 8-year study provide a baseline of the performance of juvenile Chinook salmon to evaluate habitat restoration programs and to compare against future anthropogenic conditions.

Description:

We used otolith-derived estimates of somatic growth rate as an index of recent performance and together with a generalized linear modeling (GLM) approach investigated how variability in juvenile performance was explained by several abiotic and biotic factors. Our GLM approach indicated that variability in relative somatic growth rate (mm/mm/day) was best explained by when (i.e., Julian day and year) individuals were collected and to a lessor degree by where they were collected (i.e., river kilometer), fish and invertebrate density, stock of origin, and whether a fish was hatchery produced or unmarked.  Using this information we argue there is potential for improving juvenile performance within estuarine and tidal freshwater habitats.

Theme: Habitats to Support Sustainable Fisheries and Recovered Populations
Foci: Characterize relationships between habitat and ecosystem processes, climate variation, and the viability of organisms.