Growth of Wild Subyearling Fall Chinook Salmon in the Snake River

Abstract

Abstract Growth is an important determinant of life history development for juvenile anadromous salmonids. We collected juvenile fall chinook salmon Oncorhynchus tshawytscha in two reaches of the Snake River to describe growth in fork length (mm/d) and to test for a relation between growth and water temperature. Growth rate during shoreline rearing was significantly higher (P = 0.003) for parr in the warmer of these two reaches (grand means = 1.2 ± 0.04 and 1.0 ± 0.04 mm/d). Because smolts from the two reaches share a common, relatively warm downstream migration route, growth rates were similar between smolts from the two reaches (P = 0.18; grand means = 1.3 ± 0.04 and 1.4 ± 0.04 mm/d). By pooling data across reaches and life stages, we found that growth rate generally increased as water temperature increased (N = 17, r 2 = 0.62, P = 0.0002). The growth rates we observed were probably lower than for fall chinook salmon in a historical rearing area now inaccessible because of dams, but they were still rapi...