Condition of juvenile chinook salmon in the upper Sacramento River, California

The physical condition of juvenile chinook salmon, Oncorhynchus tshawytscha , rearing in the upper Sacramento River during 1995 and 1996 was compared t o the condition of experimentally reared fish. The overall length-wet weigh t relation for field-caught juvenile salmon was allometric, resulting in a positive relation between condition factor (K) and fish size. Mean length, weight, and K increased, and mean percent body water decreased, over the st udy period. Though mean length and weight increased from upstream to downst ream sites, there were no distinct spatial trends in K or percent body wate r. Analysis of covariance showed weight at a given length in Sacramento Riv er chinook salmon increased progressively from February through June 1996 f or salmon 50-90 mm fork length. Field-caught chinook salmon were generally in better condition, as measured by weight and percent body water at all le ngths, than salmon from starved experimental treatment groups.