Intermittent Streams as Rearing Habitat for Sacramento River Chinook Salmon: 1996 Update
Paul E. Maslin
William R. McKinney
and
Teri L. Moore
Abstract
The investigation of nonnatal rearing of juvenile chinook salmon (Oncorhynchus tshawytscha) in intermittent tributaries to the Sacramento River was continued another season. This year effort was concentrated in two streams, Mud Creek, near Chico, and Blue Tent Creek, near Red Bluff, with spot-checks of a few other streams. Mark and recapture techniques were employed to determine tributary residence time, permit more precise estimation of growth rate, and provide a rough estimate of density.
This year 4356 juvenile chinook were captured including 431 endangered winter chinook. Many of the juveniles captured were in the size range to be classified as spring chinook. However, faster growth in tributaries invalidates use of the daily length chart for distinguishing fall and spring juveniles. Growth in Mud Creek (1.14 mm/day) and Blue Tent Creek (0.94 mm/day) was calculated from size changes in marked and recaptured cohorts. (During the same time period, the daily growth chart assumes a growth rate in the Sacramento River of only 0.48 mm/day.)
Despite inaccuracy in classification, a much higher number of "spring" juveniles in Mud Creek (located down-river from spring chinook spawning tributaries) than in Blue Tent Creek (located upriver from spring chinook spawning tributaries) suggests that spring chinook juveniles also use intermittent tributaries for rearing. Definitive identification studies are needed.
Benthos collections showed presence of ample food in the tributaries. Stomach content analysis coupled with the consistent high condition of tributary-rearing chinook suggest efficient use of the available food.
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