Early Life History of Fishes in the San Francisco Estuary and Watershed

Juvenile Fishes of the Lower Feather River: Distribution, Emigration Patterns, and Associations with Environmental Variables

Alicia Seesholtz, Bradley J. Cavallo, Jason Kindopp, and Ryon Kurth

doi: https://doi.org/10.47886/9781888569599.ch10

Abstract.—In the Feather River below Lake Oroville, California, the relative importance of water temperature and flow regimes on fish populations was assessed by comparing two distinct river segments, the low flow channel (LFC) and high flow channel (HFC). Rotary screw traps and beach seining surveys were used to assess distribution, abundance, and emigration patterns of fishes between 1997 and 2001. Both sampling methods revealed similar patterns in species composition. Chinook salmon Oncorhynchus tshawytscha dominated seining (46%) and rotary screw trap (99%) catch by number. More than 80% of Chinook salmon captured were less than 50 mm, demonstrating that most Feather River Chinook salmon emigrate before smolting. In multiple linear regression models, Chinook salmon spawn timing (P < 0.001) and water temperature (P = 0.036) were statistically significant predictors of weekly Chinook salmon catch in the LFC, while Secchi depth was statistically significant (P = 0.007) for the HFC catch. Most steelhead Oncorhynchus mykiss were captured in the LFC, particularly in 2001, which accounted for 82% of all steelhead collected. The total relative abundance of alien fishes was low, 7.2% and 0.1% from beach seining and rotary screw trap sampling, respectively. Alien fishes were more abundant in the HFC. Native fish species were found throughout the study area. Canonical correspondence analysis suggested that river kilometer, water temperature, and year were highly significant (P = 0.001), while season (P = 0.01) and flow (P = 0.01) were significant to observed fish assemblages within LFC. Water temperature, river kilometer, year, and season were highly significant (P = 0.001) to observed fish assemblages within the HFC. Our results demonstrate that native fishes can be successful in a regulated river environment, despite an unnatural flow regime. These findings provide valuable information in assessing the impacts of dam operations and in implementing river restoration actions by flow and water temperature manipulation.