Floodplain rearing of juvenile chinook salmon: evidence of enhanced growth and survival

Juvenile Chinook salmon (Oncorhynchus tshawytscha) growth in off-channel and main-channel habitats on the Sacramento River, CA using otolith increment widths

“…Higher metabolic rates require adequate food to maintain higher growth rates. Our observations of higher prey densities in the warmer off-channel habitats are congruent with previous research on innundated floodplains (Gladden and Smock 1990;Sommer et al 2001) and shallow habitat interfaces (Welcomme 1979). We expected to see greater stomach fullness in habitats with greater prey densities due to higher feeding rates.…”

“…This result is interesting in the light of previous work on the benefits of alternative habitat for juvenile salmonids. Our results based on otolith microstructure support the findings of previous studies using alternative methods to evaluate growth improvements such as changes in abundance (Simenstad and Cordell 2000), change-in-length of fish (Swales et al 1986;Murray and Rosenau 1989) and mark/recapture techniques (Sommer et al 2001;Wigington et al 2006).…”

“…While regional differences exist between river systems, first year survival rates are likely important in the population dynamics of every salmonid stock (Holtby et al 1990;Sommer et al 2001). More information on juvenile salmonid performance in different habitats is needed to identify factors limiting their abundance during the freshwater phase (Swales et al 1986).…”

“…It has been suggested that the refuge that off-channel habitats provide from both high flows and high sediment loads may improve growth rates (Crouse et al 1981) and decrease mortality (Erman et al 1988). In addition, at the onset of floodplain and seasonal tributary inundation, the increase in overall available habitat is likely to both reduce competition and lower predation risk (Sommer et al 2001). Greater prey densities in offchannel habitat relative to the main-channel may also improve feeding rates and result in faster growth (Swales and Levings 1989).…”

Science Advancements Key to Increasing Management Value of Life Stage Monitoring Networks for Endangered Sacramento River Winter-Run Chinook Salmon in California

“…A desired response from restoring juvenile rearing habitats is increased fish growth and energy reserves, which correspond to increased survival in the ocean (Duffy and Beauchamp 2011;Woodson et al 2013). Evidence from within the Central Valley demonstrates that salmon reared on floodplains experience accelerated growth relative to individuals reared in more channelized habitats (Sommer et al 2001). Throughout the Delta, restoring shallow water habitats is expected to be important for fry migrants, depending on the response of the warm water predator community.…”