Freshwater Survival of Stranded Steelhead Kelts in Coastal Central California Streams

Abstract

During 2008, spring drought conditions in the Santa Cruz Mountains of California resulted in hundreds of postspawn adult steelhead Oncorhynchus mykiss becoming stranded in streams and unable to return to sea. These individuals had no other option than to spend the entire summer and fall in freshwater habitats. As the fate of stranded kelts is poorly documented, we attempted to estimate the oversummer survival of steelhead kelts and to assess whether local habitat characteristics influenced survival rates. We found that nearly 40% of kelts observed during summer surveys were still alive in late October, just before the first significant rains of the season, and most individuals were observed to be in fair condition. Survival was higher for fish that resided in pools with substantial cover than for fish that occupied pools with only partial or no concealment. Overall, the unexpectedly high survival rates of stranded kelts suggest that the rescue and relocation of stranded steelhead to other habitats or to hatcheries may only be warranted when there are clear imminent threats to survival. Managers should consider the effects of strandings on population viability given that climate change may increase the frequency of strandings and decrease the survival of stranded individuals.

Received September 28, 2010; accepted April 28, 2011

ACKNOWLEDGMENTS

We would like to thank S. Beyer, H. Fish, and K. Pipal (National Marine Fisheries Service) for assisting with field surveys. D. Rundio and T. Williams (National Marine Fisheries Service) provided helpful comments on an earlier version of this manuscript. We are also grateful to the associate editor and an anonymous reviewer for providing constructive comments that greatly improved the manuscript. Reference to trade names does not imply endorsement by the U.S. Government.