Scott River Brood Year 2013 Juvenile Coho Salmon PIT Tagging Study

Extremely low flow conditions occurred in the Scott River watershed during the summer and fall of 2013 and 2014, due to the combined effects of drought and irrigation water withdraws. Low flows and disconnected
tributaries limited the extent of upstream migration of a relatively large adult coho return (n=~2,731) in 2013. Most spawning occurred in the mainstem Scott River rather than in the tributaries where it is more commonly
documented. This resulted in a situation where large numbers of juvenile coho were likely to be subject to high mortality rates in drying reaches of the Scott River. The California Department of Fish and Wildlife (CDFW), in
collaboration with other organizations, agencies and landowners undertook a fish relocation effort to remove juvenile salmonids from drying sections of the Scott River and place them in other locations in an attempt to
reduce the rate of mortality. Based on snorkel survey observations, over 118,250 juvenile coho were estimated to be present in the mainstem Scott River between Etna Creek and the Fay Lane Bridge in May 2014. An estimated 115,999 juvenile coho were relocated from the Scott River mainstem to tributary locations. A total of 1,872 of the relocated coho were implanted with passive integrated transponder (PIT) tags and CDFW operated six instream PIT tag detection stations in the watershed to evaluate the movements and survival of PIT tagged fish. A sample of 1,423 juvenile coho were also PIT tagged and released at the point of capture (981 were PIT tagged prior to September 1, 2014 and 442 were PIT tagged on September 1, 2014 or later) so that we could compare movements and survival between tagged fish that were relocated and those that were not. In addition, a total of 4,447 juvenile coho were taken to Iron Gate Hatchery (IGH) to rear in circulating round tanks. Of those fish, 390 were PIT tagged. These fish were returned to the mainstem Scott River and French Creek in October 2014.