|Document Type:||Contract Report|
|Title:||Alternative barging strategies to improve survival of salmonids transported from Lower Granite Dam: final report from the 2006–2008 spring/summer Chinook salmon and steelhead juvenile migrations|
|Author/Editor:||Tiffani M. Marsh, William D. Muir, Benjamin P. Sandford, Steven G. Smith, Diane G. Elliott|
|Publisher:||National Marine Fisheries Service|
|Contracting Agency:||U.S. Army Corps of Engineers. Walla Walla, Washington|
|Contract Number:||W68SBV60307671 and W68SBV60418618|
In 2011, the final year class of adult salmon Oncorhynchus spp. returned from smolt groups released for a multi year study to evaluate an alternate release site for transported fish. Smolts were collected and tagged at Lower Granite Dam, transported, and released at the alternate site near Astoria, Oregon (river kilometer 10) or at the traditional release site near Skamania Landing (rkm 225) just downstream of Bonneville Dam.
Study fish were juvenile steelhead O. mykiss and yearling spring/summer Chinook salmon O. tshawytscha, and our evaluation was based on comparisons of smolt–to–adult return rates (SARs) between replicate paired groups. Our hypothesis was that moving the traditional barge–release site 215 km downstream could increase adult returns by decreasing smolt mortality due to predation by piscivorous fish and birds. Paired groups were released weekly over 6 weeks during the migration seasons of 2006, 2007, and 2008. The last adult steelhead from these releases returned in May 2011 (2–ocean), and the last adult Chinook salmon in August 2011 (3–ocean).
We found no evidence of a consistent difference in SARs between fish groups released at the two barge–release locations. Data were not sufficient to evaluate the effects of fish pathogens on avian predation. There was clear evidence that fish of both species released at Astoria were less vulnerable to avian predators than those released at the customary site at Skamania Landing. Unfortunately, this survival benefit did not translate to higher SARs, as it was offset by higher rates of straying by fish released from Astoria. This was likely a result of greater impairment to homing ability for fish released at Astoria.
|Theme:||Recovery and rebuilding of marine and coastal species|
Develop methods to use physiological, biological and behavioral information to predict population-level processes.