Author : Matthew L. Keefer
Publisher :
ISBN 13 :
Total Pages : 16 pages
Book Rating : 4.:/5 (124 download)
Book Synopsis Behavior and Survival of Radio-tagged Sockeye Salmon During Adult Migration in the Snake and Salmon Rivers by : Matthew L. Keefer
Download or read book Behavior and Survival of Radio-tagged Sockeye Salmon During Adult Migration in the Snake and Salmon Rivers written by Matthew L. Keefer and published by . This book was released on 2008 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Conservation efforts for critically endangered Snake River sockeye salmon (Oncorhynchus nerka) have been partially hindered by high en route mortality of adult fish during their ~1,450 kilometer freshwater spawning migration. Through the 1990s, Snake River sockeye were poised on the brink of extinction, with annual returns averaging fewer than five fish. A moderate recovery began in 1999, when the first adult progeny from a captive broodstock program returned from the ocean. The largest run in several decades returned in 2000, with 299 fish counted at Lower Granite Dam on the Snake River. Taking advantage of this rare opportunity, we collected and radio-tagged 31 adults at the dam and then monitored their migration behavior and survival over ~750 kilometers. Tagged fish migrated rapidly through the Lower Granite reservoir and successively more slowly through each upstream reach. Successful and unsuccessful fish migrated at similar rates through the lower study reaches, after which unsuccessful fish migrated significantly more slowly than successful fish. Survival dramatically declined late in the run after mean water temperatures exceeded 21 °C and daily maximums reached 23-24 °C. Several fish displayed thermoregulatory behavior during the warmest period, using cooler water from tributaries including the Clearwater and Grande Ronde rivers. Fish with injuries at the time of tagging (e.g., head injuries, lesions, gill net marks) were less likely to survive than fish without notable injuries. Notably, fish with injuries were concentrated in the later portion of the run, suggesting possible condition-dependent delay during migration in the lower Columbia and Snake rivers. Overall, results strongly suggest indirect sublethal temperature effects, possibly mediated by poor initial fish condition. Migration in water temperatures near tolerance thresholds may exacerbate mortality risks, and these risks are most likely for fish with later migration timing. In fact, sockeye salmon counts at Ice Harbor indicate that there may have been recent selection against later-timed adult sockeye salmon. High en route mortality of Snake River sockeye will likely persist or increase given projections for continued warming of their migration corridor."--Abstract (page iv).