Author : Frederick A. Goetz
Publisher :
ISBN 13 :
Total Pages : 187 pages
Book Rating : 4.:/5 (962 download)
Book Synopsis Migration and Residence Patterns of Salmonids in Puget Sound, Washington by : Frederick A. Goetz
Download or read book Migration and Residence Patterns of Salmonids in Puget Sound, Washington written by Frederick A. Goetz and published by . This book was released on 2016 with total page 187 pages. Available in PDF, EPUB and Kindle. Book excerpt: The overall period of marine residence was similar among fish from different river basins and life stages; larger bull trout entered marine waters in late winter-early spring, juveniles in late spring, and most fish migrated back into rivers by late spring-early summer as temperatures were increasing. However, the timing of return migration was similar among rivers despite differences in their thermal regimes. Some fish entered and exited the rivers in the fall but few overwintered in marine areas. Most fish occupied estuary and nearshore areas near natal rivers but some moved over 100 km from the river mouth. These timing patterns and use of marine habitats contrast strongly with those of other salmonids in Puget Sound, revealing the diversity in migratory behavior under the broad category of anadromy, and emphasizing the importance of estuarine and nearshore habitats for the conservation of bull trout, listed as Threatened under the U. S. Endangered Species Act. Behavioral thermoregulation by adult Chinook salmon (Oncorhynchus tshawytscha) and comparison to sockeye salmon (O. nerka) in estuary and freshwater habitats prior to spawning The movements and thermal experience of Pacific salmon during their homeward migration through marine waters and into freshwater systems pose challenges for their physiology, especially in river basins altered by human structures and activities, and under regimes of increasingly high temperatures. This study determined the thermal regimes experienced by maturing Chinook salmon, Oncorhynchus tshawytscha, entering the Lake Washington basin via a navigational locks and canal, and migrating through the lake to spawning grounds or hatcheries. We then compared these patterns, determined from a combination of acoustic tracking and temperature loggers attached to the fish, with comparable data on sockeye salmon collected in an independent study in overlapping years. Chinook salmon exhibited complex patterns, occupying cool water refuges in stratified marine and freshwater areas: 1) in Puget Sound (28-30 ppt, 12-15 oC), 2) in deeper water in the salt wedge (upper estuary) above the locks (12-15 ppt, 18-21 oC), and 3) intermittently in deeper fresh water in Lake Washington (9-21 oC). Most Chinook salmon (> 75%) left the estuary after tagging and spent a short period (mean 4.6 d) in Puget Sound). Upon return to the upper estuary Chinook salmon either held in a small, cool area in the salt wedge (mean 11.1 d) or went back to Puget Sound twice to hold in tidally influenced saltwater. Sockeye salmon exhibited a fairly simple migration pattern, holding for a short period in warm water (median 18.4 oC) in the upper estuary and canal (mean 3.6 d), then migrating to the lake and residing in cold-water areas (mean 10.3 oC) at depths of 40 m (mean 88.3 d). Sockeye and Chinook salmon travelled through a 10.8 km canal to Lake Washington in relatively short periods, 2 d and 0.5 d (mean) respectively, but Chinook salmon experienced higher temperatures (20-22.5 oC) because they migrated later in summer. In Lake Washington Chinook salmon exhibited vertical migrations above and below the thermocline and used the lake as a thermal refuge to a lesser extent than did sockeye salmon, which remained below the thermocline almost exclusively until they ascended rivers to spawn. Individual fish utilized different migration paths and so had distinct thermal experiences but survived to reach breeding sites. The ability to exploit multiple refuges in this highly modified migratory corridor may be essential for the persistence of these species and especially the Chinook salmon. In the face of climate change, understanding how fish use available thermal refuges may help identify management alternatives to retain or increase these areas in the future.
