Author : Mary Beth Tilson
Publisher :
ISBN 13 :
Total Pages : 300 pages
Book Rating : 4.:/5 (31 download)
Book Synopsis Smolt Transformation in Kokanee Salmon, Oncorhynchus Nerka Kennerlyi Suckley by : Mary Beth Tilson
Download or read book Smolt Transformation in Kokanee Salmon, Oncorhynchus Nerka Kennerlyi Suckley written by Mary Beth Tilson and published by . This book was released on 1994 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt: "In 1991, two kokanee salmon hatcheries were built on Lake Roosevelt to mitigate for the loss of anadromous salmon due to construction of Grand Coulee Dam. Fish are released into Lake Roosevelt as 7-8 month old fry. To monitor hatchery effectiveness, kokanee salmon were tested for a variety of physiological, behavioral and morphological attributes to determine if they went through smelt transformation similar to other anadromous salmonid species. This would help in determining if fish were emmigrating out of Lake Roosevelt and over Grand Coulee Dam at some point after stocking. Yearling fish,12-19 months old, retained at the Spokane Tribal Hatchery were tested at monthly intervals for plasma thyroxine, gill Na-K+ ATPase activity, condition factor, silvering, salinity tolerance, salinity preference and downstream migratory behavior. Results indicated a significant peak in plasma thyroxine in February and a smaller peak in April. Basal levels of thyroxine were 11.0 ng/ml compared to 15.2 ng/ml at peak. Gill ATPase increased from 5.1 [micro]mol P[subscript]i mg Protein−1 h−1 in January to 13.7 [micro]moI P[subscript]i mg Protein−1 h−1 in April, and condition factor decreased from 1.3 to 0.82 at this time. Silvering started to increase in February and continued through the spring. Blood plasma osmolarity of fish held in 0, 1 0, and 20 ppt stayed around isosmotic levels (330 mOsm/l), but the osmolarity of fish held in 30 ppt were significantly higher than fish held in freshwater, and osmolarity remained elevated from January through April, ( -569 mOsm/l) then decreased in May to near isosmotic levels (344 mOsm/l). In salinity tolerance tests, 100% of the fish survived in 0, 10, and 20 ppt salt water during all months tested (January- July). In 30 ppt salt water, 0% of the fish survived from January through April compared to 90-100% survival from May through July. Kokanee exhibited no preference to dilute salt water during the study period. Fish showed a slight preference to concentrated sea water in February (53%), but during March, April and May, fish exhibited an avoidance to salt water (43, 49, and 41% preference). In June, fish showed a strong avoidance to salt water (23% preference). Fish showed an increase in downsteam migratory behavior in March (66%) and again in May (65%). It appeared that kokanee underwent at least partial smelt transformation compared to other species of anadromous salmonids. These kokanee experienced thyroxine peaks, increased silvering, increased downstream migratory behavior and an increase in salt water adaptation at certain times of the year. If fish released from the hatchery as 7-8 month old fry experience similar transitions in Lake Roosevelt when they are 12-19 months old, these conditions may contribute to emmigration and entrainment through Grand Coulee Dam, and loss of the fish from Lake Roosevelt"--Document.
