Author :
Publisher :
ISBN 13 :
Total Pages : 65 pages
Book Rating : 4.:/5 (727 download)
Book Synopsis Lake Roosevelt Fisheries Monitoring Program ; Artificial Imprinting of Lake Roosevelt Kokanee Salmon (Oncorhynchus Nerka) with Synthetic Chemicals by :
Download or read book Lake Roosevelt Fisheries Monitoring Program ; Artificial Imprinting of Lake Roosevelt Kokanee Salmon (Oncorhynchus Nerka) with Synthetic Chemicals written by and published by . This book was released on 1993 with total page 65 pages. Available in PDF, EPUB and Kindle. Book excerpt: In 1991, we initiated studies to determine the critical period for thyroxine-induced olfactory imprinting in kokanee salmon. In our preliminary investigation we found that thyroxine [T4] levels of Lake Whatcom stock, 1990 year class, kokanee were relatively high in eggs and alevins as compared to post-swimup fry, and peaked at hatch and swimup. Here we report on follow-up studies conducted in 1992 designed to determine if our initial results could be replicated. Additionally, in 1992, we initiated experiments to determine if kokanee could be imprinted to synthetic chemicals--morpholine and phenethyl alcohol--at different life stages. In 1991, whole body thyroxine content [T4] was measured in 460 Lake Whatcom stock kokanee and 480 Lake Pend Orielle (Cabinet Gorge) stock kokanee to indicate the critical period for imprinting. Lots of 20 kokanee eggs, alevins and fry from both stocks, reared at the Spokane Tribal hatchery, were collected at weekly intervals from November 1991 to August 1992 and assayed for T4 content by radioimmunoassay. T4 levels were monitored in Lake Whatcom stock, 1991 year class fish, from eyed egg (33 days post-fertilization) to fry (248 days post-fertilization) stages. T4 concentration (± SEM) in eggs was 6.7 ± 1.3 rig/g body weight. T4 peaked on the day of hatch at 13.1 ± 2.5 ng/g body weight, then declined to 10.3 ± 1.1 ng/g body weight in recently post-hatch alevins. T4 peaked again at 22.1 ± 5.2 ng/g body weight during swimup, then steadily decreased to about 1.0 ng/g body weight in 176-248 day old fry. T4 levels were monitored in Lake Pend Orielle stock, 1991 year class, fish from the day of fertilization (day 0) to 225 days post-fertilization. T4 content of eggs was 9.5 ± 1.7 ng/g body weight and peaked on the day of hatch (day 53 post-fertilization) at 24.2 ± 4.5 ng/g body weight. After declining to 13.0 ± 2.9 ng/g body weight on day 81 post-fertilization, T4 peaked a second time during swimup (88-95 days post-fertilization) at 24.3 ± 3.8 ng/g body weight. After swimup, T4 concentration steadily declined to about 0.6 ng/g body weight in 225 day old post-fertilization fry. Thus, results of our 1992 investigations were consistent with our preliminary 1991 study. In all cases: (1) T4 concentration was relatively high in eggs and alevins as compared to older fry; and (2) T4 peaks occurred at hatch and swimup. Blood serum T4 concentration was measured in 9 month to 21 month-old Lake Whatcom stock, 1990 year class, kokanee from July 1991 to August 1992. T4 concentrations were low in summer, peaked slightly in October, were low in early winter, then peaked several times between January and May 1992. Thus, the 1990 year class Lake Whatcom kokanee evidenced high T4 activity from egg to swimup stages in their first year and in the winter and spring of their second year of life. The fish appeared to undergo smolt transformation between 16-18 months old. In 1992, Lake Whatcom (1991 cohort) kokanee were exposed to synthetic chemicals--1,072,000 to morpholine and 1,117,000 to phenethyl alcohol--at different life history stages: (1) eye to hatch; (2) hatch; (3) hatch to swimup; (4) swimup; and (5) post-swimup fry (in February, March, April and May-June). Additionally, Lake Whatcom (1990 cohort) kokanee were exposed to synthetic chemicals--36,000 to morpholine and 51,600 to phenethyl alcohol--at age 16-18 months. Most of these fish were marked and released in Lake Roosevelt in July and August 1992 as part of a field test. A portion of the fish from each group was retained at the Spokane Tribal hatchery until August-October 1993, when behavioral tests will be conducted to determine if the fish imprinted to their exposure odor.
