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Last modified
7/14/2009 5:02:32 PM
Creation date
5/22/2009 5:33:47 PM
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UCREFRP
UCREFRP Catalog Number
8099
Author
American Fisheries Society.
Title
Proceedings of the 21st Annual Meeting, Colorado - Wyoming Chapter, American Fisheries Society.
USFW Year
1986.
USFW - Doc Type
March 5-6, 1986.
Copyright Material
NO
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<br />During 1981 and 1985, the largest number of fish were tagged in the Open Hills area, while in <br />1982, most of the fish were tagged in the Inflow area. In 1982 and 1985, ths smallest number of fish <br />were tagged in the Canyon. Netting in the Canyon is very difficult because of the steep sloping <br />canyon walls and almost non-existent littoral areas. <br /> <br />The first year exploitation rate for fall 1981 tagged lake trout was 4.3% (May 1, 1982 to April <br />30, 1983), while the first year exploitation rate for spring 1982 lake trout was 9.9% (May 1, 1982 to <br />April 30, 1983). The exploitation rates for lake trout during these two narrowly spaced time periods <br />should be closely linked. The total exploitation rate for the fall 1981 tagged fish (14.3%) and the <br />spring 1982 tagged fish (28.9%) clearly shows the fall fish have not returned at the same rate as the <br />spring tagged fish. The discrepancy in exploitation rates between fall and spring tagged fish is <br />explained by differential stress-induced mortality. The fall-tagged fish were in the process of or had <br />just completed spawning. Netting procedures had not been standardized and many netted fish were <br />caught in sets that were of 12 to 14 hours duration. These factors undoubtedly attributed to higher <br />mortality rates of fall 1981 tagged fish. For these reasons, all lake trout tagging for the 1985, as well <br />as the 1986 through 1988 exploitation studies, will be done in the spring. <br /> <br />A full, fIrSt year rate of exploitation for the spring 1985 tagged lake trout will not be available <br />until April 30, 1986. However, at 13.3%, the rate of exploitation for this group of fish to date <br />already exceeds the 1982 exploitation rate of 9.9% (as of March 4, 1986). <br /> <br />Figure 1 displays the length frequency of tagged lake trout for each tagging period. The lake <br />trout tagged during the fall of 1981 had the highest average length of the three tagging periods. These <br />fish averaged 28.5 inches in total length and ranged in length from 11.8 to 37.2 inches. The average <br />length of spring 1982 and 1985 lake trout were very similar. The 1982 tagged fish averaged 26.5 <br />inches and ranged from 15.3 to 39.0 inches. The 1985 tagged lake trout averaged 26.1 inches in <br />length and ranged from 14.0 to 39.5 inches. <br /> <br />Figure 2 depicts the length frequency of lake trout observed in fishermen's creels. The <br />average length of the returned lake trout when they were tagged (26.4 inches) compares favorably to <br />the average length of all lake trout tagged in 1985 (26.1 inches). <br /> <br />Almost 40% of all tagged fish returned were caught less than 5 miles from the site where they <br />were tagged. Over 50% of all lake trout were caught within 10 miles of the tagging site. One fish, <br />tagged in Big Bend of the Inflow area, was caught near the darn at Cart Creek. The fish had moved <br />approximately 45 miles down reservoir from the tagging site. A general northerly movement of lake <br />trout occurs in the fall as water temperatures and dissolved oxygen conditions become favorable in <br />the Inflowarea. In the spring, these conditions are reversed, and lake trout tend to move south. <br /> <br />It appears there is significant mixing of fish from the Inflow and Open Hills and some <br />movement between the Canyon and Open Hills, but very little mixing of lake trout from either the <br />Inflow or Open Hills to the Canyon. The need to equalize sampling throughout all reservoir areas <br />and zones so results of future exploitation studies reflect the exploitation of the entire population of <br />lake trout in Flaming Gorge is evident <br /> <br />In order to evaluate short term survival, studies were completed in 1982 and 1985. On May 5, <br />1982, eight lake trQut were held in the live cars to analyze the effects of netting, handling and tagging <br />procedures. The lake trout were captured at a depth of 30 feet in the Inflow area. Several of these <br />fish bled profusely from the gill area after their release from the net Most were badly tangled in the <br />net, requiring a considerable amount of handling. A few of the fish were so badly tangled they could <br />not expell air while being hauled to the surface and suffered from loss of equilibrium because of air <br /> <br />19 <br />
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