Stock status and rehabilitation of Chena River arctic grayling during 1991 and 1992
By: by Robert A. Clark.
Contributors: Alaska. Division of Sport Fish.
Series: Fishery data series -- no. 93-5.
Publisher: Alaska Dept. of Fish and Game, Division of Sport Fish
Published: 1993
Place of publication: Anchorage, Alaska
Language: eng
Number of pages: 66
Subjects: Arctic grayling -- Alaska -- Chena River.; Fish populations -- Alaska -- Chena River.
Other titles: Federal aid in sport fish restoration (Alaska)
Description: Stock status of Arctic grayling Thymallus arcticus in the lower 152 kilometers of the Chena River was described by population abundance, age composition, size composition, recruitment, and survival rate estimates during 1991 and 1992. In July of 1991, estimated abundance of Arctic grayling in the Chena River was 26,756 fish (SE was 3,286 fish)  150 millimeter fork length. Age 4 Arctic grayling were strongly represented in the Chena River, representing 51.9 percent of fish  150 millimeter fork length. Stock size Arctic grayling (< 270 millimeter fork length) represented 73.3 percent of fish  150 millimeter fork length. Annual recruitment between 1990 and 1991 was 2,882 Arctic grayling and annual survival during this period was 74.8 percent. In July of 1992, estimated abundance of Arctic grayling in the Chena River was 29,349 fish (SE was 2,341 fish)  150 millimeter fork length. Age 5 Arctic grayling were strongly represented in the Chena River, representing 38.0 percent of fish  150 millimeter fork length. Stock size Arctic grayling (< 270 millimeter fork length) represented 78.0 percent of fish  150 millimeter fork length. Annual recruitment between 1991 and 1992 was 5,773 Arctic grayling and annual survival during this period was 78.8 percent. Precision of mark-recapture experiments was improved from prior years by performing single-sample experiments in the entire Lower Chena section (river kilometer 72 to 0). Abundance of Arctic grayling appears to have stabilized, although there was no recreational harvest during the period of stock assessments. Total mortality rate (one minus the survival rate) between 1991 and 1992 could be considered a estimate of natural mortality plus any illegal harvest and incidental hooking mortality. An egg take was performed during 1992, with approximately 206,000 eggs taken. Of these eggs, approximately 109,500 survived to the 0.5-gram fry stage (38 millimeter fork length). Average fecundity of 49 female Arctic grayling was 3,090 eggs (SD was 1,917 eggs). Approximately 34,000 fry were transferred to a pen rearing facility. A 42 day rearing period resulted in 23,199 2.7-gram fingerlings (65 millimeter fork length) released into the Chena River on 11 September 1992. Persistent cold water temperature delayed maturation of adults during the egg take, possibly causing low egg-to-fry survival. A rearing period of 42 days resulted in less than anticipated growth; earlier maturation of adults in 1993 should result in a longer rearing period for fry. With a longer (60 day) rearing period in 1993, the desired size at release in 1993 should be attained (10 gram or 100 millimeter fork length).
Notes: "Partially financed by the Federal Aid in Sport Fish Restoration Act ... under project F-10-7 and F-10-8, job no. R-3-2(a)."

"March 1993."

Includes bibliographical references (p. 42-47).

Also issued online.