Stock status of arctic grayling in the Chena River and Badger Slough during 1996

Description

Stock status of Arctic grayling Thymallus arcticus in the lower 152 km of the Chena River was described by population abundance, age composition, size composition, recruitment, and survival rate estimates during 1996. In July of 1996, estimated abundance of Arctic grayling in the Chena River was 42,850 fish (SE = 4,163) 150 mm FL. Age-3 Arctic grayling were strongly represented in the Chena River, representing 38 % of fish 150 mm FL. Stock-size Arctic grayling (150-269 mm FL) represented 66 % of fish 150 mm FL. Annual recruitment between 1995 and 1996 was 15,605 Arctic grayling (SE = 1,851) and annual survival during this period was 78.2 % (SE = 6.5). Estimated abundance of 1992 brood year (age-4) hatchery-reared Arctic grayling, released in 1993, was 815 fish (SE = 125). Survival of age-4 hatchery-reared Arctic grayling from July of 1995 to July of 1996 was 40.4 % (SE = 1.7). Estimated abundance of 1993 brood year (age-3) hatchery-reared Arctic grayling, released in 1994, was 573 fish (SE = 102). Survival of age-3 hatchery-reared Arctic grayling from July of 1995 to July of 1996 was 24.6% (SE = 1.4). From 1992 through 1994, a total of 126,371 age-1 and 23,199 age-0 Arctic grayling have been released into the Chena River. Estimated abundance of all releases of Arctic grayling in 1996 was 1,388 fish (SE = 161). Low initial post-release survival (~60% during the first month) and low overwinter survival (~8% per year) were the primary causes of failure of the releases. Stock status of Arctic grayling within 5.7 km of Badger Slough during May 1996 was described by abundance, age composition, and size composition. Additionally, the relative contribution was estimated for fish present in Badger Slough in May that were present in the Chena River in July. In May 1996, the estimated abundance of Arctic grayling in Badger Slough was 9,496 (SE = 1,801) > 220mm FL. Age-5 (28%) and age-6 (23%) fish predominated the age composition in Badger Slough during the spring spawning period. Arctic grayling between 250 and 289 mm FL comprised an estimated 48% of fish present. Relative contribution rate estimates indicated that 6% of Arctic grayling > 220 mm FL and 4% of fish > 270 mm FL present in July along the 152 km assessed portion of the Chena River were also part of the assessed stock in Badger Slough during May.

Subjects

Links

• URL