Stock assessment of Arctic grayling in Piledriver Slough during 1994

Description

A mark-recapture experiment was conducted on Arctic grayling Thymallus arcticus in Piledriver Slough, near Fairbanks, Alaska during 1994. A weir was used to characterize immigration and capture fish for mark-recapture sampling. The weir was fished over a 51 day period beginning in mid-April. A total of 933 Arctic grayling were passed upstream, and 447 fish passed downstream following the mark-recapture experiment. The upstream weir catches were used as the marking sample while catches from a single downstream pass by an electrofishing crew were used as the recapture sample. An estimated 11,747 (SE = 1,297) Arctic grayling > 150 millimeters fork length were present during the early May spawning period. Use of the weir indicated that closure existed for mark-recapture sampling, as very few fish relative to the population size immigrated after the marking event, and few fish had emigrated by the 2 June completion of the weir project. The 1994 stock was characterized by a higher proportion of legal-sized Arctic grayling ( 270 millimeter fork length) than that estimated in 1993, and the age composition was predominated by age 4 fish. The estimated survival was 64%, which indicated more of the stock survived natural and fishery losses in 1993 than in past Piledriver Slough assessments. Restrictions to a no-harvest regulation in 1993 led to lower estimates of exploitation, but estimates of potential exploitation resulting from high catch rates and hooking injury, indicate exploitation rates may still be high.

Subjects

Genres

• Statistics

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