Marking, enumeration, and size estimation for coho and chinook salmon smolt releases into upper Cook Inlet and Resurrection Bay, Alaska in 1997

Description

Over half of Alaskans live in Southcentral Alaska, which receives the vast majority of the states sport fishing effort. The population of Southcentral and sport fishing effort are increasing. To meet the growing demand on the sport fishery resource, hatchery-reared chinook salmon Oncorhynchus tshawytscha and coho salmon O. kisutch smolt have been stocked in numerous locations throughout Southcentral Alaska to improve or create terminal sport fisheries. Over 730,000 coho and chinook salmon smolt released at 10 locations in Cook Inlet and Resurrection Bay were marked with an adipose finclip and a coded wire tag in 1997. Tag retention for individual raceways ranged from 93.6% to 99.6%. Our production goal for coho salmon was to make 80% of the smolt within the size range of 15.1 g to 25.0 g. Coho salmon produced at Ft. Richardson Hatchery and released into Campbell Creek and Ship Creek were extremely close to meeting the goal. Our production goal for chinook salmon smolt was to make 80% of the smolt within the range of 5.1 g to 15.0 g. Ninilchik River and Deception Creek chinook salmon smolt produced at Ft. Richardson Hatchery, as well as the Lowell Creek and Homer Spit late-run chinook salmon release groups at Elmendorf met this goal. None of the remaining chinook salmon release groups at Elmendorf Hatchery, nor the Bird Creek coho salmon release group at Fort Richardson Hatchery achieved the production goal. Three smolt enumeration estimation techniques were compared. At Fort Richardson Hatchery, the hatchery inventory estimate appeared to be the most accurate of the three estimation techniques when compared to physical counts, and in a comparison of mark-recapture estimates to physical counts it appears that the mark-recapture technique tends to underestimate the population within a rearing unit. Therefore, at Fort Richardson Hatchery we used the physical count where possible, and the hatchery inventory estimate elsewhere for estimating numbers of smolt released. At Elmendorf Hatchery, the mark-recapture estimate is the highest of the three enumeration estimation techniques for half of the rearing units. The water volume estimate was higher than the hatchery inventory estimate in most instances at Elmendorf Hatchery. In most instances, the differences between hatchery inventory estimates and mark-recapture estimates at Elmendorf Hatchery depended upon the method used to obtain the hatchery inventory estimate. The mark-recapture method was used for obtaining numbers of smolt released from Elmendorf Hatchery.

Subjects

Series Statement

• Fishery data series -- no. 99-1.

Links

• URL