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Supplemental Stocking for Estimating Population Size and First‐Year Survival of Fingerling Rainbow Trout Stocked in a Utah Reservoir
Author(s) -
Hepworth Dale K.,
Duffield Daniel J.,
Modde Timothy
Publication year - 1991
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/1548-8675(1991)011<0011:ssfeps>2.3.co;2
Subject(s) - hatchery , rainbow trout , stocking , fishery , population , trout , biology , fish <actinopterygii> , mark and recapture , fish hatchery , population dynamics of fisheries , zoology , fish farming , aquaculture , demography , sociology
The traditional method of estimating population size with mark‐recapture techniques was compared to estimates made by using stocked hatchery fish as the sample of marked fish. The study was conducted on a 401‐hectare reservoir with a put‐grow‐and‐take sport fishery for rainbow trout Oncorhynchus mykiss . Populations were estimated in September 1987 and 1988 for rainbow trout (mean total lengths [TL] of 212–226 mm) that were stocked between March and June as fingerlings (89–102 mm TL). Population estimates for the mark‐recapture and hatchery‐fish methods, respectively, were 68,000 and 67,000 in 1987 and 51,000 and 63,000 in 1988. Survival estimates for stocked fingerlings ranged from 39 to 55% in 1987 and from 19 to 25% in 1988. The numbers of marked‐and‐released fish recaptured were proportionally similar to recaptures of hatchery fish used as the marked fish sample; there was no significant difference in recapture rates between methods. Confidence limits of the estimates were much narrower for the hatchery‐fish method because of larger sample size. Thus, use of hatchery fish as the marked fish sample removed the limitation of low sample size that commonly restricts the use of population estimation for management. Supplemental stocking of hatchery fish also made it possible to estimate the population size of older rainbow trout of larger size (380–394 mm mean TL). Assumptions used to make estimates were evaluated, which was necessary to validate population estimates based on use of hatchery fish.