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Factors Affecting Survival Rates of a Recovering Lake Trout Population Estimated by Mark–Recapture in Lake Superior, 1969–1996
Author(s) -
Pollock Kenneth H.,
Yoshizaki Jun,
Fabrizio Mary C.,
Schram Stephen T.
Publication year - 2007
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/t05-317.1
Subject(s) - salvelinus , trout , mark and recapture , fishery , biology , hatchery , population , relative survival , fish <actinopterygii> , akaike information criterion , shoal , ecology , demography , statistics , mathematics , sociology , cancer registry , oceanography , geology
We used data from a long‐term Wisconsin Department of Natural Resources mark–recapture study to examine the dynamics of survival in a recovering population of lake trout Salvelinus namaycush in western Lake Superior from 1969 to 1996. Survival rates were estimated using the Cormack–Jolly–Seber method, and a series of models were constructed to examine the effect of year, size, sex, and origin (hatchery versus wild) on the survival rates of lake trout captured within the Gull Island Shoal refuge established in 1976. To select among the models, we used Akaike's information criterion corrected for small sample size and overdispersion. Our estimates of survival rates were adjusted using previously published tag loss rates for the three types of tags used since 1969. Survival estimates for wild fish varied widely among years; the lowest survival rates were observed in 1973 and 1974 and again in 1985 and 1986. Survival rates of wild fish were dependent on sex and size: Survival rates for male lake trout were 7% lower on average than those for female fish (means, 0.76 and 0.83), and large‐sized fish tended to have higher survival rates. Survival rates of hatchery‐reared fish could not be estimated for the entire time period owing to sample‐size issues; however, between 1983 and 1996 we found that hatchery fish survival rates were on average about 3% lower than those for wild fish. Survival estimates within the refuge were higher than estimates reported by others for fish outside the refuge and slightly higher than estimates from other Great Lakes studies.