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Age, Growth, Survival, and Maturity of Lake Trout Morphotypes in Lake Mistassini, Quebec
Author(s) -
Hansen Michael J.,
Nate Nancy A.,
Krueger Charles C.,
Zimmerman Mara S.,
Kruckman Hanna G.,
Taylor William W.
Publication year - 2012
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 - 10.1080/00028487.2012.711263
Subject(s) - trout , biology , zoology , salvelinus , fishery , fish <actinopterygii> , range (aeronautics) , ecology , materials science , composite material
Life history characteristics (age, growth, survival, and maturity) were compared between the deepwater “humper” and shallow‐water “lean” forms of lake trout Salvelinus namaycush in Lake Mistassini, Quebec, to determine whether the two morphotypes may represent resource polymorphism. Lake trout were sampled using graded‐mesh (range = 51–114 mm stretch) gill nets set in deep and shallow waters. Humpers were typically caught in deep waters (>50 m) and averaged 474 mm TL (range = 389–616 mm) and 852 g in weight (range = 470–1,710 g), whereas leans were typically caught in shallow waters (<50 m) and averaged 525 mm TL (range = 301–865 mm) and 1,210 g in weight (range = 200–6,500 g). Humpers and leans did not differ in weight–length relationships and grew slimmer with length over a common TL range (389–616 mm). Average age of humpers was 27 years (range = 13–49 years); average age of leans was 21 years (range = 6–42 years). The two forms did not differ in total annual mortality ( A ) of fish older than 17 years, the first age beyond which numbers declined with age for both morphs ( A = 5.1%; 95% confidence interval = 2.4–7.8%). Humpers grew slower (annual growth rate ω = 53 mm/year) than leans ( ω = 68 mm/year) and to a shorter mean asymptotic length ( L ∞ = 514 mm) than leans ( L ∞ = 605 mm). Mature humpers (mean TL = 475 mm, SE = 9.0; N = 58) were shorter on average than mature leans (mean TL = 539 mm, SE = 8.5; N = 65); mature humpers (mean age = 27 years, SE = 1.0; N = 56) were also older on average than mature leans (mean age = 23 years, SE = 0.98; N = 61). We conclude that lean and humper forms of lake trout in Lake Mistassini differed in age, growth, and maturity; this is consistent with the resource polymorphism that has been observed for other lake trout populations and other char species.