Growth and maturation rates of hatchery reared juvenile rainbow trout (Salmo gairdneri, Pennask Lake stock) were compared in two groups of fish sorted into three size classes (small, < 7 mm; medium, 80-94 mm; large > 115 mm). One group consisted of progeny from four-year-old Virgin spawners (selected) and the other, from the annual egg collection conducted by Summerland Trout Hatchery (unselected) from mainly 3 yr old spawners. Trout were reared in a hatchery from May 5 to October 29, 1984 at 15 degrees C with a food ration of 2% of body weight per day under simulated natural photoperiods. For selected and unselected groups combined, the proportion of mature males averaged 1.7%, 10.9% and 49.2% for the small, medium and large size classes, respectively. Grading is suggested as a technique to decrease the number of precocious males being stocked into quality lakes. There were no significant differences in male maturation rates between the selected and unselected groups for the three size classes.
Tsumura, Kanji, Hume, Jeremy M.B.. 1986. A Comparison of Precociousness in Three Graded Size Classes of Hatchery-reared Rainbow Trout (Salmo gairdneri). Ministry of Environment and Parks. Fisheries Technical Circular. FTC75
Topic: Fish and Fish Habitats
Keywords: rainbow trout, Salmo gairdneri, Pennask Lake stock, growth, maturation, hatchery, sex ratios, grading, management, stocking
Scientific Name: Oncorhynchus mykiss
English Name: Rainbow Trout
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