Relative Survival and Growth of Triploid and Diploid Rainbow Trout in Two Idaho Reservoirs

Abstract The objective of this study was to determine whether triploid rainbow trout Oncorhynchus mykiss grew faster or lived longer than diploid rainbow trout stocked in two southeastern Idaho reservoirs. In October 1996, triploid and diploid rainbow trout were differentially marked and stocked in equal proportions. Relative survival and growth rates were estimated by means of gill-net and electrofishing samples collected through October 2000. In both reservoirs, the relative survival rate (total catch) was significantly higher for triploid fish. The final catch ratios (triploid: diploid) were 1.4:1 and 1.9:1 in the Treasureton and Daniels reservoirs, respectively. We also observed ontogenetic differences in growth. At age 1, mean lengths and weights were similar for the triploid and diploid fish in each reservoir. During the second year, diploids weighed significantly more than triploids. The trend reversed as the diploid fish matured: age-3 and older triploids matched or exceeded diploid fish in length...