Growth performance comparison of intercross-triploid, induced triploid, and diploid rainbow trout

Use of all-female triploids (3N) instead of diploids (2N) can be advantageous in rainbow trout (Oncorhynchus mykiss) aquaculture and fisheries management due to sterility and the consequent superior growth and feed conversion achieved at reproductive age. Triploid trout are currently produced by pressure or temperature shock of the zygote (induced-triploid, 3NP). An alternative procedure to create triploids that may have fewer negative effects on embryonic development and result in 100% triploids is to mate a tetraploid (4N) parent with a 2N parent (intercross-triploid, 3NC). We compared growth performance of nine sets of families each consisting of 3NP, 3NC, and 2N siblings through two years of age. The 2N and 3NC fish exhibited greater body weight than the 3NP fish throughout most of the study; however, by the end, body weight of the 3NC fish exceeded that of the 2N and 3NP fish, which were similar. Condition factor was lowest for 3NC and highest for 3NP fish throughout most of the study. Higher rates of vertebral compression in the 3NP fish affected body weight, fork length, and condition factor in this group. The correlations of body weight among families for the three ploidy types ranged from R-2 below 0.03 around 8-9 months post-hatch, to above 0.5 around 1819 month post-hatch, supporting family differences in growth response to triploidization and triploidization strategy. Nevertheless, a greater correlation between 2N and 3NC values than 2N and 3NP values, particularly at body weights above 11 kg, supports greater potential to improve 3NC growth performance compared to 3NP performance when genetic selection is based on the 2N phenotype. Published by Elsevier B.V.