Field Performance of Triploid and Diploid Rainbow Trout in South Dakota Ponds

Abstract Triploid fish theoretically divert energy from sexual development and reproductive behavior into somatic growth. We found lengths, weights, and relative weights of triploid rainbow trout Oncorhynchus mykiss to be significantly (P ≤ 0.05) less than those of diploid fish at the age of 45 months in three South Dakota ponds. Gonadal development in triploid females was negligible in 1989 and 1990 and reduced in triploid males during 1990. Catches of triploid fish were always lower than catches of diploid fish, suggesting lower survival. Physiological factors, perhaps environmentally induced, may have diminished the growth potential of triploid rainbow trout. Results of this study indicate that the use of triploid rainbow trout is not justified as a means of obtaining increased growth and survival under the conditions present in our study ponds.