LAUSR

ABSTRACT A comparative study was conducted on gonad development of triploid Salvelinus fontinalis, Salvelinus umbla, and Salmo trutta f. lacustris. Triploid males developed testes and had a reproductive cycle similar to the diploid controls. In triploids the GSI peak during spawning was reduced. Testicular germ cells differentiated to spermatozoa most of which degenerated in the seminiferous tubules. Two years old triploid males did not spermiate, while <15% of 3 years old males produced semen. In non-male triploid S. fontinalis and S. trutta f. lacustris gonad development was delayed as 2 years old fish did not differentiate gonads. Three years old fish developed hermaphroditic gonads. In 2 years old triploid S. umbla about 40% of non-male fish developed ovaries with GSI values similar to diploid controls. The other 60% of fish developed sterile gonads containing no germ cells. The results demonstrate that gonad development in triploid salmonids is species and age specific.