The paedogenetic male cycle in Salmo salar L

Abstract

In a paper in 1938 we, along with G. M. King, gave an account of the ripe male sexual phase in salmon parr from the Welsh Dee. In this paper it was shown that the attainment of the ripe male phase is normal in at least a high percentage (about 80%) of the male population, and not merely in a few individuals. This work was complementary to that of Carr (1913), Dahl (1910) and others (vide Tchernavin 1939), and extended and clarified their observations. It was also shown that among migrating fish (smolts) there were (1) males with apparently spen gonads, (2) the normal females with immature gonads, and (3) individuals with tubular gonads extending the length of the body cavity. Some doubt was felt about the sex of fish with long tubular gonads, but they were thought to be and have now been proved to be males, thus confirming Carr’s assumption ( loc. cit .). Most of these tubular gonads are immature and virgin. The problem remained whether in fact young males spawn on the beds before migrating to the sea. It was noted that many statements in the literature affirmed that this occurred, but no critical observations appear to have been made. At the present time we consider that the only scientific evidence we have on this matter is circumstantial and is supplied in the observations recorded below.