Maturity and fecundity of Champsocephalus gunnari, Chaenocephalus aceratus and Pseudochaenichthys georgianus in South Georgia and Shag Rocks Islands

The reproductive biology of three species of icefishes (family Channicthyidae), Champsocephalus gunnari, Pseudochaenichthys georgianus and Chaenocephalus aceratus in South Georgia and Shag Rocks Islands was studied by means of a histological analysis. Parental care, a widespread behaviour among icefishes such as C. aceratus, is not observed in C. gunnari, which has a broadcast spawning strategy. There were large differences in total fecundity mainly due to the different sizes reached by each species (total fecundity range was 2,500-21,300 hydrated oocytes). Nevertheless, when comparing relative fecundity values, the average results were, in general, similar for P. georgianus and C. aceratus (6-9 hydrated oocytes per female gram). However, relative fecundity estimated for C. gunnari was 10-37 hydrated oocytes per ovary-free female gram. The difference may be a consequence of the smaller oocyte size of the species as compared to other icefishes. The small diameter of hydrated oocytes was also associated with low values of dry weight. The high relative fecundity recorded for C. gunnnari may compensate, in part, for a broadcast spawning strategy.