Reproductive aspects of Galaxias platei (Pisces, Galaxiidae) in a deep lake in North Patagonia

Abstract

Reproductive characteristics of the native fish Galaxias platei were studied in Lake Moreno, an ultra-oligotrophic deep lake in North Patagonia. According to histological analysis of ovaries, G. platei presents synchronous oocyte development typical of a group-synchronous spawner. Mature oocyte diameter ranged from 1031 to 1419μm. Based on the gonadosomatic index, annual spawning occurs between April and June (austral autumn) and is directly related to the water temperature of deeper strata (below 30m) where this species lives, but not with photoperiod. Female G. platei acquire sexual maturity at a length of 105mm, whereas males acquire sexual maturity at a length of 177mm. Delaying maturity to obtain higher fecundity, as well as maximum body size and longevity, indicates that G. platei is more specialised than the other South American Galaxias, G. maculatus, in terms of lifestyle. These specialised features are related to the stable environment G. platei lives in and indicate that it could eventually become a vulnerable species in unstable environments, such as the Patagonian lakes dominated by salmonids.