Reproductive cycles in the eastern subspecies of the Australian salmon, Arripis trutta marginata (Cuvier & Valenciennes)

Abstract

To complement similar work carried out on the western subspecies of the Australian salmon (Arripis trutta esper), the known data on the reproductive cycle of the eastern subspecies (A. t. marginata) are summarized.

The data (collected between 1961 and 1963) consisted of ovary and testis welghts, fish lengths, oocyte diameters from preserved ovaries, and information from histological material.

The gonad weight data were analysed to show increases in ovary and testls weights, which were indicative of sexual activity. Supporting information was extracted from changes in maximum oocyte diameters, and from examination of histological sections.

The onset of sexual maturity for juvenile fish in Tasmanian waters occurred at a length of approximately 39 cm (equivalent to the end of the fourth year of life). The corresponding length for the western subspecies is 54 cm (at approximately the same age), and 52-54 cm for New Zealand fish. There was no evidence of spawning activity in Tasmanian waters.

Cycles of sexual activity were observed in fish from the Lakes Entrance area of Victoria and the Eden and Bermagul areas of southern New South Wales.

Spawning activity was deduced to occur between December and January in the Lakes Entrance area, between January and February in the Eden area, and between November and February in the Bermagui area. Sexual maturation may commence in males at a slightly younger age than in females.