Area of Distribution, Movements, Age Composition and Mortality Rates of the Australian Salmon Population in Tasmania, Victoria and New South Wales

Abstract

Two subspecies of the Australian salmon, a perciform fish, occur in eastern Australian waters.

The western subspecies, Arripis trutta esper (Whitley), is found only in Tasmania and Victoria. In Tasmanian waters fish do not occur above an age of 2+ years. In Victoria about 300 000 fish (180 tonnes) of an age range from of to 5+ years are caught annually. The younger age groups are found in sheltered areas, and the older age groups along the open coastline, especially in western Victoria.

Returns of tags from fish thought to be of the western subspecies indicate that movement towards Western Australia takes place via western Victoria and South Australia, rather than by a direct seawards movement.

For the eastern subspecies, Arripis trutta marginata (Cuvier & Valenciennes), young fish from 0+ to 2+ years are found predominantly in Tasmania and Victoria, and older fish from 4+ years in New South Wales.

Recaptures of tagged fish indicate that there is a continual movement at all stages of the life cycle from Tasmania to Victoria and then to New South Wales. Fish within New South Wales also show evidence of a movement southwards, which probably occurs only once, to the eastern Bass Strait area. Fish older than 5+ years move increasingly northwards in New South Wales waters.

For the eastern subspecies estimates of M, the instantaneous annual natural mortality coefficient, range from 0.5 to 1.0, and estimates of F, the instantaneous annual fishing mortality coefficient, range from 0.3 to 0.7. It is suggested that in the present eastern subspecies fishery greater yields should result from increasing the fishing pressure up to about twice the present value.