The Tasmanian Trout Fishery. IV. The Rivers of the South and South-East

Abstract

Two main river systems are included in this region, the Derwent and the Huon. Data derived from anglers' returns are analysed for each system separately but those from the Huon are insufficient for a thorough study. There is some doubt as to the representativeness of returns from either system. No significant changes have been found in the fishery over a period of 12 seasons either in the rate of daily catch per angler or in the length of fish taken. A study of the fish taken in an upstream trap at spawning time yields an annual mortality rate of about 60% for the Derwent River System and recaptures of tagged fish show a similar rate. Population estimates based on recaptures of tagged fish and on the spawning potential within the system indicate a total population of between one- half and one million, of which about 20% is of takable size. The contribution made by the release of hatchery-reared fish is shown to be insigniiicant. Evidence is produced which leads to the conclusion that there may be two distinct races of trout in Tasmania, the result of separate introductions of river and sea trout, distinguished by inherent meristic differences as well as by differences in growth rate and habits.