Publication Date

1-1990

Series Number

92

Publisher

Fisheries Department of Western Australia

City

Perth

ISBN

0 7309 1744 4

ISSN

1035-4549

Abstract

This report presents information on the probable original introduction of the eastern Australian yabbie to farm dams in the Wheat-belt Region of the southwest of Western Australia (in 1932 at Narembeen); the probable type of yabbie (the "White Yabby", Cherax albidus Clark 1936 ) and source (Miram Swamp in the Victorian Wimmera); and, in 1985, the first voicing of concern over the spread of yabbies to natural habitats, particularly in the higher rainfall region of the southwest, together with current national and international concerns and advice on introduced aquatic species.

Commercial harvesting ("extensive" aquaculture) of existing yabbie stocks in wheat-belt farm dams commenced in the mid 1980s and has produced an increasing annual catch, which attained 17 tonnes in 1989. The Fisheries Department has confined commercial operations, by licensing, to the drier, mainly wheat-belt, areas east of the Albany Highway, linking Perth and Albany; and to north of Perth. One of three departmental initiatives to examine the advisability of lifting this geographic restriction, requested by yabbie farmers, was to carry out a brief field survey, reported here.

The incidence of yabbies in farm dams was found to have increased since 1985 in the parts of watersheds just to the west of the Albany Highway. Associated sampling in adjacent rivers showed that no yabbies were present due to high salinities. Three more coastal (less saline) locations also showed no penetration of streams by adjacent farm dam stocks. Yabbies have been established for many years in some farm dams to the west of the Albany Highway, in some instances up to 25 years. In the more northerly Indian Ocean Drainage Division, the Hutt and Bowes Rivers north of Geraldton have stocks of yabbies, with introduced marron also present in the Hutt River, and other introductions are reported through this Division. Farther north, the Timor Sea Drainage Division in Western Australia, i.e. in the Kimberley Region, has no native crayfish and introduction of the yabbie or the Queensland red claw (C. quadricarinatus) has not taken place, as yet.

Very few farmers (2 of 55) interviewed during the southwest survey were aware that the yabbie is an introduced species. The misnaming of the yabbie as the koonac, the common name of some species of native crayfish, was frequent. The recent availability of a departmental identification leaflet with colour photos of the species is intended to correct this misapprehension.

Ecological barriers to the penetration of yabbies into natural habitats in the southwest are considered in terms of the yabbie's known tolerances for temperature, oxygen and salinity, the source habitat and hence ecotype of the yabbie strain which is present in Western Australia as indicators of preadaptation, the seeding densities of yabbies escaping from dams to streams, and predation and competition from resident fish, crayfish and bird species. The yabbie is very unlikely to spread to the ephemeral winter/spring surface water habitats (swamps and tributaries) of the native burrowing crayfishes because of its summer breeding and growth dependent lifecycle.

Factors favouring the spread of yabbies are also considered, particularly for the lower reaches of rivers and large public dams supporting the recreational marron fishery. In the medium to long term any further eutrophication of the rivers will favour the invasion of yabbies, so long as salinity does not reach unfavourable levels for them.

The scope for geographic location and expansion of yabbie farming is examined. Extensive production by harvesting from farm dams is dependent on large areas of dam waters and, therefore, has more scope in the higher rainfall area of the southwest. However, the annual crop may be limited unduly by lower water temperatures, and by bird predation and low catchability in the clear water conditions of gully dams, there.

In terms of both conservation issues and worthwhile additional production, any areal expansion of the present extensive harvesting of yabbies and, more especially, development of semi-intensive farming are best located in the warmer, near coastal, region north of Perth.

Number of Pages

33

Keywords

Yabbie (Cherax albidus Clark, 1936), Introduced species, Farm dams, Western Australia

Disciplines

Aquaculture and Fisheries | Management Information Systems | Management Sciences and Quantitative Methods | Natural Resource Economics | Natural Resources and Conservation | Population Biology | Sustainability | Terrestrial and Aquatic Ecology

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