Trout Aquaculture Potential

Trout have been successfully farmed internationally for hundreds of years and for over 50 years in Western Australia, and the Department of Fisheries has fostered trout farming through the SWFRAC for many years. Consequently, the biology, nutrition, culture requirements and diseases of both rainbow and brown trout are well understood.

Unlike many other candidate species for aquaculture in Western Australia, trout farming is not limited by availability of artificial diets, supply of juveniles or equipment. Trout also have an established market acceptance both locally and internationally and have demonstrated potential for value-added products such as paté or smoked trout. Culturing trout for recreational fishing is a well-established tourist industry in WA and throughout the world.

Hatchery Improvements

Improvements at the trout hatchery at the SWFRAC have made it a more reliable producer of trout eggs, fry and yearlings. Annual production capacity at SWFRAC has now expanded to more than one million fry and it could be useful to new entrants into trout farming in WA before they establish their own hatcheries.

Trout farmers in WA currently operate within a protected industry as, due to concerns regarding the introduction of diseases, bans exist on the importation of live or fresh trout products from overseas into WA.

Quarantine

However, a review by AQIS (the Australian Quarantine and Inspection Service) on the importation of trout and trout products is currently underway and has recommended that the importation ban be lifted for some consumer-ready fresh salmonid products. The ban on live salmonids remains.

Selective Breeding

Due to selective breeding over at least 40 years, trout are the only fish species currently cultured in WA which could be called domesticated. Generally, domesticated stocks of species perform better in production situations as they are selectively bred for favourable traits (such as higher and more uniform growth rates) and local conditions (such as temperature tolerance).

Due to the length of time that stocks have been maintained within WA, the current strain of rainbow trout demonstrate improved upper limit temperature tolerances. This is critical given the temperature and water requirements of trout and the high summer temperatures and generally low water availability in most areas of WA. Trout stocks in WA are also relatively disease-free.

Wild Population Control

Unlike some other introduced species from the eastern States or overseas, it is difficult for trout to establish breeding populations in natural waterways due to the lack of suitable spawning environments. This has been demonstrated over a period of more than 50 years in Western Australia, with few instances of trout spawning being recorded in the wild.

This is an important consideration as it allows the control of trout populations by controlling the number of fish stocked for recreational fishing opportunities. Any escape of trout from aquaculture situations is not likely to result in the establishment of extensive wild populations.

Non-reproducing fish are also a benefit to trout producers as more energy is put into growth instead of gonad production and reproduction, resulting in higher growth rates. Although trout are an introduced species, due to the long time that they have already been stocked in WA water bodies, they are unlikely to have any unexpected ecological or environmental impact in the future. A review on the effects of salmonid translocation in WA is currently underway by Chappell (in prep).

Farm Production

Farm productivity relies upon site selection factors (temperature, reliability, availability and quality of water supply), system design factors (effluent removal and holding capacity) and husbandry (feeding regimes, particularly in relation to dissolved oxygen levels). The readily-available data for trout production makes it possible to estimate potential farm production capacity, given water temperature and minimum summer water flows.

The major factors limiting trout production in WA are warm water temperatures throughout much of the state and the unavailability of large volumes of cool water during summer. Further, the generally modest scale of operation can limit competitiveness against interstate suppliers.

Due to environmental constraints, trout farms in WA are largely restricted to the cooler south-west corner of the State. The solution to this limitation may lie in obtaining access to supplies of cooler water, such as by permitting access to irrigation schemes in the south-west, particularly if water supplies are affected by salinity increases and are of less use to agriculture.

Current initiatives include the assessments of performance of yearling trout grown in cooler periods of the year in saline farm dams, and the potential for further improving the tolerance of local trout populations to high temperature by selective breeding programmes.

More detailed information on the economic viability of trout farming in Australia is available by Treadwell et al. (1991) and Gooley (1998).

Informtation courtesy of the WA Department of Fisheries