Redclaw is a tropical species endemic to north-west Queensland and the north-east of the Northern Territory. The harsh physical extremes of this distribution have given redclaw a robust nature with broad climatic tolerances.
Its preferred temperature range (water temperature) for >70 percent of maximum growth rate is 23ºC to 31ºC. Temperature extremes beyond which redclaw will perish are 10ºC and 36ºC.
Reproduction will only occur while water temperature remains above 23ºC. While suitable temperatures prevail throughout Queensland during summer, the shorter and less extreme winter period in more northern areas confers a significant advantage.
Most industry growth is expected to occur north of Bundaberg, including parts of western Queensland, northern Northern Territory and the Kununarra region of Western Australia.
Redclaw aquaculture necessitates earthen ponds which hold water. Consequently, soil must have a reasonable clay content and be free of rock. Ponds are typically 1,000 sq.m in surface area, with a depth of between 1.0 and 2.5 m. Their specification and design can have an important bearing on productivity, so professional advice should be sought prior to construction.
Productive topsoil can be beneficial when applied across the clay-base of a pond, but it must be free of pesticides which may be highly toxic to crayfish. Water may be sourced from surface supplies or underground. Generally, water suitable for watering livestock is suitable.
Some of the characteristics which should be identified include;
- pH of between 6.5 and 8.0,
- hardness of >40 ppm,
- low salt content
- and low metals content.
Once water has been introduced to the production ponds there are a host of management issues which must be addressed to ensure optimal water quality for redclaw production.
Further information on water quality management should be sought. Water usage is dependent on local evaporation rates, but will range from 15 to 20 megalitres per hectare of ponds. This is on the basis that all effluent from harvested ponds is recycled through appropriate settlement and supply dams.
Research has demonstrated that distinct strains of redclaw occur throughout the species natural range. The differences between strains are generally slight, however, variability of biological characteristics as borne out in production statistics suggests that some strains are superior for aquaculture purposes. Although the full range of strains have not been assessed, it is clear that the Gilbert and Flinders River strains have advantageous characteristics in regard to high fecundity (number of young per brood) and fast growth rates at high densities.
Some long-standing redclaw farmers have selectively bred their perceived 'best' crayfish and cross-bred strains to improve their stock. There are clear indications that these improved stocks are superior to wild undomesticated stock and to stock from farms where managed reproduction has not occurred.