Redclaw crayfish aquaculture

Market and industry

Redclaw crayfish have biological characteristics that give them an advantage in aquaculture:

• fast growth
• the ability to breed naturally in ponds
• a simple life cycle
• redclaw can be sold live, cooked or frozen.

In Queensland, the industry is well developed and redclaw are relatively economical to produce due to simple production systems and natural breeding. Queensland redclaw crayfish are recognised both domestically and internationally as a safe and healthy product.

Contact the Queensland Crayfish Farmers Association for advice and support.

View the annual aquaculture industry report for the latest valuation and production data.

Culture and production systems

The natural habitat of the redclaw is turbid billabong that is flushed during the wet season, however commercial grow out is done in earthen ponds.

Ponds range in size from 1,000 to 1,200 metres squared (m²) with sloping bottoms (1.3–1.8m deep) for easier drain harvesting. Juvenile crayfish of similar size are stocked in prepared ponds at 5–15 animals per square metre. Stock and pond water must be carefully managed to maximise growth and animal health.

Water temperature

• An ideal site will be above 23°C during as much of the year as possible.
• Optimal growth takes place between 26°C and 29°C.
• Deaths occur in cold and hot extremes of 9–10°C. and 34–35°C.

Water quality

Redclaw can survive under conditions that would normally kill other species, but their pond water still must be carefully managed. For maximum growth and good economic returns, follow best–practice protocols for managing water in earthen ponds.

Redclaw tolerate very low oxygen levels, but the dissolved oxygen level should be kept above 5ppm. If dissolved oxygen in the pond water drops below 1ppm, redclaw move to the edge of the pond where oxygen levels are higher. Extremely low oxygen will cause crayfish to migrate from the pond over land.

Salinity (salt) levels in pond water that regularly exceed 2 parts per thousand (ppt) will impact growth and behaviour.

The ideal pH range for redclaw is 7–8.5. Moulting and and hardening of the redclaw’s shell can occur if:

• the pH level of the water is less than 7
• calcium levels are low, with a hardness of less than 50 parts per million (ppm).

Breeding

Successful redclaw breeding depends on water temperature and hours of sunlight each day. Crayfish naturally breed between September and April. You can lengthen the breeding period in a controlled environment by adjusting the temperature to simulate the onset of the breeding season.

Techniques for breeding and juvenile production vary considerably between farms and regions. Generally, selected broodstock (redclaw strains that are clearly superior for cultivation over others) are placed in specially designed ponds or tanks and mating happens naturally.

The female broods the eggs for 6–10 weeks, depending on temperature. The larger the female, the more eggs she can produce. Most females produce 300–800 eggs per brood. Redclaw may produce 3–5 broods during the breeding season.

Hatchlings resemble adults and remain attached to the underside of the female for several weeks before progressively becoming independent of the mother.

Advanced juveniles are normally harvested at 5–10g (3–4 months old) and sorted for size and sometimes sex.

Feeding and growing

The total grow out time in earthen ponds is about 6–9 months (plus the 3–4 months spent in the juvenile production pond). Stock is often harvested progressively due to differential growth rates. Several market size grades exist from 35g to over 100g.

Shelter

Like all crustaceans, redclaw moult or shed their shell as they grow. Immediately after moulting, redclaw have soft shells and are vulnerable to predation by other crayfish in their pond.

Providing shelter increases the survival and growth potential of farmed redclaw. The best forms of shelter are mesh materials, such as onion bags or shadecloth, and short lengths of pipe.

Feeding

Feeding is normally undertaken 3 times a week just before dusk to coincide with the animal's peak foraging behaviour. Some form of aeration is normally installed (usually airlift pumps) to increase the carrying capacity of the ponds.

Feeding of formulated pellets is often supplemented by a mixture of grains to provide a basic food base for the animal, although much of the nutritional requirements can be obtained from natural pond production (e.g. plankton, bacteria, protozoans). This natural production can be enhanced by organic and inorganic fertilisation, as long as ammonia (<0.05mg/L) and oxygen levels (>5.0mg/L) remain within the acceptable range.

Harvesting

Redclaw farmers use several harvesting techniques, either independently or together:

• bait trapping
• drain harvesting
• flow trapping.

Flow trapping is the most successful of these because it takes advantage of crayfish's natural behaviour. During flow trapping, a current of water is directed into the pond through a ramp. This causes the crayfish to join the current, flow up the ramp and into a harvest box.

You must drain and dry every pond at least once a year to effectively manage the environment and redclaw stock within the pond. After the harvest, the best crayfish are chosen for use as broodstock, the rest are sold. Desirable criteria for broodstock includes:

Select broodstock that show a fast growth rate to help pass this gene to successive generations.