Juvenile Redclaw Research Articles

Production of juvenile redclaw crayfish, Cherax quadricarinatus (von Martens) (Decapoda, Parastacidae) III. Managed pond production trials

Commercial-scale production of juvenile redclaw crayfish was conducted in earthen ponds. Based upon the results of previous experimental studies in tanks and aquaria, earthen ponds (1300 and 2600 m 2) were furnished with juvenile crayfish shelters, and were prepared and managed to maximise availability of zooplankton. Juvenile redclaw were introduced by stocking ponds with egg-bearing females. Stocking density, as expressed by number of fertile eggs introduced, ranged from 74 to 326/ m 2. Ponds were harvested after culture periods ranging from 45 to 62 days. Juvenile number at harvest ranged from around 6000 to over 36 000, representing a mean of 63.2 juveniles per maternal survivor. Mean size at harvest ranged from 0.31 to 1.00 g, representing growth of 9.7 to 36.9 mg/day. Results suggest that managed pond production of juvenile redclaw is commercially viable at the production rates achieved, and that a considerable increase in productivity is possible with increased availability of shelter and improved zooplankton management techniques.

Production of juvenile redclaw crayfish, Cherax quadricarinatus (von Martens) (Decapoda, Parastacidae) I. Development of hatchery and nursery procedures

Procedures were developed for the controlled production of juvenile redclaw crayfish, Cherax quadricarinatus in tanks over two seasons. These included broodstock handling methods and involved the definition of an in vivo ovary staging technique which permitted recognition of immature, maturing and mature females. Hatchery techniques were also defined which demonstrated that male:female ratios of up to 1:4 were equivalent for successful mating and spawning. Up to 97% of females spawned and carried eggs through to hatching when held in tanks at between 24.5 and 27.6 °C mean daily temperature and exposed to 14:10 hours light:dark day length. A sequential series of seven egg stages was defined from egg release through to hatching, based on morphological characteristics. The mean duration of each stage was measured and cumulative statistics calculated, indicating a mean incubatory period of 72.1 days (range 47 to 84) and 66.3 days (56 to 71), respectively, for the two hatchery runs. An exponential function was calculated which defines the relationship of fecundity and female size and which indicates that fecundity ranges from approximately 200 to 1000 eggs per female. Nursery procedures were developed which indicate difficulties with using the floating water plant Pistia as juvenile habitat, and the benefits of using artificial shelters. Newly hatched juveniles stocked at between 980 and 1842 m 2, and fed a combination of formulated flake food and fresh zooplankton, survived well (mean 52%) and increased in size by between 500 and 900% over 28 to 50 days. The research demonstrates that C. quadricarinatus can be easily bred in captivity and juveniles reared successfully with relatively simple facilities and techniques.

Juvenile growth performance among stocks and families of red claw crayfish, Cherax quadricarinatus (von Martens)

A laboratory comparison of the growth performance of juvenile red claw crayfish ( Cherax quadricarinatus) was conducted in relation to stock and family. For stock comparison, body weight at ages during the first 84 days after release was measured for juveniles of the first generation derived from three river systems in northern Queensland, Australia: Weipa, Gilbert and Mitchell. Although the body weight of newly released juveniles was similar for the three stocks, a significant difference among stocks in body weight was shown at all post-release ages measured except at 28 days. Furthermore, the stock component of growth performance variation increased with age. On the other hand, the family component of growth variation decreased with age within all three stocks. A further study of the second generation progeny of the Gilbert River stock further demonstrated a substantial genetic component of growth performance variation in this species. Heritability estimates, based on full-sib intraclass correlations, were 0.72 ± 0.14 at 30 days, 0.48 ± 0.10 at 60 days and 0.32 ± 0.31 at 90 days after release.

Heat and oxygen flux as a function of environmental po2 in juvenile Australian crayfish, Cherax quadricarinatus

AbstractOxygen and heat flux of the juvenile Australian red claw crayfish, Cherax quadricarinatus, were measured in parallel respirometry and calorimetry systems at 28°C at varying levels of environmental po2. Juvenile crayfish maintained an average oxygen flux of 5.0 ± 0.4 (SEM) pmol O2/(s*mg fresh weight) over the po2 range from 20.7 to 5 kPa. At approximately 4 kPa po2, oxygen flux decreased, conforming to decreasing oxygen tensions. Juvenile crayfish maintained an average heat flux of −2.2 ± 0.2 μW/mg fresh weight when exposed to 100 and 50% air saturated conditions (18.1 to 20.7 and 7.8 to 10.4kPa po2, respectively). The ratio of the amount of heat dissipated per oxygen consumed, called the calorimetric/respirometric (CR) ratio, at 100 and 50% air saturated conditions averaged −440 kJ/mol O2. When crayfish were exposed to 25% air saturated conditions (2.5 to 5.2 kPa po2), heat flux decreased initially to −1.1 ± 0.4 μW/mg fresh weight. Within 4 hr, however, heat flux returned to normoxic values. When crayfish were exposed to anoxic conditions, heat flux decreased to zero. Most juvenile crayfish did not survive short‐term (1–2 hr) anoxic stress. These data suggest that juvenile C. quadricarinatus are excellent oxygen regulators over a wide range of environmental po2. These data indicate also that juvenile C. quadricarinatus can compensate metabolically, possibly via aerobic and/or anaerobic adjustments, in order to maintain metabolic rate at critically low po2. Last, this crayfish appears limited in its ability to utilize anaerobic pathways to maintain metabolic rate in anoxic environments. © Wiley‐Liss, Inc.

Preliminary Pond Production of the Red Claw Crayfish,Cherax Quadricarinatus,in the Central United States

The Australian red claw crayfish, Cherax quadricarinatus, has recently attracted attention as a potential candidate for aquaculture in the United States. This paper reports the first experimental yield trials of the red claw crayfish in the central United States. Two earthen ponds (0.30 and 0.31 ha) were stocked with juvenile red claw crayfish at either 3.5 or 7.0 crayfish/m2. Crayfish were fed a diet of pelletized shrimp ration supplemented with corn silage. When stocked at 3.5/m2, red claw crayfish grew from an average weight of 3.0 g to 27.0 g in 97 days; average survival was 79.6%; net yield was 653 kg/ha; and feed conversion was 1.4. When stocked at 7.0/m2 red claw crayfish grew from an average weight of 4.1 g to 19.7 g in 99 days; average survival was 70.0%; net yield was 678.9 kg/ha; and feed conversion was 1.8. During the yield trial, temperatures were optimal for growth (25 to 33°C) 60% of the time. These findings are sufficiently encouraging to warrant further trials in locations with a longer g...