Rearing of Cherax quadricarinatus (Von Martens, 1868) juveniles using feed for sturgeons

At present, the Australian red-clawed crayfish Cherax quadricarinatus (Von Martens, 1868) farming is not well-developed and is mainly limited to temperate and subtropical regions where the initial stages of growth occur under well controlled conditions. In Russia, C. quadricarinatus farming technologies are under development and the values of bioproducts are much more lower. Juveniles of crayfish are more demanding on feed and require at least a 30-50 % protein-based diet for rapid growth. Starter feed for sturgeon fish species has the appropriate indicators, which opens up prospects for its use in crayfish farming. In this work, for the first time, we submit data on feeding norms, growth rate, survival and hematological indicators of juvenile crayfish fed sturgeon feeds with a protein content of 46 %. Scientific research was aimed at studying the parameters of hemolymph and growth of juvenile Australian red-clawed crayfish that received mixed feed for sturgeons. The experiments were conducted at the Kuban State University. Equal-aged 480 juveniles of Australian red-clawed crayfish with an average weight of 150 mg were selected from three females, mixed, and distributed in three rearing tanks of 160 individuals each, according to feeding rates (group I - 9 %, group II - 6 %, group III - 3 %). The tnaks were mounted in a multi-tiered closed aquaculture system. The crayfish juveniles were fed twice a day (in the morning at 900 and in the evening at 1800) with granulated feed Сoppens vital (0.8-1.2 mm) (Alltech Coppens B.V., the Netherlands), a protein content of 46.0 %. Survival rates and growth rates were recorded every 8 days (July 21, July 29, August 6, August 14, and August 22). A dayly feeding rate was adjusted with respect to changes in survival and biomass of the groups. On day 32, 13 individuals weighing from 0.67 to 1.39 g were selected, boiled and weighed separately. The meat was separated from the carapace and other inedible parts and weighed. To determine the total hemocyte counting (THC) and the proportion of granulocytes in the hemolymph of crayfish, the cuticle was pierced at the base of the first pair of pleopods from the ventral side of the first segment of the abdomen and a small amount of hemolymph was removed with a micropipette. At the end of the experiment, the median length was 3.50 cm for groups I and II, 3.40 cm for group III; the median weight was 0.94 g, 0.98 g, and 0.89 g for groups I, II, and III, respectively. The differences between the groups were statistically insignificant. The final mortality was 57 individuals (35.6 %) for group I, 62 individuals (38.7 %) for group II, and 58 individuals (36.2 %) for group III. Differences between the groups in total hemocyte counts (THC) and percentage of granulocytes were statistically insignificant. The THC average values ranged from 1005 to 1073 cells/ml, granulocytes accounted for 20.1 to 21.1 %. The median THC was 965 cells/ml for group I, 840 cells/ml for roup II, and 1101 cells/ml for group III; the median percentage of granulocytes was 21.1 %, 20.1 %, 20.6 %for groups I, II, and III. The THC values at different daily feeding rates does not depend on the percentage of granulocytes (the correlation coefficients ranged from -0.02 to -0.08). The relative weight gain decreased from 99.8 to 17.6 % (group I), from 102.6 to 19.1 % (group II), and from 105.4 to 16.9 % (group III). The specific growth rate was from 8.6 to 2.0 % (group I), from 8.8 to 2.2 % (group II), and from 9.0 to 2.0 % (group III). The meat yield index of crayfish juveniles did not differ significantly between the groups. Average indicators ranged from 31.1 to 32.5 %. In group I, the feed cost was the highest, 2.00 vs. 1.47 in group II and 0.72 in group III. Low feed consumption (daily feeding rate 3 %) with similar values of growth rates, survival rates, average weight and length, and their medians indicate efficient assimilation of feed by C. quadricarinatus juveniles in group III and excessive feeding rate in other groups.