Mass artificial incubation of redclaw crayfish eggs in a recirculating mechanical pulling device

To solve the problems involved in the mass artificial incubation of redclaw crayfish eggs, we developed a recirculating mechanical pulling device to explore the technology of artificial incubation, including the egg stages, egg densities, attachments and incubator sizes. The eggs were separated and sterilized with 3000 ppm formaldehyde, and the water temperature was 28–29°C. The results were obtained: (1) the hatching rates or survival rates of the groups with 7 pairs of appendages and well-formed eye pigments were significantly higher than those of the egg-nauplius group; (2) the hatching rates of eggs incubated at densities of 300 eggs/incubator box were significantly higher than those of eggs incubated at 700 eggs/incubator box. The survival rates of eggs incubated at densities of 300 or 500 eggs/incubator box were significantly higher than those for eggs incubated at 700 eggs/incubator box; (3) the survival rates of the group whose incubator received a sponge attachment were significantly higher than those of the group without a sponge attachment; (4) the survival rates of the group with 2.5- or 3-cm width of the upper end of boxes were significantly higher than those of the group with 4 cm; and (5) the eggs with 7 pairs of appendages or well-formed eye pigments were selected, with a density of 300–500 eggs/incubator box, and the box was 2.5-cm wide at the upper end. After hatching, sponge attachments were inserted. The hatching rate and survival rate were 85.34% and 61.31%, and a total of 240,031 specific pathogen-free seedlings were cultivated.