Selection of suitable stocking densities of Procambarus clarkii in the environment of Elodea nuttallii.

To investigate the suitable stocking density of red swamp crayfish (Procambarus clarkii) in an environment with about 60% Elodea nuttallii coverage rate, a 45-day rearing experiment was conducted. The initial weight of juvenile crayfish was (4.35±0.95) g, the growth performance, food source contribution and non-specific immune enzyme activity of red swamp crayfish were compared at different stocking densities (10, 15, 20, 25 and 30 ind. /m²). The results showed that: The final body mass, terminal body length and weight gain rate of crayfish in the density group of 10 ind./m² were the highest, and there was no significant difference among the other groups, and the culture density was higher than 15 ind./m², the proportion of small-sized crayfish (10-15 g) increases significantly; The average food source contribution of Elodea nuttallii to crayfish ranged from 12.8% to 26.9%, and its contribution to large-sized crayfish (20-25 g) was higher than that of small-sized crayfish; There was no significant difference in the activities of superoxide dismutase (SOD) and lysozyme (LZM) among all groups, the malondialdehyde (MDA) content of crayfish of only 10 ind./m² was significantly lower than the other four groups, which indicated that ensuring certain coverage rate of Elodea nuttallii can effectively reduce the negative effects of density stress, and the intake of Elodea nuttallii could have a positive effect on the non-specific immunity of crayfish. In conclusion, the suitable stocking density of crayfish was 15 ind. /m² in the environment of Elodea nuttallii (about 60% coverage). [ABSTRACT FROM AUTHOR]