Survival, growth performance, length–weight relationship and biochemical composition of cultured rainbow crab (Cardisoma armatum) fed plant and animal protein diets

Preliminary research on the domestication of the mangrove fisheries resources especially those with high aquaculture potential, is mandatory towards achieving sustainable, nutrient-rich food sources that can reduce protein and micronutrient deficiencies in coastal and food-insecure regions. This study evaluates the domestication chances, survival, growth performance, length-weight relationship, and chemical composition of African rainbow crabs (Cardisoma armatum) fed compounded diets from plant and animal sources. A total of ninety (90) C. armatum individuals (mixed sex), with an average body weight of 23.97 g, carapace length of 3.56 cm and carapace width of 4.37 cm were used in this study. They were allocated to three treatment groups [complete source diet (control), plant source diet, and animal source diet], each with three-unit replicates, and each experimental unit was stocked with ten individuals. The crabs were cultured for 16 weeks and fed 3% of their body weight. After the completion of the feeding trial, the crab tissues were manually collected from their bodies, processed, and analyzed for their biochemical composition. The final body weights were 112.45 ± 7.14 g for C. armatum fed a complete diet, 99.98 ± 4.34 g for a plant source diet, and 120.85 ± 2.69 g for an animal source diet. The crabs fed the animal source diet had the overall best growth rate, while the highest survival rates (66.67%) were recorded for the crabs fed the complete source diet. The results obtained for the length–weight relationship of the crab samples showed a negative allometric growth pattern (b < 3). The condition factor (k) values for females, males, and pooled sexes were greater than 1. Molting process occurred but no egg development was observed during the experiment. The chemical contents of the C. armatum samples showed that the choice of ingredients utilized in feed formulation influenced the crude protein, total ash, calcium, and sodium contents of the experimental crabs.