Evaluation of Yellow Mealworm (Tenebrio molitor) Larvae Meal as a Carbon Source in Biofloc System for Dwarf Crayfish (Cambarellus montezumae) Culture.

Abstract

The aim of this study was to evaluate the use of Tenebrio molitor larvae meal as a carbon source in a biofloc system (BFT) to optimize the culture of C. montezumae. A trial was conducted for 24 weeks, 500 T. molitor larvae were reared with wheat bran as substrate, and hydration once a week; at the end, 9000 T. molitor larvae were obtained, which were processed to make meal. C. montezumae was conditioned for 2 weeks in two 100 L polyethylene tanks in clear water and fed with Tropical shrimp sticks until the beginning of the experiment. A 12-week experiment was performed with three treatments and three replicates each: control (no biofloc), biofloc with molasses (BFT-M), and biofloc with T. molitor meal (BFT-T) as carbon source, at a 20:1 C/N ratio, adjusted every 15 days based on the feed ratio. The culture parameters of the water during the experimental period varied, but they always remained within the range required for the species. No significant differences were observed in weight gain (WG) among the three treatments (p  > 0.05), but the crayfish cultured in the treatments with biofloc obtained the greatest WG and the lowest feed conversion ratio (FCR). In the biofloc, nine phyla of zooplankton were identified, of which 16 genera were present in BFT-M and 13 in BFT-T. The chitinolytic bacteria showed a greater diversity and richness in BFT-T compared to the BFT-M and control. Pseudomonas luteola was the dominant species, and Rhizobium radiobacter the second one. The nutritional composition (lipids, carbohydrates, fiber, ash, and moisture) of T. molitor as well as biofloc from the BFT-M and BFT-T showed significant differences (p  < 0.05), but not in protein levels. This study demonstrated that T. molitor meal is a viable carbon source in C. montezumae biofloc culture, improving biofloc nutritional quality through increased chitinolytic bacterial diversity.