Relationship between stocking rate and production of stocker hybrid tilapia and water quality in a mixtotrophic biofloc system

Intensified production of stocker-size tilapia can be accomplished using the biofloc technology production system. Stocker-size tilapia (ca. 10–200 g/fish) are raised for subsequent stocking for grow-out to market size. The relationship between stocking rate and the production of stocker-size hybrid tilapia (Oreochromis aureus × O. niloticus) was evaluated in two studies in outdoor mixotrophic biofloc tanks. Hybrid tilapia were stocked in 18.6-m² (15.7-m³) tanks at 50–150 fish/m² (59–178 fish/m³) in 25 fish/m² (30 fish/m³) increments in Study 1 and grown for 141–143 days. Stocking rates evaluated in 4.7-m² (3.6-m³) tanks during Study 2 over 78–79 days ranged from 100 to 300 fish/m² (132–396 fish/m³) in 25 fish/m² (33 fish/m³) increments. Linear regression models best described growth to stocker size in both studies. Fish yield increased linearly with stocking rate and ranged from 20.1 to 38.3 kg/m³. Individual weight at harvest was inversely related to stocking rate and ranged from 389.8 to 163.4 g/fish and 155.2 to 81.4 g/fish in Studies 1 and 2, respectively. Partial budget analyses suggested positive net changes in profit with incremental increases in stocking rate for producing a 75-g stocker. Water quality concentrations were impacted directly by daily feed ration and total feed fed, which increased linearly with stocking rate. In Study 2, whole-body dry matter, protein, protein retention, and lipid were unaffected by stocking rate, whereas whole-body ash increased with stocking rate. Whole-body energy retention significantly decreased with stocking rate. The outdoor mixotrophic biofloc production system is well suited for intensive production of hybrid tilapia stockers. However, additional replicated research and economic analysis are needed to evaluate stocking rate and culture duration to produce specific-sized stocker hybrid tilapia.