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

Authors: Green, Bartholomew - Bart; Rawles, Steven - Steve; Ray, Candis; McEntire, Matthew - Matt

Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2024
Publication Date: 6/25/2024
Citation: Green, B.W., Rawles, S.D., Ray, C.L., McEntire, M.E. 2024. Relationship between stocking rate and production of stocker hybrid tilapia and water quality in a mixtotrophic biofloc system. Journal of the World Aquaculture Society. Article e13087. https://doi.org/10.1111/jwas.13087.
DOI: https://doi.org/10.1111/jwas.13087

Interpretive Summary: The biofloc technology production system is used increasingly for intensive production of tilapia. Stocker-size tilapia (about 1/4 - 1/2 lb per fish) are raised for subsequent stocking for grow-out to market size. The effect of initial stocking rate on production of stocker-size hybrid tilapia (blue tilapia x Nile tilapia) was evaluated in two studies in outdoor biofloc tanks. Hybrid tilapia were stocked in tanks (550 cubic feet volume) at 1.7-7.5 fish per cubic foot in 0.9 fish per cubic foot increments in Study 1 and grown for 141-143 days. Stocking rates evaluated in tanks (127 cubic feet volume) during Study 2 over 78-79 days ranged from 3.7-11.2 fish per cubic foot in 0.9 fish per cubic foot increments. Fish yield increased linearly with stocking rate and ranged from 1.25- 2.39 lb per cubic foot. Individual weight at harvested was inversely related to stocking rate and ranged from 0.86 to 0.36 lb per fish and 0.34 to 0.18 lb per fish in Studies 1 and 2, respectively. Water quality variable concentrations were impacted directly by daily feed ration and total feed fed, which increased linearly with stocking rate. Production of 1/4 -1/2-lb stocker hybrid tilapia was achieved in 79 days or fewer at stocking rates of 1.7-8.3 fish per cubic foot. These data will aid in planning management strategies for efficient production of stocker size hybrid tilapia.

Technical Abstract: 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 x 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 100-300 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 20.1-38.3 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.