Optimization of stocking and harvesting strategies in intensive culture of tilapia (Oreochromis niloticus), considering minimum marketable sizes

The stocking and harvesting strategies used in aquaculture have a strong influence on the economic yields, and producers of aquatic species need alternatives that improve culture conditions and production economy. In this study, we used tilapia growth data from construct bioeconomic models to determine the best stocking and harvesting strategies under homogeneous (HM) and heterogeneous (HT) stocking sizes. We considered 180, 195, 210, and 225 days to harvest. Minimum marketable sizes (MMS) (minimum harvestable fish sizes) were defined according to the market as 350, 400, 450, and 500 g. The bioeconomic analysis considered a fixed price and a price that was variable depending on the size of the fish. With an average growth model and fixed price of USD$ 2.24 kg −1 , independent of MMS, the economic results were negative under both HM and HT stocking and for all harvest times. With size-dependent variable pricing, the highest net benefit was generated by the 225-day, 500 g harvesting strategy, with USD$ 5061.91 per tank under HM and USD$ 5220.53 per tank under HT. Using quantile regressions and fixed pricing, the 225-day, 350 g strategy had the highest yield under HM and HT, with USD$ 4323.51 and USD$ 4190.90 per tank, while with variable pricing, the 225-day, 450 g strategy had higher yield in HM and HT, with USD$ 8634.03 per tank and USD$ 8983.26 per tank. Thus, growth modeling using quantile regression to approximate the population distribution suggested that HT stocking and size-dependent variable pricing generate higher yield for tilapia producers.