Bioeconomic modeling of optimal harvest time in Nile tilapia (Oreochromis niloticus) considering size heterogeneity and minimum marketable size

Abstract

Size dispersion in farmed fish has a substantial impact on production's bioeconomic performance, directly affecting net profits. This work's objective was to develop a bioeconomic model based on experimental data to identify the optimal harvest time (OHT) for Nile tilapia Oreochromis niloticus. The bioeconomic model considered four minimum marketable sizes (Mms = 350, 400, 450, and 500 g). Organisms were selected by size with different coefficients of variation (CV). Therefore, they were reared under two growth strategies: heterogeneous size (HT = 44-155 g; CV 25.5%) and homogeneous size (HM = 87-112 g; CV 5.9%). The HT system-generated tradable biomass of 99.30% in an OHT of 196 days with a net profit of USD 3,551.61 and a Mms of 350 g. However, the HM system achieved greater marketable biomass (99.53%) in less time (OHT = 181 days) with a net profit of USD 3,327.96 for the same Mms. The Mms of 500 g had the lowest net benefit in both systems. The HM strategy earned an additional 10.66% of incomes, indicating that the reduction in size dispersion positively impacted profits. The developed model provides a new perspective regarding the management of heterogeneity and size homogeneity in commercial production of Nile tilapia in intensive systems.

Modeling Nile Tilapia Heterogeneous Growth under Different Stocking Densities during Pre-Grow-Out Stage

“…In this case, stocking density affected tilapia growth in the pre-grow-out stage showing an inverse relationship, i.e., growth rates decreased as the initial density increased [101]. The determination of intrapopulation heterogeneity is important since it provides information closer to reality and helps decision-making in the different production stages [42][43][44], especially in vertically integrated farms where the objective of pre-grow-out stage is to optimize scarce resources and reduce production costs determining the optimal transfer time to the grow-out stage [102].…”

“…However, there is evidence that organisms on farms grow heterogeneously under different rearing conditions. Since slight changes in final weights could cause significant changes during economic valuation, some studies have evaluated heterogeneous growth (HtG) for determining productive performance and economic benefit [21,[39][40][41][42][43][44][45][46].…”

“…Tilapia growth has been previously modeled in the pregrow-out stage considering size homogeneity [2]. However, models with HtG are still scarce [31,43,44,57]. To date, to our knowledge, works regarding the HtG of Nile tilapia in pre-grow-out stage have not been found.…”