Effect of size heterogeneity of Nile tilapia (Oreochromis niloticus) on the optimal harvest time: a bioeconomics approach

Abstract

A critical problem in the production of Nile tilapia Oreochromis niloticus in intensive and hyper-intensive systems is the heterogeneity of body sizes as it influences the final production and economic yield. The objective of this study was to calculate the bioeconomic effect of size heterogeneity on the production of Nile tilapia at a commercial level and to determine the optimum harvest time (OHT) considering four minimum marketable sizes target (Mms = 350, 400, 450, 500 g). Two seeding strategies were evaluated: homogeneous seeding (HM) with a 96.55 ± 24.51 g initial body weight and heterogeneous seeding (HT) with a 100.17 ± 5.91 g initial weight. Fish from both treatments were stocked at 40 fish m-3 in triplicate using a randomized design. The calculated quasi-profits of variable costs showed an inversely proportional relationship with the minimum market size in both groups. The smaller size dispersion in HM generated higher profits than HT. The OHT for Mms [350, 500 g] of HM population was 180 days, with a mode of 641 g. The OHT was also 180 days for the HT population but only for the Mms [350, 400 g] and a mode of 578 g. In terms of quasi-profits, the HM produced 19.93% more quasi-profit than the HT in the market size of 350 g at 180 days (HM = 0.50 US$ kg-1; HT = 0.44 US$ kg-1). The simple bioeconomic model presented here can help producers manage a series of economic decisions associated with OHT, when targeting different market segments requiring different Mms.

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

“…The OHT for the HT system was 196-229 days for the Mms of 350, 400, and 500 g. This time was shorter in the HM strategy, where the OHT was 181-221 days for Mms 350, 400, and 450 g. The Mms = 500 g presented a negative net profit of USD 235.96 in the HT system, while in the HM, the net profit was USD 615.40. The economic results are consistent with the conclusions of Pérez et al (2012) and Borrego-Kim et al (2020), in which they indicated that heterogeneity harms the optimization of biomass and yield as a function of time.…”

“…In previous works, we calculated the bioeconomic effect of size heterogeneity on commercial production of Nile tilapia. We demonstrated that the quasi-benefit of variable costs had an inversely proportional relationship with the minimum market size (Borrego-Kim et al, 2020). In this study, we use the results obtained previously to develop a bioeconomic model that includes the dispersion of size and Mms in the production of Nile tilapia and thus provide data on net profit.…”

“…The data used to perform the bioeconomic modeling comes from an experimental study conducted in a commercial tilapia farm (Yaxchilam Farm, Yucatan, Mexico) from February 2015 to January 2016 for 330 days (Borrego-Kim et al, 2020). The organisms were obtained from a batch of 100,000 sex-reversed Nile tilapia (Oreochromis niloticus) fingerlings (Spring Genetics).…”

“…The mortality rate at the final of the experiment was 3.89 and 2.33% for HM and HT, respectively. For more details, see Borrego-Kim et al (2020).…”

“…Aquaculture is an essential agricultural practice for food security worldwide (Klinger & Naylor, 2012;FAO, 2016;Føre et al, 2018) and Nile tilapia (Oreochromis niloticus) is one of the most popular species (Cai et al, 2018). Size dispersion occurs naturally in the population of tilapia (Barki et al, 2000;Borrego-Kim et al, 2020), and directly affects the profitability (Arnason et al, 1992), since there is a minimum marketable size (Mms) with commercial value. The effect of size dispersion is a recurring phenomenon beyond the inherent stochastic; such as stocking density, feeding conditions, temperature, and ration size (Barbosa et al, 2006;Peacor et al, 2007;Santos et al, 2008;Gullian et al, 2012;Gullian-Klanian & Arámburu-Adame, 2013;Domínguez-May et al, 2020).…”