Tilapia could be stocked in very small ponds at high densities and still thrive. Backyard aquaculture systems (BAS) are gaining importance as a source of food and economic input for rural families in Mexico. Here is presented a bioeconomic model of BAS developed for tilapia production at a low scale in rural areas of Mexico.
Backyard systems are considered agroecosystems in which domestic groups produce various species of animals and plants in a homemade way for food self-sufficiency and economic savings. These promote social and family coexistence and integration to improve food security and contribute to poverty reduction.
Labor and land cost savings are the key elements for backyard systems’ economic viability. Aquaculture is a productive activity, with a growth rate of 46.8% in 10 years (2010-2019).
From all aquaculture species, the group of tilapia ranked second among the finfish species, highlighting the production of Nile tilapia (Oreochromis niloticus), which, in 2018, was the third most produced species in the world (FAO, 2020).
“Tilapia tolerates very poor water quality conditions and will survive oxygen depletions that would kill most other fish, so they could be stocked in very small ponds at high densities and still thrive. Tilapia will produce acceptable weight gains on various inexpensive, low-quality feeds, reducing production costs.”
In 2019, the demand for tilapia in Mexico was nearly 300,000 t, of which 168,000 t were produced locally, and the rest (127,981 t) were imported from Asia. Apart from being Mexico the second importer of tilapia in the world after the USA, local demand is growing at an annual rate of 9%; therefore, aquaculture production needs to be increased.
The profitability of backyard aquaculture in different scenarios has yet to be determined. Bioeconomic models are made up of a biological, a production, and an economic sub model, which evaluate the behavior of a system in which the development of a living organism is integrated with certain exogenous and endogenous variables typical of the production system and the market.
In this work, a bioeconomic model composed of a biological, production, and economic sub-model was developed to evaluate the low-cost backyard aquaculture system (BAS) appropriate for rural communities in Mexico, at different sale prices, at certain water temperature conditions, and at self-consumption levels.
Materials and Methods
The Backyard Aquaculture System (BAS) was designed as a closed-flow system that was easy to operate, to which partial water exchanges were done depending on the ammonium concentrations. It consists of a 2,800 L plastic water tank (1.86 m diameter × 1.18 m height) to which venture type submersible pumps of 0.046 hp are fitted to recirculate the water at 1,400 L h-1 and oxygenate the water at a rate of 1.2-2.4 kg O2 kW h-1 (Figure 1).
For the model, the biological and culture parameters were those that, in practice, have been demonstrated to be appropriate for tilapia O. niloticus cultivation.
After stocking, the daily activities include temperature checking with a digital thermometer, ammonium concentration determinations using an Ammonia Test Kit (Salicylate), and chlorine (if municipal water is employed) with a free chlorine test kit.
Production will depend on the fish’s final weight, which the model will calculate. The sale price was USD 3.62 kg-1 = USD 1.64 lb-1 at an exchange rate of 1 USD = 20 MXN.
The bioeconomic model was composed of three sub-models (i.e. biological, production, and economic) (Figure 2).
The biological sub-model comprised the dependent and independent variables directly influencing growth: biomass, oxygen requirements, temperature, and expected mortality.
Results
The temperature growth coefficient (TGC) was 0.02400, allowed us to build the growth rate curve of Figure 3, and find the final weight of 614 g in the 25 week-cycle. Considering this individual weight and 10% mortality, 186 kg yr-1 of fresh tilapia will be harvested.
Five kilograms of initiation, 89 kg of intermediate, and 129 kg of finalization feeds will be employed, giving 223 kg of balanced feed per year, resulting in a 1:1.2 feed conversion factor. Considering the oxygen transfer capacity of 1.2 kg O2 kW h-1 of the venturi pump, two pumps will be required to meet the O2 demand until the end of the culture.
Considering the final weight of the fish, the quantity of feed required, and the number of pumps, the total investment required to build and operate the BAS for one year will be USD 1,200 (Table 1), including USD 775 of investment (equipment) and USD 425 of production costs.
The equipment list includes scales for biometrics, nets for handling the fish, cleaning tools, a digital thermometer, and a spare venture pump. The operation costs include fry, feed, cleaning reagents, electricity, ammonium and chlorine kits, water, and maintenance.
Total costs per year will be USD 425.26, giving a cost per kg of USD 2.29, considering an annual production of 186 kg. Selling the fish at USD 3.62 kg-1, the gross income (GI) will vary from USD 673 to 503 at 0% and 25% self-consumption, resulting in positive net profit (NP) and net profit margin (NPM), which indicate breakeven values at 25% self-consumption since above this percentage, NP becomes negative.
However, profitability indicators at 25% self-consumption are negative because of the deduction of the discount rate of 8.3% per year. With these indicators, the payback period (PP) will be three and four years for 0% and 10% self-consumption and longer than five years for 25% self-consumption.
“Different scenarios of profitability indicators: cost benefit, net present value (NPV) and internal rate of return (IRR) at different self-consumption percentages and different prices and temperatures were calculated. It is evident that indicators are higher at 0% self-consumption, at the highest temperature tested (32°C) and at the higher sale price.”
The annual production of tilapia in terms of the number of fish and weight harvested available for self-consumption and sales at different self-consumption percentages demonstrated that at 0% self-consumption, 303 fish and 186 kg will be available for sale.
However, if 10% of production is destined for self-consumption, 31 fish of 614 g and 19 kg will be available to feed the family and will generate revenues of USD 605 by selling 272 fish and 167 kg. At 25% self-consumption, 75 fish and 46 kg will be available for feeding the family, equivalent to 1.4 fish and 0.88 kg per week.
Financial self-sustainability will be reached at this level of self-consumption since the revenues will be enough to cover the production costs.
Discussion
In this work, evaluating the BAS with the bioeconomic model resulted in a viable, self-sustainable alternative for tilapia production at a low scale in rural areas of Mexico and other Latin American countries. With a low investment of USD 1,200, the BAS could produce high quality food, contributing to food security and poverty reduction, providing extra income for the family.
Regardless of the low-scale production system, BAS is profitable because labor and land have no cost. At 10% self-consumption, a family of five members could consume 3.8 kg of fish yr-1, a figure that is above the average per capita apparent tilapia consumption in Mexico (3.08 kg ind-1) and in the world (0.9 kg ind-1).
At this percentage, there will be a NP of USD 117, which could contribute to the family’s economy. The harvest of fish for self-consumption or sales could be anticipated several weeks before reaching week 25 since not all fish attain the same size simultaneously.
“So, partial harvests of the larger fish could be done, bringing the advantage of gradually reducing the culture density and availability of food and revenues for the family.”
There are several requirements for the successful application of the BAS. This system is suitable for warm areas of Mexico and Latin America, where average water temperatures above 28°C are registered. Water and electricity supply are also indispensable requirements for the operation of the BAS.
Among the project’s risks is the occurrence of diseases caused by bacteria, fungi, and ectoparasites. However, as pointed out before, tilapia is a highly resistant species to diseases, and its susceptibility diminishes with age and size.
The results of the project could be enhanced with several actions. The same family could expand its production capacity by reinvesting their profits to increase the number of tanks. They may also increase revenues by selling the fish live since this finished product presentation is highly valued and getting more popular.
The major challenge to overcome is adopting this new activity into the family’s daily routine. The routine includes feeding the fish according to the feeding tables, which indicate the quantity and type of feed to be employed according to the fish size, which implies weighing the fish and selecting the correct feed for the developmental stage.
It also includes monitoring water temperature, ammonia, and chlorine (if municipal water is employed) and making water changes if needed. The correct administration of funds will be important to pay for supplies and save funds for the next cycle.
“Qualified extensionists could tackle these cultural aspects with appropriate training and supervision. Although the culture parameters of this work were carefully selected, it would be convenient to corroborate results in an experiment in different locations with different temperature regimes.”
With this experiment, it would be possible to make the necessary adjustments to the model, if needed, for later use as a tool for evaluating existing projects and planning future projects.
In this work, the model selected for growth prediction considered the stages of development and the effect of temperature using the thermal growth coefficient since it was imperative to quantify with high precision the feeding rate and food requirement.
In conclusion, the evaluated BAS proved to be a viable, self-sustainable alternative for tilapia production at a low scale in rural areas of Mexico and other Latin American countries.
A specially designed government program is required to promote and finance this activity. Mexico has to try to increase its tilapia production since it has a deficit of nearly 128,000 t yr-1 imported from Asia, the second largest international market for tilapia products.
The BAS system could contribute to diminishing the deficit if families in rural areas of Mexico massively adopt it.
This is a summarized version developed by the editorial team of Aquaculture Magazine based on the review article titled “BIOECONOMIC MODEL FOR THE EVALUATION OF A BACKYARD AQUACULTURE SYSTEM FOR TILAPIA (OREOCHROMIS NILOTICUS) developed by: JUAN CARLOS R. DORANTES-DE-LA-O & ALFONSO N. MAEDA-MARTÍNEZ – Unidad Nayarit del Centro de Investigaciones Biológicas del Noroeste S.C., Tepic, Nayarit, México.
The original article, including tables and figures, was published on DECEMBER, 2022 through LATIN AMERICAN JOURNAL OF AQUATIC RESEARCH.
The full version can be accessed online through this link: DOI: 10.3856/vol51-issue2-fulltext-2999
