Aquacultural research has been conducted collaboratively in Honduras since 1983 by the International Center of Aquaculture and Aquatic Environments, Auburn University and the Direcion General de Pesca y Acuicultura, Secretaria de Recursos Naturales. This research was carried out at the El Carao National Fish Culture Research Center, Comayagua, Honduras, under the auspices of the USAID-financed Pond Dynamics/Aquaculture Collaborative Research Support Program (PD/A CRSP). The goal of PD/A CRSP is to increase tilapia yields by optimizing resource use in systems based predominantly on natural pond productivity.
Ponds were stocked with male Nile tilapia (Oreochromis niloticus). Pond nutrient inputs were organic and chemical fertilizers, and supplemental feed either alone or in some combination. Fish stocking rate was 10,000/ha during the initial five years of work. During this same period, experiments were repeated during the rainy and dry seasons on the assumption that seasonal differences would significantly affect pond productivity. However, temperature proved to be the factor that affected fish growth most, and the cooler period of the year overlapped the rainy and dry seasons. Thereafter, a warm and cool experimental season was used rather that a rainy and dry season. Differences in fish yield between warm and cool seasons can exceed 25 percent.
Stocking more than 10,000 fish/ha in organically-fertilized ponds resulted in smaller fish and no greater fish yields. Increasing stocking rate to 20,000/ha resulted in greater yield when organic fertilizer (chicken litter) was supplemented with nitrogen as urea. In research on the combination of organic fertilization and supplemental feeds, feed use was more efficient when combined in low amounts (1.5% biomas/d) with fertilizer, or when used beginning the third or fourth month of grow-out. Higher economic gains with feed over sole use of chicken litter were never realized at greater than returns from organic fertilizer plus nitrogen as urea. Tilapia yields of 3,500kg/ha in 150 days were obtained in fertilized ponds without feeds. Yields increased to 5,300kg/ha in 150 days when supplemental feeds were used, but high feed cost reduced net returns to less than those for fertilizers alone.
Assuming a market value independent of fish size, manure plus urea was the most profitable management system. Sixteen pond management strategies resulted in positive economic returns. All treatments with positive economic returns used stocking rates of at least 20,000 tilapia/ha. Production of large tilapia (>400g) necessitates the use of formulated feeds, but a higher market value for large tilapia is required in order for profitability of this management system to exceed that of systems based on organic fertilization plus urea. Large tilapia generally are produced for export markets, and require more intensive production practices. Tilapia harvested from semi-intensively managed ponds can supply domestic markets in Central America. Combined use of organic and chemical fertilizers as nutrients inputs for tilapia ponds requires less capital expenditure than commercial feeds, and therefore are appropriate for small- to medium-scale commercial producers who supply domestic markets.