Evaluation of growth, production and cold tolerance of four varieties of tilapia

Abstract

As global tilapia production grows, it is important to characterize varieties available for production and generate data on environmental tolerances. This study generated data on tolerances, adaptabilities and production characteristics of four tilapia varieties. Goals of this study were to: (1) compare growth of four tilapia varieties in two types of recirculating systems, (2) evaluate juvenile growth of seven tilapia varieties in fresh and brackishwater mesocosms, and (3) estimate cold tolerance of juveniles of four tilapia varieties in fresh and brackishwater. Nile tilapia (Oreochromis niloticus), blue tilapia (Oreochromis aureus), Mississippi commercial strain tilapia (MCS), and Florida red tilapia (FRT) were grown in a clear-water recirculating system for eight months. Blue tilapia yields were greater (P¡Ü 0.05) than those of Nile tilapia and FRT. Yields of Nile tilapia, MCS, and FRT were not significantly different. Seven tilapia varieties: Nile, blue, FRT, MCS, blue x FRT, Mozambique x Nile, and Nile x blue were grown in fresh and brackishwater mesocosms. Nile tilapia was stocked in three freshwater pools. Every other variety was stocked into six pools, in three of which salinity was increased to 23 ppt over 14 days. In freshwater, yield of MCS was greater (P¡Ü 0.05) than that of all other varieties. Four tilapia varieties: Nile, blue, FRT and MCS were subjected to three temperature reduction regimes: rapid (-0.5 C/ 5 h), moderate (-1 C/ 24 h) and gradual (-1 C/ 48 h) and to the moderate reduction regime at three salinities (0, 5 and 10 ppt). No significant differences were observed in cold tolerance among varieties within temperature reduction regimes. Salt did not improve the cold tolerance of blue, Nile and MCS but slightly improved that of FRT. Performance of four tilapia varieties: Nile, blue, MCS and FRT in four culture systems was ranked to develop index values. Cold tolerance of four tilapia varieties was described from an environmental standpoint, with no significant differences found between varieties. The influence of the temperature reduction regimes on cold tolerance was significant.