The Effect of High Temperature on the Growth Performance of Hybrid Tilapia Oreochromis niloticus X Oreochromis aureus Juveniles Reared in a Recycling System

Tilapia juveniles live in littoral regions of freshwater ecosystems which have temperatures that may reach critical values for growth, especially in face of the onslaught of climate change. This study analyzes the effect of temperature (25, 30, 35, 40°C) on the growth and survival of hybrid tilapia juveniles in a re-circulating system. Duplicate groups of 30 juveniles were stocked in 200 L tanks in a closed, re-circulating system. Automatic heaters were used to establish the water temperatures, commercial food was supplied at 5% of their weight as daily ration. Fish were weighed and measured at 15-day intervals for a period of 3 months. Water temperature and dissolved oxygen were monitored daily. Ammonia, nitrates and dissolved reactive phosphorus were monitored every third day. Fish responses were estimated through variations in length, weight and inter-circuli space of fish scales. Average initial and final weight and length, Specific growth rate (SGR), Fulton Index (FI), Length-weight relationship and survival were used to assess tilapia growth performance. Weight, length, SGR and FI were significantly affected (P < 0.05) by water temperature. Growth of the fish reared at 30oC was almost one third greater than that at 25°C and one sixth greater than that at 35°C. Except for fish reared at 40°C, the other treatments showed a positive allometric growth, with the better results recorded for the 30 and 35°C treatments. The fish reared at 40°C survived only two weeks while the survival rate of 98, 90 and 88.3% for 25, 30 and 35°C, respectively.