Tolerance, Survival Rate and Growth of Tilapia (Oreochromis Niloticus) Fingerlings at Different Salinity Levels.

Abstract

The shortage of fresh water in many countries, together with the competition requirement for agriculture and other urban activities has increased the pressure to develop agriculture in brackish water and sea water. Tilapia is excellent candidates for aquaculture in brackish water due to their ability to tolerate a wide range of water salinity. Salt tolerance depends on tilapia species, strains and size, adaptation time and method and environmental factors. To develop a simple and accurate index of the salinity resistance of tilapia, batches of 30 fingerlings (6 to 10 g) of Oreochromis niloticus reared in fresh water were subjected to gradual increase in salinity. Fish were acclimatized in graded series of salinities after every two days. The mortality, monitored on a daily basis, appeared after 2-5 days with no deaths in the rest of the 11 weeks depending on the increment of salinity. The higher the daily rate in salinity increase, the shorter the time lapse before total mortality occurred. Growth at 10ppt and above was significantly higher than that of 5ppt and there was a clear increase in growth with salinity.