Influence Of Brackish Water On Survival And Growth Of The Juvenile White Grouper, Epinephelus Aeveus

Abstract

The natural habitat of the white grouper, Epinephelus aeneus, is the Mediterranean Sea, which has a salinity of approximately 35 ppt. As fish species vary in their tolerance of environmental conditions, potential production in specific conditions must be determined empirically. The growth, survival and cortisol level of 1.7 g grouper juveniles grown in diluted sea water (4 ppt) or brackish water (4 ppt) from the Tsofar well in the Arava (southeastern Negev, Israel) was com- pared to the growth of similar fish in sea water (43 ppt). Survival in all treatments was 100%. During the first ten days, the fish grown in brackish water grew significantly less (p<0.01) than the fish grown in full-strength or diluted sea water. There were no significant differences between the treatments during the second growth period or in the final weight (approximately 9 g). Total cortisol concentrations ranged 2.7-4.5 ng/l and did not significantly differ between treatments. Results indicate that the white grouper can flourish in water with salinity as low as 4 ppt and that there are no detrimental chemical factors in the brackish water from the Tsofar well.