THE EFFECT OF SALINITY ON GROWTH AND SURVIVAL OF PENAEUS-VANNAMEI, WITH OBSERVATIONS ON THE INTERACTION OF IHHN VIRUS AND SALINITY

Penaeus vannamei juveniles (initial mean weight = 1.6 g) were cultured at salinities of 5, 15, 25, 35, and 49 ppt for 35 days. Highest mean final weights and greater than 2 g/week growth were obtained in the lo west salinities tested, 5 and 15 ppt. Mean final weights at 5 and 15 p pt were not significantly different, but were significantly greater th an at the higher salinities tested. Mean final weights at 25 and 35 pp t were not significantly different, but were significantly greater tha n at 49 ppt. Mean final weights by treatment were: 12.4 g (5 ppt), 12. 2 g (15 ppt), 10.8 g (25 ppt), 11.1 g (35 ppt), and 9.8 g (49 ppt). Su rvival was not significantly different among salinity treatments. A se cond population of juveniles (initial mean weight = 2.2 g), infected w ith IHHN virus (infectious hypodermal and hematopoietic necrosis virus ), was compared concurrently at 25 and 49 ppt. The growth pattern was similar, with significantly higher mean final weights at 25 ppt than a t 49 ppt. Additionally, a significant interaction between population a nd salinity level (two-way ANOVA, P = 0.035) indicated that the IHHN-p ositive population had relatively lower growth at the high salinity le vel. Mean final weights in the second population were 10.3 g (25 ppt) and 8.5 g (49 ppt). As in the population not infected with IHHN, survi val was not significantly different among treatments.