Tolerance and Mortality of Gambusia affinis to Acute Ammonia and Nitrite Exposure at Various Salinities

Abstract

Tolerance and mortality of mosquito fish, Gambusia affinis to acute ammonia and nitrite exposure at various salinities were studied in fibreglass tanks (500L) for a period of 4 months at KAU Fish Farm, Faculty of Marine Sciences, Jeddah. Salinity tolerance was tested in 0 (Control) 10, 20, 30 and 40 ppt. After tolerance study, 60 fish from each salinity was taken for ammonia and nitrite exposure study. Ammonia toxicity was tested in 0, 0.5, 1, 2, 3 and 4ppm; while nitrite was tested at 8, 10, 12, 14 and 16 ppm. Survival decreased when salinity increased from 0 to 40 ppt and a significant relationship (R2=0.959) was found between increase in salinity and survival. Mortality rate was found to be increased when ammonia and salinity level increased and the highest mortality was observed in the highest dosage of ammonia (4ppm) and salinity (40ppt). Similarly, increased mortality was observed in higher levels of nitrite and salinity. Results show that Gambusia affinis can tolerate salinity up to 40 ppt, ammonia at 1ppm and nitrite toxicity at <8ppm.