Authors

Charry Neleene L. Paracueles

Author

School of Marine Fisheries and Technology, Mindanao State University at Naawan, 9023 Naawan, Misamis Oriental

*Corresponding author: [email protected]

ABSTRACT

Exposure of fish to ammonia has an acute toxic effect and certain high concentrations can cause massive mortalities in the cultured animals. This study was conducted in order to determine the 24 hour lethal concentration (LC50) of ammonia on Oreochromis niloticus fingerlings under local ambient condition. A total of 120 fingerlings with an average weight of 33.2 ± 0.23 g and an average length of 11-29 mm were used in the experiment. The test animals were distributed to 3L capacity plastic jars filled with 1L distilled water using a completely randomized design (CRD). The mean LC50 ammonia level is 4.10 ppm, a lethal concentration at which 50% of the fingerlings died. The computed mean LC25 is 2.025 ppm and mean LC75 is 8.31 ppm. The experiment showed that ammonia is very toxic to the fish with 100% mortality occurring after 1 hour and 2 hours of exposure to 20ppm and 15ppm, respectively. An average mortality of 83.3% occurred in 10ppm concentration after 4 hours of exposure. Behavioral responses to the intoxication include rapid swimming, rapid movements of the fins and operculum, efforts to gasp air from the surface of the water, and less mobility. External changes are increased secretion of mucous, darkening of the skin, and discoloration of the eyes. Results of this study have important implications on maintenance of water quality in aquaculture systems.