Water quality in floating net cages pond of humpback grouper (Cromileptes altivelis) infected by viral nervous necrosis

Abstract

Humpback grouper (Cromileptes altivelis) is widely cultured in Indonesia due to its various advantages. Yet, the issue with humpback grouper pisciculture is the fact that it is prone to diseases, including bacteria, fungi, parasites, and viruses. The several disease-causing agents, viruses are quite dangerous agents. One of the viruses that can cause the failure of C. altivelis pond is Viral Nervous Necrosis (VNN), which causes stress due to poor water quality. The purpose of this study was to determine the condition of water quality in grouper floating net cages infected by VNN. The research method used in this research was the descriptive method with surveillance survey techniques, including measurement and analysis of water quality. Water quality observed include temperature, pH, Dissolved of Oxygen (DO), salinity, nitrate, and phosphate. Water quality sampling was carried out three times. Based on observations of the clinical symptoms of groupers that were indicated to have been infected by VNN, they showed physical signs of blackened skin and protruding eyes as well as swirling movements. The water quality of floating net cages was 26.7°C, 7.49, 8.53 mg L-1, 32, 0.101 mg L-1, and 0.002 mg L-1, for temperature, pH, DO, salinity, nitrate level, and phosphate level, respectively. Based on the results of the study, the quality of water found in grouper aquaculture was still classified as normal. VNN infection in groupers was possible through a vertical pathway derived from the broodstock.