In Kundapur, Udupi district, an outbreak of Red Sea Bream Iridovirous (RSIV) disease in cage farming leading to the death of fish has again been reported.
It was previously reported during the 2018 and 2019 winter seasons.
Scientists from the Department of Aquatic Animal Health Management, Fisheries College, Mangaluru, who visited the Thallur estuary near Kundapur on Sunday, reported that there is a risk of contamination spreading to ecotone and coastal waters, affecting not only nurtured fishes, but also other fishes.
Since there is no cure for RSIV, diseased and dead fish should be cleared and buried or burned in a safe place immediately. As the water is free flowing, the spread of the virus in the waters is hard to control, the college scientist team said.
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The College Dean, A. Senthil Vel, in a press release on Tuesday, said that a team comprising Assistant Professor Girisha S.K. Nithin and Research Staff, Kushala K. B. and Soundarya visited the site On Sunday, and witnessed large-scale fish deaths in one unique cage of sea bass and contaminated fish in the other cage. They conducted meetings with officials from the Fisheries Department and collected samples of water in and around the floating fish cages.
For microbial and viral research, dead, moribund and seemingly stable fish samples were collected and brought to the college laboratory. Based on the study, approximately 2,000 fish of 40-60 grammes each in two cages were found to have been infected or dead due to RSIV, Prof. Vel said, adding that the internal organ analysis of these dead fish displayed enlarged spleen and dull skin coloration.
The release claimed that the State Government should make it compulsory for fish seeds procured by farmers to be sold only by accredited vendors of fish seeds.
“The probable spread of the viral disease may be due to high stocking density in these cage culture farms. It is important to carry out proper housekeeping, hygiene, disease prevention measures and monitoring,” Prof. Vel informed.
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The release said that apart from high stocking density, cages have very little water depth during low tide, thus increasing fish stress during low tide. During low tide, the higher fish population density and low water levels lead to stress, thus becoming a fertile ground for such virus stimulation.
“Highly carnivorous, the cultured sea bass are fed with trash fish. If due care is not taken and contaminated feed is given, the risk of RSIV infection increases. It is recommended that such fish may be provided with authenticated commercial feed,” he mentioned.
The release said that it was mentioned during discussions with fish farmers that water has a high amount of pollution level, mainly from sewage water.