Betanodavirus infection in marine fish aquaculture in Malaysia

Betanodavirus is known to cause mass mortality in many marine aquaculture fish species. In this study, we detected the virus in four different marine aquaculture fish species in Malaysia. These included humpback grouper (Cromileptisaltivelis), brown marbled grouper (Epinephelusfuscoguttatus), Asian seabass (Latescalcarifer) and golden pompano (Trachinoltusblochii). Out of 246 fish specimens analyzed using RT-PCR, 60.98% detected infected by the virus. Histological pathological analysis showed extensive cell vacuolationin the brain and retina tissues of severely infected specimens. However, some of the fish specimens detected positive using RT-PCR did not exhibit cell vacoulation which indicate the carrier state of those specimens. The RT-PCR amplification method developed in this study was shown useful as biosecurity tool in monitoringBetanodavirus infection in aquaculture. Although the origin of Betanodavirus in Malaysia is difficult to ascertained, evidence showed that some infections may have been contributed by the importation of fish fingerlings form neighboring countries. Currently, effective treatment of the viral disease is still impossible hence strict biosecurity measures need to be carried out in order to control the spread of the virus in fish stocks. These can include enforcement of biosecurity check and quarantine of every batch of imported fish, the use of virus-free broodstocks in hatchery, and proper disposal of infected fish stocks. In addition, good aquaculture practices must be carried in aquaculture farms or fish nursery all the time

Light intensity requirements for feeding behaviour by the brown-marbled grouper, epinephelus fuscoguttatus

In this study, we investigated the feeding behavior of the brown-marbled grouper, Epinephelus fuscoguttatus with light intensities ranging over eight orders of magnitude from 0–1000 lx to estimate the optimum light intensity for larval rearing. Artemia ingestion rates of E. fuscoguttatus of 36 days and 42 days old larvae were measured in feeding behavior experiments and they were significantly higher with light intensities ≥10 lx compared with feeding rates at ≤1 lx. E. fuscoguttatus larvae also exhibited Artemia ingestion rates in the dark or in dim lighting (0–1 lx) that were about 20% of the ingestion rates with ≥10 lx

Light intensity requirements for feeding behaviour by the brown-marbled grouper, Epinephelus fuscoguttatus (Keperluan Keamatan Cahaya untuk Perlakuan Pemakanan Ikan Kerapu Harimau, Epinephelus fuscoguttatus)

In this study, we investigated the feeding behavior of the brown-marbled grouper, Epinephelus fuscoguttatus with light intensities ranging over eight orders of magnitude from 0 – 1000 lx to estimate the optimum light intensity for larval rearing. Artemia ingestion rates of E. fuscoguttatus of 36 days and 42 days old larvae were measured in feeding behavior experiments and they were significantly higher with light intensities ≥10 lx compared with feeding rates at ≤ 1 lx. E. fuscoguttatus larvae also exhibited Artemia ingestion rates in the dark or in dim lighting (0 – 1 lx) that were about 20% of the ingestion rates with ≥ 10 lx