Monitoring of pathogens on the cultured Korean rockfish Sebastes schlegeli in the marine cages farms of south sea area from 2006 to 2008

Abstract

Pathogens on the cultured 579 rockfish, Sebastes schlegeli in the marine cage farms from Geoje and Tongyeong of the Southern sea were investigated from 2006 to 2008. The pathogens were detected through- out the year at 46.0~90.0% for 3 years and the detection rate was low with an average 58.1% in May and high with an average 81.5% in October. Bacteria only, bacteria-parasite mix and virus only were found in October and November as well as parasite only, whereas infection of parasite only was dominant in May when the temperature increased and in August when the temperature peaked. Of rockfish, Microcotyle sp. and Caligus sp. were dominant for parasitic disease, and Vibrio sp. and Streptococcus sp. were dominant bacteria. For virus, RSIV and VNNV were detected as dominant organisms. While no virus was detected in 2006, VNNV, VHSV and RSIV were detected in 2007 due to 1.5�2.0℃ higher temperature than 2006 in the summer season. For total prevalence by rockfish sizes, the highest was found at 50.0�87.1% in 11�15 ㎝ sizes and 50% was found in 30 ㎝ size. Parasite showed a similar trend of 50.0�79.6% as the total prevalence. Prevalence for bacteria varied from 1.6% (for 10 ㎝ group) to 23.8% (for 26 ㎝ group) and higher virus prevalence of 21.5% was found from below 25 ㎝ group.