Epidemiological Studies on Infectious Diseases of Marine Cage-cultured Fish in Penghu Sea

• Main Authors: Kuo Ren-Jeng, 郭仁政
• Other Authors: Tsai Shinn-Shyong
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/50075559713972647548

碩士 === 國立屏東科技大學 === 獸醫學系 === 91 === The Marine cage-culture of Taiwan has began from Penghu county and the Penghu sea. Cage-culture farming of fishes is the major direction of fishery in the future. But the fish disease and epidemiology of this type of farming are urgently to investigate for the monitoring and preventing the problem of the disease. This study investigated and analysed the aetiology and the pathology of the infectious disease of this type of farm fish in the Penghu sea area. In the meantime, it also studied the connection between the environment and the disease occurring. Results of the investigation from 1997 till 2002, have shown that the most significant pathogenic disease of marine cage-culture fish was found to be bacteria disease with the frequency of 63.3%(195/308). Then it followed the parasitic disease with frequence of 28.5%(88/308), more over, the viral disease which represented 7.5% (23/308), among all of the disease cases there were only 2 cases found to be induces by fungi. It was accidental infection. One hundred seventy four bacterial strains were Gram’s negative from 195 isolated strains (89.2%), including pathogenic Vibrio spp. 33.3%(65/195), Photobacterium damselae subsp. piscicida, 26.2%(51/195), and Aeromonas spp. were 11 strains(5.6%). While 21 bacterial strains isolated were Gram’s positive from 195 isolated strains(10.8%). Streptococcus iniae in this part was 61.9%(13/21), It showed that Strep. iniae is the major pathogen of Gram’s positive group of bacteria in the Penghu sea area. The less important disease was parasitic infestation. In these cases the infection of protozoa had 70.5%(62/88), Trichodina sp. was the most serious one 45.5%(40/88). As to viral diseases, the Iridovirus disease and Lymphocystis were found on red sea bream and grouper, and were 34.8%(8/23) and 65.3%(15/23) respectively. Because cobia is the major species of this particular type of farm culture, it was found that pseudotuberculosis and lymphocystis were most frequent diseases to occur. Thus those rate are much higher. Fish diseases always happen in the first year of cultivation, especially the first early 6 months, but when they survived over the winter it would no problem afterward. Therefore it is important that the pathogens in the sea, the ambient temperature and the host healthy status are interacting each other, to show up the epidemic. Farther more, many pathogens are actually carried from the hatchery, and during the transporting, the fish are injury and stress at this early stage of cultivation could come across the serious loss. It is especially true on Trichodina infestation with a secondary bacterial infection. For this reason, the young fish should get primary quarantine and disinfection before transfer to the cage. The hatchery and subsequent grower should eliminant the abnormality and the pathogen is detected and properly treated as soon as possible, In this way, it can control the disease of fry, including iridovirus infection, and simultaneously is should reduce the stress factor, with the effective vaccine, to control fish diseases of the marine cage-culture.