Disease monitoring of Alaska pollock (Gadus chalcogrammus) based on growth stages

명태 (Gadus chalcogrammus)의 성장 단계별 질병 모니터링

  • Kim, Kwang Il (Aquaculture Industry Research Division, East Sea Fisheries Research Institute, NIFS) ;
  • Byun, Soon-Gyu (Aquaculture Industry Research Division, East Sea Fisheries Research Institute, NIFS) ;
  • Kang, Hee Woong (Aquaculture Industry Research Division, East Sea Fisheries Research Institute, NIFS) ;
  • Nam, Myung-Mo (Aquaculture Industry Research Division, East Sea Fisheries Research Institute, NIFS) ;
  • Choi, Jin (Aquaculture Industry Research Division, East Sea Fisheries Research Institute, NIFS) ;
  • Yoo, Hae-Kyun (Aquaculture Industry Research Division, East Sea Fisheries Research Institute, NIFS) ;
  • Lee, Chu (Aquaculture Industry Research Division, East Sea Fisheries Research Institute, NIFS)
  • 김광일 (국립수산과학원 동해수산연구소) ;
  • 변순규 (국립수산과학원 동해수산연구소) ;
  • 강희웅 (국립수산과학원 동해수산연구소) ;
  • 남명모 (국립수산과학원 동해수산연구소) ;
  • 최 진 (국립수산과학원 동해수산연구소) ;
  • 유해균 (국립수산과학원 동해수산연구소) ;
  • 이주 (국립수산과학원 동해수산연구소)
  • Received : 2017.01.31
  • Accepted : 2017.03.16
  • Published : 2017.03.31

Abstract

The Alaska pollock (Gadus chalcogrammus) belongs to the family Gadidae; it is a cold water fish, and has been developed as a novel aquaculture species in Korea. In this study, we describe ongoing surveillance for aquatic animal pathogens based on growth stages. We investigated bacterial flora in rearing water, and monitored pathogens; we also analyzed histopathological traits of abnormal fish. In rearing water, the total bacterial counts were $2.1{\times}10^3cfu/mL$ and Vibrio spp. (52%) were predominant in the larvae stage. In the juvenile and adult stages, the total bacterial counts were $3.4{\times}10^3$ and $3.2{\times}10^2cfu/mL$, respectively (with Pseudomonas sp. as the predominant species; 90% and 52%). This result revealed that the bacterial flora in rearing water changed depending on the feeding types. No virulent-bacteria or problematic viruses (VHSV, viral hemorrhagic septicemia virus; NNV, nervous necrosis virus; MBV, marine birnavirus) were detected from outwardly healthy fish using either culture or PCR assay. Some juveniles (less than 5%) had gas bubbles on the gill lamellae, degeneration of the corneal epithelium, and choroid gland degeneration, suggesting that these symptoms were caused by external injury and secondary infection by opportunistic bacteria. Disease management is important to cope with disease emergence in the novel aquaculture species Alaska pollock.

본 연구에서는 명태 양식 기술 개발 과정 중 수산생물 병원체의 영향을 알아보고자 사육수 내 총 세균수 변화, 분포와 명태에 대한 영향을 분석하였으며, 성장 단계별 명태의 병원체(세균, 기생충 및 바이러스) 조사 및 비정상 개체 발생에 대한 원인 구명을 수행하였다. 자어 단계에서 사육수의 평균 세균수는 $2.11{\times}10^3cfu/mL$로 나타났으며, 비브리오균이 52%로 가장 높게 분포하였다. 치어 및 미성어 단계에서 사육수의 세균수는 $3.43{\times}10^3cfu/mL$(슈도모나스균 90% 분포) 그리고 성어 단계에서는 $3.2{\times}10^2cfu/mL$(슈도모나스 52%)로 나타났다. 명태 사육수 세균총의 변화는 먹이생물의 종류, 공급 및 잔류량에 의해 영향을 받는 것으로 판단된다. 외관상 건강한 개체에서는 대량 폐사를 일으킬 수 있는 세균, 바이러스가 검출되지 않았으나, 일부 안구돌출, 턱 주변 조직 출혈을 보이는 비정상 개체에서 아가미 새변의 기포 형성, 각막 조직 및 맥락막 주변 조직 괴사가 관찰되었다. 특히, 병변 부위에서 검출된 세균(P. fluorescens, Vibrio sp., V. pelagius, Planococcus maritumus 그리고 Pseudoalteromonas sp.)이 사육수에도 동일하게 분포하였으며, 사육 과정 중 외상 발생 이후 2차 세균 감염이 발생할 수 있음을 시사한다. 명태의 안정적인 양식 산업화를 위한 요소로 기초 질병 데이터 구축과 더불어 지속적인 질병관리가 필요하다.

Keywords

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