DAO 37:23-31 (1999)  -  doi:10.3354/dao037023

Epizootiology of viral hemorrhagic septicemia virus in Pacific herring from the spawn-on-kelp fishery in Prince William Sound, Alaska, USA

P. K. Hershberger1,*, R. M. Kocan1, N. E. Elder2, T. R. Meyers3, J. R. Winton4

1School of Fisheries, Box 355100, University of Washington, Seattle, Washington 98195, USA
2Marrowstone Marine Station, Biological Resource Division, U.S. Geological Survey, 616 Marrowstone Point Rd., Nordland, Washington 98358, USA
3Juneau Fish Pathology Laboratory, Alaska Department of Fish and Game, PO Box 25526, Juneau, Alaska 98802, USA
4Western Fisheries Research Center, Biological Resource Division, U.S. Geological Survey, 6505 NE 65th St., Seattle, Washington 98115, USA

ABSTRACT: Both the prevalence and tissue titer of viral hemorrhagic septicemia virus (VHSV) increased in Pacific herring Clupea pallasi following their introduction into net pens (pounds) used in the closed pound spawn-on-kelp (SOK) fishery in Prince William Sound, Alaska. VHSV was also found in water samples from inside and outside the SOK pounds after herring had been confined for several days; however, water samples taken near wild free-ranging, spawning herring either failed to test positive or tested weakly positive for virus. Little or no virus was found in tissue samples from free-ranging, spawning herring captured from the vicinity of the pounds, nor did the prevalence of VHSV increase following spawning as it did in impounded herring. The data indicated that increased prevalences of VHSV were correlated with confinement of herring for the closed pound SOK fishery and that infection was spread within the pounds through waterborne exposure to virus particles originating from impounded fish. In addition, pounds containing predominantly young fish had higher prevalences of VHSV, suggesting that older fish may be partially immune, perhaps as a result of previous infection with the virus. Operation of SOK pounds during spawning seasons in which young herring predominate may amplify the disease and possibly exacerbate the population fluctuations observed in wild herring stocks.

KEY WORDS: VHSV · Virus · Herring · Epizootiology · Disease

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