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Diseases of Aquatic Organisms

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DAO 90:1-14 (2010)  -  DOI:

Failure of population recovery in relation to disease in Pacific herring

Gary D. Marty1,4,*, Peter-John F. Hulson2, Sara E. Miller2, Terrance J. Quinn II2, Steve D. Moffitt3, Richard A. Merizon3

1Department of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California, 1 Shields Ave., Davis, California 95616-8732, USA
2Juneau Center, School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 17101 Pt. Lena Loop Rd., Juneau, Alaska 99801, USA
3Alaska Department of Fish and Game, PO Box 669, Cordova, Alaska 99574-0669, USA
4Present address: Animal Health Centre, Ministry of Agriculture and Lands, 1767 Angus Campbell Rd., Abbotsford, British Columbia V3G 2M3, Canada

ABSTRACT: Following an estimated 60% decline in population abundance in early 1993, recovery of the Pacific herring Clupea pallasii population of Prince William Sound, Alaska, USA, has been impaired by disease. Comprehensive epidemiological study from 1994 through 2002 validated an age-structured assessment (ASA) model of disease and population abundance; from 2003 to 2006, the impact of disease was modeled by analyzing only 2 lesions: ulcers and white foci in the heart. The ASA model identified increased natural mortality since 1993 that can be explained by (1) epidemics associated with ulcers (prevalence about 3%) and the North American strain of viral hemorrhagic septicemia virus (VHSV Type IVa; prevalence up to 14%) in 1994 and 1998 and (2) relatively high prevalence of the mesomycetozoean Ichthyophonus hoferi from 1994 through 2006, including epidemics with the greatest sample prevalence in 2001 (38%, by histopathology) and 2005 (51%, estimated histopathology prevalence). Fourteen other parasites occurred at prevalence >10%, but none were considered significant contributors to fish mortality. We predict that if natural mortality after 1994 had returned to background levels that best fit the model from 1980 to 1992 (0.25 yr–1), population biomass in 2006 would have been 3 times the best estimate, despite relatively poor recruitment since 1994. In conclusion, disease information can be used to explain and predict changes in populations that have confounded traditional fisheries assessment.

KEY WORDS: Pacific herring · Clupea pallasii · Viral hemorrhagic septicemia virus · VHSV Type IVa · Ulcers · Ichthyophonus hoferi · Age-structured assessment model · Population-level response

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Cite this article as: Marty GD, Hulson PJF, Miller SE, TJ Quinn II, Moffitt SD, Merizon RA (2010) Failure of population recovery in relation to disease in Pacific herring. Dis Aquat Org 90:1-14.

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