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Diseases of Aquatic Organisms

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DAO 77:149-158 (2007)  -  DOI:

Infection of wild fishes by the parasitic copepod Caligus elongatus on the south east coast of Norway

P. A. Heuch1,*, Ø. Øines1, J. A. Knutsen2, T. A. Schram3

1National Veterinary Institute, Section for Parasitology, PO Box 8156 Dep., 0033 Oslo, Norway
2Institute for Marine Research, Flødevigen Research Station, 4017 His, Norway
3Department of Biology, University of Oslo, PO Box 1066 Blindern, 0316 Oslo, Norway

ABSTRACT: Natural Caligus elongatus Nordmann infections of wild coastal fishes on the Norwegian south east coast were monitored at various times of the year from 2002 to 2004. The prevalence for all coastal fish (n = 4427) pooled was 15%, and there were great differences between fish species and seasons. Lumpfish Cyclopterus lumpus L. spawners were the most infected fish, with a prevalence of 61% and a median intensity of 4 lice fish–1, whereas gadids had a mean prevalence of 19% and a median infection of 1 to 2 lice fish–1. Sea trout Salmo trutta L. and herring Clupea harengus L. carried C. elongatus at prevalence values of 29 and 21%, respectively. The results were compared with infection data for immature North Sea lumpfish. Lumpfish spawners caught on the coast in March to April had fewer lice than North Sea lumpfish in July. Spawners carried mostly adult lice, as did coastal fish hosts in May to June. The low development rates of lice at low spring temperatures and new genetic data suggest that the May to June adult lice could not have been offspring of the March to April lice, indicating transfer of adult lice to coastal fish. Most coastal fish species appeared to acquire new C. elongatus infections between May to June and September. The relatively high numbers of chalimii on North Sea lumpfish suggest that offshore fish sustain an oceanic population of this louse species.

KEY WORDS: Infection routes · Sea lice · Lumpfish · Gadidae · Seasons

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Cite this article as: Heuch PA, Øines Ø, Knutsen JA, Schram TA (2007) Infection of wild fishes by the parasitic copepod Caligus elongatus on the south east coast of Norway. Dis Aquat Org 77:149-158.

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