Infection of wild fishes by the parasitic copepod Caligus elongatus on the south east coast of Norway
2007
Natural Caligus elongatus Nordmann infections of wild coastal fishes on the Norwegiansouth east coast were monitored at various times of the year from 2002 to 2004. The prevalence for allcoastal fish (n = 4427) pooled was 15%, and there were great differences between fish species andseasons. Lumpfish Cyclopterus lumpus L.spawners were the most infected fish, with a prevalence of61% and a median intensity of 4 lice fish–1, whereas gadids had a mean prevalence of 19% and amedian infection of 1 to 2 lice fish–1. Sea trout Salmo trutta L. and herring Clupea harengus L. carriedC. elongatus at prevalence values of 29 and 21%, respectively. The results were compared with infectiondata for immature North Sea lumpfish. Lumpfish spawners caught on the coast in March to Aprilhad fewer lice than North Sea lumpfish in July. Spawners carried mostly adult lice, as did coastal fishhosts in May to June. The low development rates of lice at low spring temperatures and new geneticdata 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 chalimiion North Sea lumpfish suggest that offshore fish sustain an oceanic population of this louse species.
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