Patterns of Ichthyobodo necator sensu stricto infections on hatchery-reared Atlantic salmon Salmo salar in Norway
Journal article, Peer reviewed
Permanent lenke
http://hdl.handle.net/11250/109130Utgivelsesdato
2010-02-17Metadata
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Originalversjon
http://dx.doi.org/10.3354/dao02173Sammendrag
Infection patterns with ectoparasitic flagellates belonging to the genus Ichthyobodo
were studied in an Atlantic salmon Salmo salar (L.) hatchery in western Norway during an 11 mo
period, from eyed eggs to smoltification. Since the earlier species designation Ichthyobodo necator
(sensu lato, s.l.) has been shown to represent a complex of several species, the epizootiology of different
Ichthyobodo spp. is poorly known. Therefore, we employed molecular methods to ascertain the
specific identity of the parasites detected in our study. Only I. necator in the recently redefined and
restricted sense occurred (I. necator sensu stricto, s.s.). We observed a 2-peak pattern of infection; the
first peak occurred among fry in March and the second peak among fingerlings and pre-smolt in
August and September. Skin lesions observed on fingerlings and pre-smolt were significantly associated
with Ichthyobodo infections. Also, these infections were negatively correlated with both haematocrit
values (Hct) and the condition factor (K) of the fish. The patterns of infection on the farmed
salmon suggest that I. necator s.s. is an opportunistic parasite of salmon, flourishing in periods when
susceptible hosts are present and the environment favours parasite proliferation. Our study is the first
to detect and identify I. necator s.s. on wild-caught adult salmonids (brown trout S. trutta L.). Wild
salmonids and sticklebacks Gasterosteus aculeatus (L.) caught in the lakes serving as a water supply
to the hatchery were found infected with I. necator s.s., hence these are the likely sources of parasites
entering the hatchery via the inlet water.