GROWTH IMPAIRMENT OF HACHERY-REARED JUVENILE WINTER FLOUNDER, pleuronectes americanus, caused by single and mixed infections of gyrodactylus pleuronecti (monogenea) and trichodina murmanica (protozoa, ciliophora)

D.E. Barker, D.K. Cone, M.D.B. Burt

Disease modelling is a priority in any pathogen prevention program for aquaculture. Extoparasites, such as Gyrodactylus (Monogenea) and Trichodina (Ciliophora) often co-occur and thrive under fish culture settings; however, it has not been determined if the effects of these parasites are synergistic or antagonistic. The present study was designed to determine if single and mixed infections of Gyrodactylus pleuronecti and Trichodina murmanica, infecting hatchery-reared juvenile winter flounder, Pleuronectes americanus, had any effect on growth and elicited any tissue response. Replicates of juvenile flounder (n=25) received one of the following treatments:  mixed inoculum of Gyrodactylus & Trichodina, Gyrodactylus inoculum, Trichodina inoculum or parasite-free (controls). The abundance of both parasites was negatively correlated with condition factor of the flounder. The parasites acted synergistically, as mean condition factor and the % change in weight was significantly lower (ANOVA, P<0.05) among fish with mixed infections compared to single infections or controls.

(Huntsman Marine Sciences Centre, 1 Lower Campus Rd., St. Andrews, New Brunswick, E5B 2L7, Canada)

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