Seasonal dynamics of Posthodiplostomum cuticola (Digenea, Diplostomatidae) metacercariae and parasite-enhanced growth of juvenile host fish.

The seasonal dynamics of Posthodiplostomum cuticola metacercariae in 0+ juvenile fish, Rutilus rutilus, Scardinius erythrophthalmus and Abramis bjoerkna, was studied on the floodplain of the Dyje River, Czech Republic. Prevalence and mean abundance of P. cuticola were significantly higher in R. rutilus than in S. erythrophthalmus or A. bjoerkna. A seasonal pattern of parasite infection with maximum values in autumn was evident in all three species. No effect of overwintering on the P. cuticola infection was detected. Parasite-induced growth was found for all three fish species investigated; the fish standard length and body weight of parasitized individuals were significantly higher than those of unparasitized fish from July to October. In April, no difference was found. The maximum enhanced growth of parasitized fish was found in months with low zooplankton densities, while the difference was lower when food was abundant.