The population dynamics ofLernaeocera lusci andL. branchialis on intermediate hosts

The metapopulation dynamics ofLernaeocera lusci andL. branchialis on soleSolea solea and flounderPleuronects flesus were studied in the Dutch coastal area. Both fish species harboured large numbers of parasites when they arrived in the coastal area in the spring. Between April and June all parasites detached from the intermediate hosts and infected the definitive hosts (0+ whitingMerlangius merlangus forL. branchialis, and possibly sand gobyPomatoschistus minutus forL. lusci). Thereafter, flounder remained almost parasite-free until autumn. This suggests thatL. branchialis has only 1 generation per year. However, soles were infested again withL. lusci (in June and July), which detached to infest 0+bibTrisopterus luscus, the typical definitive host for this parasite species. Thus, it appears thatL. lusci has 2 generations per year. The flounder length and the infection intensity ofL. branchialis were not correlated throughout the study period. Significant positive correlations were found between the sole length and infection intensity ofL. lusci in late spring, but not in the summer or autumn. Throughout the year, bothL. lusci andL. branchialis were aggregated within their intermediate host populations (variance ≫ ≫ abundance).