POPULATION-DYNAMICS AND ECOPARASITOLOGICAL SURVEYS OF COROPHIUM VOLUTATOR IN COASTAL WATERS IN THE BAY-OF-MECKLENBURG (SOUTHERN BALTIC SEA)

The population dynamics of Corophium volutator (Pallas, 1766) were stu died at 2 stations in virtually tideless water in the Bay of Mecklenbu rg (southern Baltic Sea). Particular attention was given to temperatur e, the main factor affecting reproductive and development processes. I nfestation by parasites was one of various factors which was considere d for explanation of variations in abundance in the course of the year . At both stations 2 generations were present during the reproduction period. These were called the spring generation and summer generation (with cohorts I and II) in accordance with their occurrence. The great est increase in abundance coincided with the appearance of the spring generation. Most of the overwintering individuals originated from summ er generation I in both populations. Although reproductive activity wa s the same at both stations, the variations in abundance were complete ly different; the population at one station collapsed almost completel y. Ecoparasitological analysis revealed that mortality in the extremel y heavily infested spring generation was unusually high, and this had a direct impact on subsequent reproductive processes. The much more se vere infestation at one station than at the other was found to be caus ed by a 4-fold higher abundance of the wadden snail Hydrobia spp., whi ch is the primary intermediate host of the larval trematodes found in C. volulator in these waters. The studies showed that parasite infesta tion is a factor that can affect population development. Therefore, ec oparasitological phenomena should be taken into account when interpret ing data relating to population dynamics.