CHARACTERISTICS OF THREESPINE STICKLEBACK (GASTEROSTEUS ACULEATUS L.) INFECTION WITH METACERCARIAE OF CRYPTOCOTYLE SPP. TREMATODES DURING THE SPAWNING SEASON IN THE WHITE SEA

A quantitative assessment of metacercariae of the genus Cryptocotyle on the body surface of threespine sticklebacks Gasterosteus aculeatus in the Gulf of Kandalaksha, White Sea, was carried out. Three spawning grounds were studied, differing in key environmental characteristics influencing spawner population densities. Fish were caught three times during the spawning period from May 29 to July 7, 2016. Early in the spawning period,the infection rates in fish from different locations were very similar, presumably indicating a mixing of sticklebacks during the wintering period. Later on, both the abundance (average number of parasites per fish, including non-infected individuals) and prevalence (the percentage of infected fish) of parasites increased towards the end of the spawning period in all the habitats. The parasite abundance and prevalence were the highest in Koliushkovaya Lagoon, which differs from other spawning grounds in being significantly isolated from the sea and having a greater retention time, favoring the accumulation of parasites in fish. The absence of sex-specific differences in the rate of infection in sticklebacks indicates that although the spatial distributions of males and females differ somewhat in some intervals of the spawning season, these differences are not great enough to have effect on infection rates. The absence of a reliable correlation between individual infection rate and body size is probably due to the high size variation in fish of different ages.