Changes in levels of infection with Schistocephalus solidus (Muller 1776) of the three-spined stickleback Gasterosteus aculeatus (Actinopterygii: Gasterosteidae) from the Gdynia Marina

This paper analyses the changes in the level of infection with the freshwater parasite Schistocephalus solidus of the three-spined stickleback from the Gdynia. Marina. Environmental factors such as salinity, pollution and eutrophication or the presence of other species affect the transmission of parasites. infection indices have been increasing since the 1990s. Differences in the infection level of morphological forms were also found: this may be due to their environmental preferences.