Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Parasites of fish in Finland. VI. Nematodes.

Abstract

In a survey conducted between 1973 and 1979, 23 nematode species were identified in fish from Finland. The material, consisting of 2922 specimens of 34 species of fish, was sampled in brackish water in the northern Baltic region as well as in freshwater; farmed fish were also studied. Sampling was extensive in one brackish water area and at one freshwater site. Most of the adult parasites occurred in only one or a very restricted number of fish species. Infective larvae were frequently recorded in numerous fish species. Species which reach sexual maturity in fish frequently had a marked seasonal occurrence due to the prevailing temperature. The parasite fauna is considered with regard to salinity, the geological history of Fennoscandia and fish migration. The nematodes were studied by light and scanning-electron microscopy and are described and figured; the biology and life-histories of the parasites are discussed.