Microscopic parasitological examination of small collections of certain Nova Scotian freshwater fish species gave the following results: Mycobacterium sp. (Eubacteria: Actinomycetes), Glugea anomola (Sporozoa: Microsporidia) and Myxosoma apeltei sp.nov. (Sporozoa: Myxosporidia) in Apeltes quadracus (Gasterosteidae): Myxosoma spp. in Gasterosteus aculeatus and Pungitius pungitius (both Gasterosteidae), Catostomus commersoni (Catostomidac), and Fundulus diaphanus (Cyprinodontidae): Myxobolus spp. (Sporozoa: Myxosporidia) in Notemegonus crysoleucas and Notropis cornutus (both Cyprinidae): Dermocystidium ovata sp.nov. (?Fungi imperfecti or ?Sporozoa: Haplosporidia) in G. aculeatus and P. pungitius: Trichodina sp. (Peritrichia: Urceolariidae) on P. pungitius.

The data suggest that for micro-parasites in wild fish populations, tissue and host specificity is the rule. Probably more parasites occur naturally in the host species examined than were recovered, some being absent from the small samples.