Cystidicola farionis (Nematoda) as an Indicator of Lake Trout (Salvelinus namaycush) of Bering Ancestry

Abstract

Cystidicola farionis Fischer is widely distributed in fishes in northern North America west of the Appalachian Mountains. The swimbladders of lake trout (Salvelinus namaycush) from 225 localities across North America were examined for the parasite but only those from the Alsek, Coppermine, Flat, Peel, Stikine, Upper Liard, and Yukon River systems were infected with mature nematodes. The ancestors of fishes in these watersheds survived glaciation in a Bering refugiurn. Thus, this strain of C. farionis probably had a refugium in Beringia in the unglaciated parts of the Yukon River system and dispersed from there into northern British Columbia and the coastal mainland of the Northwest Territories during glacial retreat.