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The voluminous literature on the freshwater and diadromous fishes of Labrador is summarized in distributional maps. A total of 25 obligate freshwater spawning and one catadromous species has been reported. Fishes from Atlantic and Mississippi refugia probably invaded the region from the Great Lakes basin primarily via glacial Lake Barlow-Ojibway, crossing Quebec north of the Otish Mountain to the headwaters of the Churchill River system. Additional dispersal routes existed to the north and south. Euryhaline species from an Atlantic refugium first invaded coastal regions during postglacial depression and marine inundation. Remnants of these occur as landlocked populations. Labrador is divided into three major ichthyogeographic regions based on species distributions and dispersal opportunities. The Churchill River forms one region and is divided into three subregions. Upstream of Churchill Falls there is only one species, which dispersed across Quebec. Downstream areas, including accessible tributaries, have all of the common fishes present in Labrador. Less accessible watersheds south of Churchill River form the third subregion and are limited to fishes with better swimming abilities. The second major region is southeastern Labrador which has euryhaline fishes from Atlantic refugia and three species from Quebec. The third major region is loosely defined as northern Labrador (> 55°N) although it is one of decreasing numbers of species with increasing latitude.

During May–June 1980 and June–July 1982, six fish species exited Rivière à la Truite, a major tributary of the lower Moisie River, Quebec, in highly synchronized emigrations. Species included longnose sucker (Catostomus catostomus), white sucker (C. commersoni), lake chub (Couesius plumbeus), juvenile sea lamprey (Petromyzon marinus), Atlantic salmon (Salmo salar) parr and smolt, and anadromous brook trout (Salvelinus fontinalis). In 1980, emigration for all species except the lamprey began on 27 May and ended by 9–11 June; lamprey movements began on 4–5 June and peaked on 10 June. Similar but slightly later patterns occurred in 1982. Onset of the runs in each year coincided with declining water levels and discharge. Thus species of widely different habits exhibit similar and highly synchronized migratory patterns, possibly in response to strong changes in stream environment.

Cystidicola stigmatura (Leidy, 1886) Ward and Magath, 1917 is considered a valid species after examination of specimens from Leidy's collection. Cystidicola cristivomeri White, 1941 is considered a synonym of C. stigmatura. Cystidicola stigmatura is distinguished from the only other species in the genus, namely C. farionis Fischer, 1798, by the presence of lateral lobes on the eggs rather than filaments. A neotype of F. stigmatura is designated. Cystidicola stigmatura has not been found in fishes in the Great Lakes since 1925. The parasite was found in museum specimens of lake trout (Salvelinus namaycush) collected before 1925, suggesting that the species became rare or disappeared with the decline of lake trout in these lakes.