Distribution and postglacial dispersal of freshwater fishes of Labrador

Abstract

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.