The Peel River basin is a unique Canadian glacial refugium containing many relict fish populations. Peel River is presently tributary to the Mackenzie River system, but at least twice during Pleistocene glaciations it was diverted into headwaters of the Yukon River system, offering the possibility of two-way transfer of aquatic organisms between the Mackenzie and Yukon. Present fish distributions in the Peel basin are summarized. Biochemical and morphological evidence suggests that races of at least six species now inhabiting the area (Coregonus clupeaformis, Prosopium coulteri, Thymallus arcticus, Salvelinus namaycush, Esox lucius, Cottus cognatus) originated from types which either came from the Yukon River system or developed in situ in unglaciated parts of the Peel.
Late cenozoic geology, Ancient Pacific Margin NATMAP Project, report 3: a re-evaluation of glacial limits in the Stewart River basin of Stewart River map area, Yukon Territory