Morphological and Ecological Divergence Within the Lake Whitefish (Coregonus clupeaformis) Species Complex in Yukon Territory

Abstract

Two forms of lake whitefish (Coregonus clupeaformis species complex sensu McPhail and Lindsey [1970]) were found in each of five lakes in Yukon Territory. They are characterized by differences in gill raker counts. Low gill raker fish are benthic feeders and are found almost exclusively near the bottom while high raker fish are largely plankton feeders, being found throughout the lake water column. High raker fish have longer and more closely spaced gill rakers than low raker fish. They also have shorter life spans and mature earlier than low raker fish. Lakes supporting these sympatric populations of lake whitefish have no cisco populations. The low gill raker member of these sympatric populations seems to be equivalent to most other Yukon lake whitefish whereas the high raker member appears to be the unusual member of each sympatric pair. Key words: whitefish, lake, feeding, morphology, growth, divergence, Yukon Territory, sympatric populations