A morphological examination of sympatric cisco forms in four lakes with specific reference to the occurrence of shortjaw cisco (Coregonus zenithicus) in Manitoba

Abstract

The shortjaw cisco (Coregonus zenithicus) is a widespread species ranging from the Great Lakes region, northwest to Great Slave Lake. Beyond the Great Lakes region, the validity of this species has been questioned due to genetic and morphological variability. Ciscoes were collected from four lakes reported to contain putative C. zenithicus (Lake Athapapuskow, George Lake, and Clearwater Lake, MB; and Reindeer Lake, SK). An examination of gillraker count and arrangement, jaw position, body size, and dorsal colouration was used to initially identify cisco forms within each lake. Multivariate analyses including Principal Component Analysis and Discriminant Analysis incorporating additional meristic and morphometric characters were used to examine within-lake and between-lake variation. Sympatric low and high gillraker forms were found within each lake. The low forms were found to conform to populations of C. zenithicus reported in the literature and the high forms were found to be consistent with descriptions of C. artedi.