Discrimination of the Endangered Atlantic Whitefish from Lake Whitefish and Round Whitefish by Use of External Characters

Abstract The scope of phenetic variation exhibited by populations of lake whitefish Coregonus clupeaformis in the Canadian Maritime Provinces is not known, which complicates the task of accurately identifying specimens of the endangered Atlantic whitefish C. huntsmani. We developed criteria for accurate (≥95% correct classification) species discrimination using morphological data acquired from archival and recent coregonid collections from the Maritime Provinces. We used discriminant function analyses to assess (1) the usefulness of Atlantic whitefish external typological characters in accurately identifying species, (2) the temporal stability of reportedly diagnostic characters, and (3) which morphological characters could be used to accurately identify these coregonids to species. Not all external typological characters were robust in the discrimination of recent Atlantic whitefish and lake whitefish collections. Several previously identified diagnostic characters exhibited significant temporal variation but remained robust in species discrimination. Species-specific differences for the number of lateral line scales, mouth position, and proportional pectoral fin length could be used concomitantly for accurate (≥95% correct classification) identification of coregonid species in the Canadian Maritime Provinces. Atlantic whitefish possessed a significantly (P < 0.001) greater number of lateral line scales (range = 90–102; mean ± SD = 93.79 ± 2.70) than lake whitefish (range = 66–91; mean = 77.18 ± 4.21), a significantly (P < 0.01) shorter pectoral fin than lake whitefish (11% and 16% of fork length, respectively), and a significantly (P < 0.001) more terminal mouth than lake whitefish (ratio of upper jaw to lower jaw: mean ± SD = 0.98 ± 0.07 and 0.82 ± 0.06, respectively). These characters can also be used to distinguish between Atlantic whitefish and round whitefish Prosopium cylindraceum collected in the Maritime Provinces.