Vertebral Numbers of American Plaice, Hippoglossoides platessoides (Fabricius), in the Northwest Atlantic

Abstract

Vertebral numbers of American plaice in the Northwest Atlantic are compared. Counts ranged from 42 to 48 vertebrae excluding the urostylar half-vertebra.No significant difference was found between vertebral averages of males and females.Averages for an area extending from the Northeast Newfoundland Shelf southward over the whole of the Grand Bank and inshore to include St. Mary's Bay are statistically similar. The average for this area is significantly higher than averages for the Gulf of St. Lawrence, the Labrador Shelf, Flemish Cap and Fortune Bay. However, over the whole area differences are not very great, the range of averages being (for a sample of 30 or more) 45.273–45.806 vertebrae.The possible effects of differences in the time of spawning, larval drift and the inclusion of a large number of year-classes in the various samples are discussed as possible explanations for the low degree of variability in the whole area.The vertebral averages of the year-classes 1942–1953 from St. Mary's Bay are not statistically different.