Distribution and Abundance of Mayfly Nymphs and Caddisfly Iarvae in the St. Marys River

摘要

The authors sampled benthos at a total of 166 stations in the St. Marys River to determine the distribution and abundance of mayfly nymphs and caddisfly larvae in the lower two-thirds of the river in May, August, and October 1974, and May 1975. A total of 9 mayfly and 21 caddisfly taxa were collected. Densities of mayflies (primarily the pollution sensitive Hexagenia) and caddisflies (primarily Polycentropus) ranged from 0 to more than 2000/sq m. The maximum densities were among the highest reported in the Great Lakes. Density estimates differed widely among seven geographically delineated sections of the river. In non-degraded sections of the river, densities of larval caddisflies ranged from 4 to 107/ sq m.