EMERGENCE OF CADDISFLIES (TRICHOPTERA) FROM ERODING AND NON-ERODING SHORELINES OF SOUTHERN INDIAN LAKE, MANITOBA, CANADA

Abstract

AbstractEmerging Trichoptera were collected from the littoral zone of a newly-created reservoir, Southern Indian Lake, Manitoba, from 1977 to 1981. The relationship between caddisfly emergence and lake shoreline type, depth of sampling, and shoreline erosion rate was studied. Twenty-five species of Trichoptera were collected; six species of Polycentropodidae comprised almost 75% of the total number of individuals. Abundance and richness of Trichoptera were correlated with shoreline stability, with higher abundance and richness being found at more stable (i.e. lower erosion) shorelines. Highest numbers of Trichoptera emerged in 1981, 5 years after impoundment. Maximum abundance and richness of Trichoptera was found at 3.5 m depth, which is also the depth at which maximum deposition of organic matter occurred. Agrypnia straminea Hagen, a case-maker, dominated the trichopteran fauna at the marsh shoreline; species of net-spinning Polycentropodidae dominated at the clay shorelines. Patterns of species composition and abundance in 1982 artificial substrate collections were similar to those found in 1977–1981 emergence trap collections. Interspecific differences in Neureclipsis capture nets may explain the greater abundance of N. validus (Walker) than N. bimaculatus (L.) at a high erosion shoreline.