Freshwater Macroinvertebrates and Their Habitats in Dominica

Abstract

A survey of macroinvertebrates inhabiting freshwater habitats of Dominica was conducted from 1995 to 2005. Qualitative collections were made by sweeping a dip net through the water column, agitating the bottom substrate, and by hand examination of rocks, plants, and debris submerged in both standing and flowing bodies of water across the island. Water temperature and elevation were also recorded at each site. Ecological conditions were generally suitable to support many groups of freshwater macroinvertebrates, although high water temperatures, suspected low dissolved oxygen concentrations, and low pH values at some sites may have limited some populations. These collections yielded at least 62 taxa, 29 of which are reported for the first time from Dominica, bringing the total number of freshwater macroinvertebrates known from this island to 116. Dominant taxa collected included gastropods, ephemeropterans, odonates, hemipterans, trichopterans, and dipterans. Waterfalls, which were thought to act as barriers to upstream movement of non-flying invertebrates, appear not to limit the distribution of most decapods, but may impede nerite snails. Generally the freshwater macroinvertebrate fauna of Dominica is sparse, most likely due to the oceanic origin of the island and challenges colonizing such a habitat.