Decline of Gomphus fraternus fraternus (Odonata: Gomphidae) in Lake Erie

Abstract

Collections and literature reports indicate that Gomphus fraternus fraternus was abundant on the shoreline of Lake Erie prior to 1960, and "tens of thousands" were reported at Long Point Bay. After 1960 there were no reports from the shoreline, although there have been a number of comprehensive studies that have included the shoreline area and a number of Odonata specialists have also visited the Lake Erie shoreline regularly. A survey of portions of the Lake Erie shoreline, including the Long Point Bay area in 1999 and 2000, during the established peak and late peak flight period in southwestern Ontario, did not result in any observations. It is concluded that G. fraternus has declined substantially in Lake Erie and is possibly extirpated from the lake. The decline appears to have occurred between 1950 and 1960, and thus approximates the mid-1950s decline of burrowing mayflies in Lake Erie, which has been associated with warm weather oxygen depletion and pollution. Although it may never be possible to precisely determine the cause of the decline of G. fraternus, it is likely that a number of factors are involved including climatic warming, pollution, changes to the shoreline, other effects of shoreline development, and introduced species.