Watching Recovering Mussels in Ontario’s Ausable River

November 2007

Few people realize that freshwater mussels are the world’s most endangered species group. The mussel is a veritable “canary in a coalmine.” Amongst other things, mussels require good water quality to thrive, so their presence or absence is a clear indicator of the health of the river or lake they call home. And the sad reality is that they are disappearing from lakes and rivers across North America.

The Ausable River, which winds through some of Canada’s best farmland near London in southwestern Ontario, is remarkable in terms of its species diversity. In fact, it is one of the richest watersheds, for its size, in Canada. It supports 26 mussel species; however, six of those are considered species at risk, with five listed nationally as “Endangered” and one as “Threatened.” As well, many of the species at risk in the Ausable are found at only a few locations in Canada, and several are globally rare.

The Ausable River Recovery Team was formed to develop and implement a recovery strategy to ensure the continued survival of the species at risk in the river. Co-chaired by the Ausable Bayfield Conservation Authority (ABCA) and Fisheries and Oceans Canada (DFO), the team’s other partners include the Ontario Government, Environment Canada, Royal Ontario Museum, county stewardship councils, and three universities (Lakehead, Guelph and Windsor). One of the team’s urgent priorities was to implement a long-term monitoring program to assess the current numbers and diversity of mussels across the Ausable River watershed.

The results of the monitoring delivered some welcome and startling news. It was known that the endangered Northern Riffleshell had disappeared from 95% of its range in North America, with only three reproducing populations thought to be left in the world. But now a fourth is known to exist, because the survey found juvenile Northern Riffleshells in the Ausable, indicating recent reproduction. Another endangered mussel, the Snuffbox, was found in much greater numbers than expected. Previous surveys had found only a solitary Snuffbox. There was equally good news about the Wavyrayed Lampmussel, another endangered species. Its population was found to be much healthier than previously thought, with live animals encountered where previously only shells had been reported.

Indeed, the numbers indicated that there is a higher density of some species at risk in the Ausable than in the Sydenham River, which is generally considered to be Canada’s premier mussel river for species at risk and overall species richness. The Ausable is a biodiversity treasure house, making it a nationally significant watershed for preserving native freshwater mussels.

The Ausable River Mussel Survey is not only a vivid reminder of the interconnectedness of the ecosystem, but underscores, as well, the power of partnerships between science and stewardship in preserving biodiversity.