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Geomatics to the rescue of the
American Eel

DFO  S. Blais

The American Eel population in North America has fallen sharply over the last 30 years, particularly in the Great Lakes and the St. Lawrence watershed. What has caused this situation and what can be done to remedy it? Geomatics can help us find answers to these questions.

Although researchers have not been able to determine the causes for the decline in the eel population with certainty, the most recent studies indicate that fishing, contaminants and dams appear to be the principal factors that, when combined, may have led to the drop in the number of breeding eels.

Dams and other obstacles built on watercourses are threats to young eels swimming upstream since they reduce or block access to growing sites upstream. As for hydroelectric dam turbines, they kill large numbers of mature adults making their way to breeding sites in the Atlantic.

A modern tool to the rescue of the American Eel

Fisheries and Oceans Canada, in collaboration with the Ministère des Ressources naturelles et de la Faune du Québec and the Ontario Ministry of Natural Resources, has developed a geographic information system (GIS) to aid in decision making. This system allows managers to spot sites where the eel no longer has unobstructed access to its natural habitat and to determine where migratory passes need to be built to facilitate the passage of the fish and foster the recovery of this species. By using geomatics, the impact of various management scenarios for the dams in the watershed can be analyzed visually.

Here, the Web tool designed by Fisheries and Oceans Canada illustrates the habitat gains that would result if eels were able to bypass an obstacle on Rivière Rimouski.

Natural Resources Canada offered its expertise in geomatics and provided the data held in its National Hydro Network GeoBase. These data describe water bodies such as lakes, reservoirs, rivers and streams throughout Canada and indicate the direction of water flow. Once entered into the geographic information system (GIS), these data allow managers to calculate the gains that would result in terms of the increased size of fish habitat available upstream and downstream after a migratory pass has been built.

The next steps

For now, the tool is in development and pilot projects are being conducted on three rivers: one in Quebec, one in Ontario and one in the Maritimes. The next steps will be to train environmental analysts so they can use the tool, and to perfect the functions of the Web tool. The developers will also add data so that other priority watersheds can be documented. In the near future, the geographic information system will be used not only to determine intervention priorities for the eel, but also for other migratory fish species.

Patrick Dupont
Oceans, Habitats and Species at Risk