By Sonia Trentin and Patrick Dupont
American eel (Source: Quebec Department of Natural Resources and Wildlife)
There has been a significant decline in the American eel population in Canada and the United States over the past 30 years. This population decline is particularly evident in the Great Lakes and St. Lawrence River basin where eel fishermen have seen a dramatic drop in catches. To determine the cause of the decline and identify the action to be taken, researchers have turned to geomatics and data from the GeoBase National Hydro Network.
Causes of the Decline in the Eel Population
Although the cause of the decline in the American eel population could not be determined with certainty, the most recent work suggests that fishing, contaminants and dams are the main culprits and that all of these factors combined have resulted in a decline in the number of spawning eels.
Dams and other barriers in streams pose a threat to the upstream migration of young eels by reducing or preventing access to upstream growth habitats, while turbines in hydro dams kill large numbers of mature eels on their downstream migration to their spawning areas in the Atlantic Ocean.
A Modern Tool for Addressing the Decline in Eels: Geographic Decision-Support System
Web tool developed by Fisheries and Oceans Canada (Source: Fisheries and Oceans Canada)
Fisheries and Oceans Canada, in collaboration with the Quebec Department of Natural Resources and Wildlife and the Ontario Ministry of Natural Resources, has developed a geographic decision-support system (GDSS) for evaluating sites where the American eel no longer has free access to its natural habitat. The GDSS is helping to determine where fish ladders should be installed to facilitate eel movement past dams and to promote the species’ recovery. According to Fisheries and Oceans Canada, the use of geomatics is now critical to allowing a visual analysis of the impact of the various dam construction scenarios.
Natural Resources Canada (NRCan) has offered its expertise in geomatics and has provided data from the GeoBase National Hydro Network (NHN) describing the various entities across Canada, such as lakes, reservoirs, rivers and streams, and indicating the direction of flow. Once the data are entered into the decision-support system, the gain in the area of upstream and downstream habitat following construction of a fish ladder can be calculated.
“The project to calculate habitat loss caused by the presence of the dams in a river system has validated our data and identified strengths and weaknesses,” says Denis Boutin of NRCan’s Centre for Topographic Information - Sherbrooke. “One of our concerns is to ensure that our numerical data truly meets the needs of users so that the data can play a key role in monitoring issues, such as water management and sustainable development of natural resources.”
For now, the GDSS computer tool is still in the development stage and pilot projects are underway to document three rivers — one in Quebec, one in Ontario and one in the Maritimes. The next step will be to train environmental analysts on the use of the tool and to fine tune the features of the Web tool. Additional data provided by the National Hydro Network will also be added to document other watersheds that are considered priorities. In the near future, the geographic decision-support system will be used not only to determine priorities for action for eels, but also for other migratory fish species.
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