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COSEWIC assessment and status report on the American Eel in Canada

Distribution

Global Range

The American eel is a catadromous species that is widely distributed in fresh waters (streams and lakes), estuaries and coastal marine waters along more than 50 degrees of latitude (from 5° to 63°) of the western North Atlantic Ocean coastline Figure 2), from Venezuela to Greenland and Iceland (Scott and Crossman 1973; Tesch 1977; Helfman et al. 1987).

Figure 2.  Global range, Lee (1980).

Figure 2.  Global range, Lee (1980).

 

CanadianRange

The historic Canadian range encompasses all accessible fresh water, estuaries and coastal marine waters connected to the Atlantic Ocean of Canada, up to the mid-Labrador coast (Figure 3). Continental shelves are used by juvenile eels arriving from the spawning grounds, and by silver eels returning to the spawning grounds. Eels regularly occur up to Hamilton Inlet-Lake Melville, Labrador (53°15’ N; 60°10’ W; Scott and Crossman 1973). However, they have also been found further north in Labrador in the English River (Kaipokok Bay: 54°58’N; 59°45’W; K.D. Clarke, DFO, pers. comm.).

Niagara Falls is the natural limit of the American eel's distribution in the Great Lakes. Occurrences reported in the upper Great Lakes watersheds (Lakes Erie, Huron and Superior) are the result of recent dispersal through the Erie and Welland canals (Scott and Crossman 1973). Such records should probably be considered as introductions (Figure 3).

Extent of occurrence (EO) for each FEA was measured according to the COSEWIC definition: the area included in a polygon without concave angles that encompasses the geographic distribution of all known components of a species. In drawing the polygons ocean migration routes and zones occupied by vagrants were not

2


Figure 3.  Canadian geographic range of the American eel (records from Mandrak and Crossman 1992).

considered. EO was measured by planimeter from Figure 3. EOs are 391,515 km2for FEA1, 546,122 km2for FEA2, 292,923 km2for FEA3, 177,586 km2(10.6%) for FEA 4, and 75,472 km2(5.4%) for FEA5. The EO for the Canadian range is 2,065,932 km2. Area of occupancy (AO) is based on aquatic habitat only. Since the American eel utilizes continental shelves during migration, a buffer of 370 km (200 nautical miles) from shore has been considered. In Lake Ontario, only the area between the shoreline and 10 m of depth has been considered. Such area of occupancy has been calculated by Verreault et al. (2004).  Areas of occupancy in km2 for FEAs 1 through 5 and for Canada are 97,400,   161,400, 635,200, 627,500, 130,700, 1,653,200 respectively.