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Canadian Eel Subpopulations in the North American Context

This report provides an overview of Canadian eel subpopulations in the North American context. It includes data on mean discharge, annual landings, relative contribution to egg production, migration periods, and abundance indices. The report was prepared by a subcommittee of the Canadian Eel Science Working Group for the COSEWIC status review in January 2006.

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Canadian Eel Subpopulations in the North American Context

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  1. Canadian Eel Subpopulations in the North American Context Prepared by a subcommittee of the Canadian Eel Science Working Group for the COSEWIC Status Review David Cairns, John Casselman, Valérie Tremblay, François Caron, and Nick Mandrak January 2006

  2. Table 1. Mean discharge and mean annual landings (1970 - 1989) by region for the American eel continental range in Canada and the United States Mean discharge Mean annual Region (m3 sec-1) landings (t) Ontario portion of FEA1 123 Quebec portion of FEA1 431 FEA1 Total 554 St. Lawrence River Basin (includes 16,800 456 FEA1, western FEA2, and U.S. drainage to the St. Lawrence FEA2, FEA3, FEA4, FEA5 16,092 466 U.S. Eastern Seaboard 11,186 1,076 Mississippi Basina 18,434 0 American eel range not including 44,978 2.096 Mississippi Basin American eel range including 62,512 2.096 Mississippi Basin a The Mississippi Basin is considered to include the Missouri Basin

  3. Table 2. Relative contribution of American eel rearing regions to total egg production, based on the assumption that production of silver eels, by number, is proportional to mean freshwater discharge. For purposes of calculation, silver eel production in the U.S. eastern seaboard is arbitrarily set at 1,000. Excluding Mississippi Basina Including Mississippi Basin Female Silver eels (N) Eggs % of Silver eels (N) Eggs % of silver eelsb produced total egg produced total egg Region (%) Total Females (millions)c production Total Females (millions)c production St. Lawrence 100 1,502 1,502 20,025 59.2 1,502 1,502 20,025 48.8 River Basin FEA2, FEA3 97.8 1,439 1,407 9,426 27.9 1,439 1,407 9,426 23.0 FEA4. FEA5 U.S. Eastern 65.5 1,000 655 4,389 13.0 1,000 655 4,389 10.7 Seabpard Mississippi 65.5 0 0 0 0 1,648 1,079 7,232 17.6 Basin Total 3,940 3,564 33,840 100.0 5,588 4,643 41,072 100.0 a Mississippi Basin considered to include Missouri Basin b From regional means of sex ratio data compiled by Nilo and Fortin (3001). Per cent female in Mississippi Basin, where no data are available, is assumed to be the same as U.S. eastern seaboard c Fecundity for St. Lawrence River is mean of two measurements of eels from FEA1 (14.5, 13.3 million) and one from western FEA 2 (13.3 million; Tremblay 2004). Fecundity elsewhere is mean of two measurements from Gulf of St. Lawrence (6.5 and 6.9 million; Tremblay 2004)

  4. Table 3. Migration periods, mean length, and age of female silver eels exiting Canadian freshwater systems. Upper St. Lawrence R., 1 Jun-Oct 200 915 20 Casselman 2003 Lake St. Francis, vicinity 53 976 McGrath et al. 2003 of Moses-Saunders and 30 1,001 21 Tremblay 2004 Iroquois dam Richelieu R. 1 Jun-Oct 494 1,019 Dumont et al. 1998 St. Lawrence estuary 1 Sep-Oct 474 840 Couillad et al. 1997 4,529 853 Verreault et al. 2003 30 837 20 Tremblay 2004 Sud-Ouest Rivière 2 Aug-Nov 107 1,026 21 Verreault 2002 (S. shore of St. Lawrence) 30 1,043 23 Tremblay 2004 Rivière aux Pins 2 100 600 Couillard et al. 1997 Petite Trinité Rivière 2 Aug-Oct 424 650 17 Fournier & Caron 2005 (N. shore or St. Lawrence 30 679 20 Tremblay 2004 Long Pond, PEI 3 Aug-Oct 30 693 20 Tremblay 2004 Margaree Rivière, NS 3 Sep 319 642 Cairns, unpub. Topsail and Indian ponds, 4 Aug-Oct 92 694 12 Gray & Andrews 1971 Salmon R., Burnt Berry Brook Topsail Barachois, NF LaHave Rivière, NS 3 Aug-Nov 346 611 19 Jessop 1987 Migration Length Site FEAa period N (mm) Age Reference a Freshwater Ecological Areas: 1 – Great Lakes, western St. Lawrence; 2 – eastern St. Lawrence; 3 – Maritimes; 4 – Atlantic islands

  5. Table 4. Relative contributions of American eel rearing regions to total egg production, based on the assumption that production of silver eels, by weight, is proportional to mean landings for 1970-1989. For purposes of calculation, silver eel production in the U.S. eastern seaboard is arbitrarily set at 1,000 tonnes. Proportional Relative tonnage of proportion of silver eels of eggs Region produced produced (%) Ontario portion of FEA1 114 5.9 Quebec portion of FEA1 401 20.6 FEA1 total 515 26.4 FEA2, FEA3, FEA4, FEA5 433 22.2 U.S. eastern seaboard 1,000 51.3 Total 1,947 100.0

  6. Table 5. Mean values of major long-term American eel abundance indices in an early period compared with 1999-2003. Early period Recent period 1999 – 2003 Abundance Index Years Mean Mean % change Landings, ON (t) (FEA1) 1970-1977 119.32 20.84 -82.5 Silver eel landings, QC (t) 1970-1977 361.61 141.46 -60.9 (FEA1) Landings, FEA 1(t) 1970-1977 503.67 192.98 -61.7 Landings, FEA3, FEA4, FEA5 (t)a 1970-1977 512.83 352.24 -31.3 Landings, US (t) 1970-1977 1,057.06 400.38 -62.1 Moses-Saunders ladder, peak 1974-1977 13,178.18 38.42 -99.7 period index (FEA1) Bay of Quinte trawl index (FEA1) 1972-1977 1.40 0.03 -97.9 St. Nicholas fall captures (FEA1) 1971-1977 271.29 283.40 4.5 Restigouche electrofishing 1972-1977 0.48 0.67 38.5 densities (FEA3) Miramichi electrofishing 1952-1977 0.85 0.43 -49.0 densities (FEA3) Margaree electrofishing 1957-1977 3.03 0.31 -89.6 densities (FEA3)

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