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COSEWIC assessment and status report on the American Eel in Canada

Technical summary

 

Anguilla rostrata
american eel       anguille d’Amérique
Rangeof Occurrence in Canada: Accessible freshwater, estuaries, and sheltered salt water of Newfoundland, Nova Scotia, Prince Edward Island, New Brunswick, Quebec and Ontario to Lake Ontario and lower Niagara River. Continental shelves are also used by migrating juvenile and silver eels. The northern limit in Canadian waters is the Hamilton Inlet-Lake Melville estuary of Labrador.

Freshwater Ecological Areas (following the COSEWIC national system):

FEA1: Great Lakes-Western St. Lawrence (Ontario and western and central Quebec)
FEA2: Eastern St. Lawrence (eastern Quebec)
FEA3: Maritimes (New Brunswick, Nova Scotia, Prince Edward Island, and the central and southern parts of Quebec's Gaspé Peninsula)
FEA4: Atlantic Islands (Newfoundland)
FEA5: Eastern Arctic (Labrador)

 

Extent and Area InformationFEA1FEA2FEA3FEA4FEA5SPECIES
 Extent of occurrence (EO)(km²) -based on polygons see text -  Canadian Range391,515546,122292,923177,58675,4722,065,932
 ·         Specify trend in EODeclineDecline?Increase?Stable ?Stable ?Decline
 ·         Are there extreme fluctuations in EO?NoNoNoNoNoNo
 Area of occupancy (AO) (km²)-based on Lake Ontario 0-10m area, Verreault et al. 2004 for Quebec, Museum records for Ontario, and Canadian waters outer limit (buffer of 370 km)97 400161 400635 200627 500130 7001 653 200

 

 

·         Specify trend in AODeclineDecline?Stable ?Stable ?Stable ?Decline
 ·         Are there extreme fluctuations in AO?NoNoNoNoNoNo
 ·         Number of known or inferred current locationsUnknownUnknownUnknownUnknownUnknownUnknown
 ·         Specify trend in #DeclineDecline?Stable ?Stable ?Stable ?Decline
 ·         Are there extreme fluctuations in number of locations?NoNoNoNoNoNo
 ·         Specify trend in area, extent or quality of habitatDeclineDecline?Stable?Stable?Stable?Decline
Information for eel componentsFEA1FEA2FEA3FEA4FEA5SPECIES
 Generation time (average age of parents in the component). Ranges refer to parental ages of eels reared in salt and fresh water, respectively229-229-229-229-229-23
 ·         Number of mature individuals424,000 in 1997UnknownUnknownUnknown UnknownUnknown
 ·         Trends in components:DeclineDecline?Increase?UnknownUnknownDecline
 

·         % decline over the last 10 years or 3 generations

Note: No data are available for changes over 3 generations of female fresh-reared eel, which is approximately 66 years. Data in this row are from Table 5. Reported landings in FEA3-5 declined by 26.2% over ~1 freshwater gen. and ~3 saltwater gen.  Data from Ontario reflect the upper St. Lawrence/Lake Ontario part of FEA1.  Data series from Quebec reflect the whole FEA1 population.

FEA 1 may supply ~27-67% of global spawn output (see text Contribution of the St. Lawrence eel population) - a > 90% decline in this area may indicate a loss of 25-60% of the global spawn.  The calculations are based on unproven methodologies and may be an overestimate; for that reason a range of values is given.

See Table 5  1Landings 2ladder index *Elecrofishing densities over 1-2 generations, 3Electrofishing counts over 1 generation.

Also landings in FEA 3-5 declined ~26%

Ontario ~ 98.8% (Quinte trawl index)
99.5% (Moses-Saunders ladder index)
Quebec  ~15.1% (St. Nicholas index)
~63.9% (Quebec silver eel landings, ~1 generation
UnknownRest. +74.8%* Miramichi ~43%*Margaree ~87.9%* Stewiake ~81.6%3 Elsewhere UnknownUnknownUnknownUnknown
 ·         Are there extreme fluctuations in number of mature individualsNoUnknownNoUnknownUnknownUnknown
 ·         Is the total component severely fragmented?NoNoPartlyUnknownUnknown No
 ·         Specify trend in number of components / subcomponentsDeclineStableStableStableStableDecline (FEA1)
   ·         Are there extreme fluctuations in number of components / subcomponents?NoNoNoNoNoNo
ThreatsFEA1FEA2FEA3FEA4FEA5SPECIES
 ·         Actual      
 

·         Loss of habitat (dams)

·         Turbine mortality

·         Fisheries

·         Contamination

·         Change in oceanic currents

·         Parasites - Anguillicola crassus

·         Low pH

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X


Rescue Effect (immigration from outside source)  Not ApplicableFEA1FEA2FEA3FEA4FEA5SPECIES
 Status of outside component(s)? USA:Rescue effect is not applicable since this is a catadromous, panmictic species, all components breed in one area (see text – Rescue Effect)N/AN/AN/AN/AN/A67.5% decline in reported US landings since 1970s
 ·         Is immigration known or possible?YesYesYesYesYesYes
 ·         Would immigrants be adapted to survive in Canada?YesYesYesYesYesYes
 ·         Is there sufficient habitat for immigrants in Canada?YesYesYesYesYesYes
 ·         Is rescue from outside components likely? – yes, but not really applicable – see note aboveYesYesYesYesYesYes
Quantitative AnalysisNo DataNo DataNo DataNo DataNo DataNo Data

Existing Status

NatureServe Status [NatureServe (2005) last revised in 1996; see also Table 7]
Global G5
National         US - N5
                       Canada - N5
Regional: US- AL- S5, AZ - SNA, AR - S4, CT - S5, DE - S5, DC - S4, FL - SNR, GA -S3S4, IL - S2, IN - S4, IA - S3?, KS - S2, KY - S4S5, LA ‑ S5, ME - S5, MD - S4,
MA -S5, MI - SNA, MS - S5, MO - SNR, NE - SNR, NY - SNA, NH - S5, NJ - S5, NM - SX,  NY - S5, NC - S5, OH - SNR, OK - S3, PA - S5, RI - S5, SC - SNR, SD - 3?, TN - S3, TX - S5, VT - S3, VA - S5, WV - S2, WI - S1S2 . 
N.B. the US is currently reviewing the status of this species for possible listing under the Endangered Species Act.
Canada: LB - S4, NB - S5, NF - S5, NS - S5, ON - S5, PE - S4S5, QC - S3
Wild Species 2000 (Canadian Endangered Species Council 2001)
National - N6
Provincial - N – 4*, QC -3, NB - 4, NS -4, PE - 4, LB - 4, NF - 4

*Dextrase indicated that this should be 2 (A. Dextrase, Ontario Ministry of Natural Resources, Peterborough, Ontario; annotated rank comments in relation to the data output for the Wild Species web site resulting from the November 2001 query for freshwater fish species).

COSEWIC
First assessed in 2006 as Special Concern.

Status and Reasons for Designation

Alpha-numeric code:  not applicable
Status: Special Concern
Reasons for Designation: Indicators of the status of the total Canadian component of this species are not available. Indices of abundance in the Upper St. Lawrence River and Lake Ontario have declined by approximately 99% since the 1970s. The only other data series of comparable length (no long-term indices are available for Scotia/Fundy, Newfoundland, and Labrador) are from the lower St. Lawrence River and Gulf of St. Lawrence, where four out of five time series declined.  Because the eel is panmictic, i.e. all spawners form a single breeding unit, recruitment of eels to Canadian waters would be affected by the status of the species in the United States as well as in Canada. Prior to these declines, eels reared in Canada comprised a substantial portion of the breeding population of the species. The collapse of the Lake Ontario-Upper St. Lawrence component may have significantly affected total reproductive output, but time series of elver abundance, although relatively short, do not show evidence of an ongoing decline. Recent data suggest that declines may have ceased in some areas; however, numbers in Lake Ontario and the Upper St. Lawrence remain drastically lower than former levels, and the positive trends in some indicators for the Gulf of St. Lawrence are too short to provide strong evidence that this component is increasing.  Possible causes of the observed decline, including habitat alteration, dams, fishery harvest, oscillations in ocean conditions, acid rain, and contaminants, may continue to impede recovery.

Applicability of Criteria

Criterion A: (Declining Total Population):  Not Applicable. The Canadian segment of the population in the Great Lakes/Upper St. Lawrence Basin has declined by approximately 99% since the 1970s (based on landings, ladder indices, and test fishing indices), and is continuing to decline for reasons that are not well understood and may not be reversible. Decline has also been documented at four of five sites in the lower St. Lawrence and Gulf of St. Lawrence; however, the overall decline in Canadian waters is unknown
Criterion B: (Small Distribution, and Decline or Fluctuation): Not applicable – EO and AO exceed threshold values.
Criterion C: (Small Total Population Size and Decline): Not applicable - Total population size although unknown is undoubtedly well above the threshold value.
Criterion D: (Very Small Population or Restricted Distribution): Not applicable – the species is widespread and numerous, threshold values are exceeded.
Criterion E: (Quantitative Analysis): Not applicable – no data.