COSEWIC assessment and status report on the American Eel in Canada
- Assessment Summary
- Executive Summary
- Species information
- Population size and trends
- 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)
- Contribution of the St. Lawrence Eel Component – Landings Method
- Rescue effect
- Limiting factors and threats
- Special significance of the species
- Technical summary
- Information sources
- Biographical summaries of the report writers
- Collections examined
FEA3 - Maritimes (New Brunswick, Nova Scotia, Prince Edward Island, and the central and southern parts of Quebec's Gaspé Peninsula)
Figure 15. Data sites within the ecological freshwater area FEA3, Maritimes.
Indices of Recruitment
Estimates of elver influx into rivers are available for two Nova Scotian sites. The East River, Sheet Harbour, abundance series is the longest elver series available for the species. Annual recruitment varied without trend from 0.1 to 0.5 million elvers between 1989 and 1999 (Figure 16; Jessop 2003a). In the East River, Chester, the total run of elvers peaked at 1.7 million in 2002. Since the overlap periods of the two series are strongly correlated, a combined index of 13 years can be interpreted. Elver recruitment showed inter-annual variability but no indication of decline between 1989 and 2002.
In 1989, the first two licences were issued to fish experimentally for American eel elvers in the lower reaches of rivers draining into the Bay of Fundy in Nova Scotia and New Brunswick. In 1996, seven commercial licences were issued (Jessop 1998b). Within a geographic region, the elver catch depends on elver abundance, fishing effort, and elver catchability (availability, fishing efficiency depending on gear types) and the distribution of elvers through the run. Elver CPUE (kg caught per hour fished) rose from 1996 to peak in 2000, and subsequently declined (Figure 16).
Figure 16. (A) Elver counts in two Nova Scotian rivers (from R. Bradford, DFO): East River, Sheet Harbour (1989-1999) and East River, Chester (1996-2002); (B) CPUE from commercial elver licences (1996-2005, 2005 being incomplete).
Indices of Juvenile Abundance
The longest fisheries-independent abundance indicators for the American eel come from electrofishing surveys for salmonids conducted in the Restigouche, Miramichi and Margaree rivers in the Maritime Provinces. Surveys were conducted in sites closed by barrier nets and open unbarriered sites. Densities were estimated by the depletion method where possible, or by mean ratios of counts to total populations derived from sites where the depletion method was applied. Densities in recent years are generally below the long-term mean. Mean densities (eels per 100 m-2) in the Restigouche River peaked in 2001 and 2002, but densities recorded in previous and subsequent years were below the long-term mean (Figure 17; Cairns et al., submitted). In the Miramichi River, eel densities varied irregularly in the 1950s and 1960s, peaked in the early 1970s, and then declined to a minimum by the late 1980s. Densities have since shown a modest recovery but remain well below the long-term mean (Cairns et al. submitted). Eel densities measured by electrofishing in the Miramichi River (Figure 17) show similar trends to landings in the southern Gulf of St. Lawrence since the 1970s (Figure 18). Densities in the Margaree River peaked in the early 1960s, showed a lesser peak in the 1970s and subsequently declined to very low levels (Figure 17).
Figure 17. Mean number of eels (± SE) per 100 m² in three rivers in the southern Gulf of St. Lawrence, estimated from electrofishing surveys (from D.K. Cairns, DFO): (A) Restigouche River (1972-2003); (B) Miramichi River (1952-2003); (C) Margaree River (1957-2003).
Figure 18. Reported landings in tonnes of American eels in Ontario (Casselman 2003, updated by J.M. Casselman, OMNR), Quebec (Caron et al., submitted), Southern Gulf of St. Lawrence (D.K. Cairns, DFO), Scotia‑Fundy (R. Bradford, DFO), Newfoundland (M. O’Connell, DFO), Canada, and North America. Many factors affect landings; for specific explanations, see original sources.
Electrofishing indices are available for several rivers in the Scotia-Fundy region (Figure 19). The Hammond, Kennebecasis, Nashwaak and Keswick rivers are located in the lower Saint John River watershed (Figure 15). Most early surveys were done with barriered (closed) sites and most recent surveys were done at open sites. Results obtained from these two methods cannot be directly compared. Results may also have been affected by inconsistent reporting of eel bycatch. In general, there are no consistent temporal trends within a single method (barrier or open) in New Brunswick sites. In the three Nova Scotia sites, the electrofishing series has declined since the late 1990s.
Figure 19. Arithmetic annual mean ( ± standard error) of American eels per 100 m2in the first sweep of electrofishing surveys in barriered and open sites in New Brunswick and Nova Scotia rivers that flow into the Bay of Fundy and the Atlantic Ocean.
Indices of Yellow Eel Abundance
Most eels harvested in the Maritime Provinces are yellow eels. The only commercial fishery allowed on Prince Edward Island is a fyke net fishery. A logbook program that has operated since 1996 gathers information on effort and landings. Three to seven commercial eel fishers volunteer each year to participate in the program. For each day of the fishing season, number of fyke nets in the water, total catch of sublegal (under 50.8 cm; mean age 4.9 ± 1.2 years) and legal eels are recorded (D.K. Cairns, DFO, pers. obs.).
CPUE of sublegal eels peaked in 1999, declined, and has since risen, whereas CPUE of legal sized eels in the Prince Edward Island fyke net fishery has increased between 1996 and 2004 (Figure 20). The rise in CPUE corresponds to recent rising trends in reported landings in Gulf New Brunswick and Prince Edward Island (Figure 18).
Figure 20. CPUE of: (A) sublegal; and (B) legal American eels by commercial fyke net fishers on Prince Edward Island (1996-2004; from D.K. Cairns, DFO).
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