The Demise of American Eel in the Upper St
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American Fisheries Society Symposium 78:149–188, 2015 © 2015 by the American Fisheries Society The Demise of American Eel in the Upper St. Lawrence River, Lake Ontario, Ottawa River and Associated Watersheds: Implications of Regional Cumulative Effects in Ontario ROB MACGREGOR* Ontario Ministry of Natural Resources (retired) RR #1, Box 8455, Peterborough, Ontario K9J 6X2, Canada TIM HAXTON Ontario Ministry of Natural Resources 300 Water Street - 4th Floor South, Peterborough, Ontario K9J 8M5, Canada LORNE GREIG ESSA Technologies Ltd. 77 Angelica Ave., Richmond Hill, Ontario L4S 2C9, Canada JOHN M. CASSElmAN Queens University Biosciences Complex, 116 Barrie Street, Kingston, Ontario K7L 3N6, Canada JOHN M. DEttmERS Great Lakes Fishery Commission 2100 Commonwealth Boulevard, Ste 100, Ann Arbor, Michigan 4810, USA WIllIAM A. AllEN Heritage One 9 First Avenue, Burk’s Falls, Ontario P0A 1C0, Canada DAVID G. OLIVER Skylark Information Systems Ltd. 3444 Rexway Drive, Burlington, Ontario L7N 2L6, Canada LArrY MCDErmOtt Shabot Obadjiwan First Nation-Ambassador and Plenty Canada 266 Plenty Lane, RR #3, Lanark, Ontario K0G 1K0, Canada *Corresponding author: [email protected] 149 150 MacGregor et al. Abstract.—American Eel mortality has increased substantially over the past century due largely to significant cumulative effects of fishing and fish passage through hydro-electric turbines across their range. Nowhere has this been more pronounced than in waters of the St. Lawrence River, Lake Ontario, Ottawa River and associated water- sheds. We illustrate this by examining the cumulative effects of hydro- electric facilities on eels migrating downstream through the Mississippi River and Ottawa River, and outline further impacts eels encounter en route to spawn in the Sargasso Sea. The probability of a mature female eel surviving its emigration through the Mississippi and Ottawa River to the upper St. Lawrence River is estimated to be as low as 2.8% due to turbine mortalities alone (2.8–40%). Mortality risk increases as the eel attempts to run the gauntlet of fisheries in the lower St. Lawrence River and the probability of out-migration survival is estimated to be as low as 1.4%. Some mortalities could be mitigated through improved appli- cation of existing laws, development of policy requiring consideration of cumulative effects and improved integration among program ar- eas responsible for sustainable management of fisheries, biodiversity, dams and hydro-electric facilities. We recommend changes to policy, procedures and internal organizational structures provided with clear directions, and call for increased accommodation of Aboriginal per- spectives. Introduction cies Act is currently under review (USFWS 2012a) based on a 90-d finding that American The American Eel Anguilla rostrata, Eel may merit protection under the Endan- which was formerly abundant and widely gered Species Act (USFWS 2012b, 2012c). distributed across eastern North America This unique species is composed of one has declined dramatically in some regions, single spawning stock, with a contingent particularly at the extremity of their range life history strategy that in the past has been in the upper St. Lawrence River and Lake highly successful in a variety of habitats Ontario (USLR-LO) (Casselman 2003), Ot- across North America (Helfman et al. 1987; tawa River and associated inland watersheds Daverat et al. 2006; Secor 2010). However, (MacGregor et al. 2009). The species is listed its panmictic, migratory nature has left the as endangered under Ontario’s Endangered species exposed to mounting anthropogenic Species Act (Ontario Government 2007). impacts that continue to accumulate across a The Committee on the Status of Endangered wide geographic range. The effects are most Wildlife in Canada (COSEWIC) recently dramatic in the USLR-LO and associated wa- upgraded its recommended national desig- tersheds (including the Ottawa River), where nation from Special Concern to Threatened an especially important segment of the spe- across Canada (COSEWIC 2012). The status cies continues to persist near the extremity of of American Eel within the authority of the its historic range, albeit at rapidly declining Atlantic States Marine Fisheries Commis- abundance levels (Casselman 2003; Mac- sion (ASFMC) has recent been declared de- Gregor et al. 2008, 2009, 2010, 2011) and pleted (ASFMC 2012). The national status of exhibiting pronounced range contractions the species under the U. S. Endangered Spe- (MacGregor et al. 2009, 2010, 2011). Cumulative Effects on American Eel 151 Eels in the USLR-LO appear to com- farther north, which, discharging their prise a distinct segment of the North Ameri- waters here, makes us a present of this can population; when mature, eels from the manna that nourishes us…” (Thwaites USLR-LO and associated watersheds are 1896–1901: 6: 311). comprised exclusively of large old females exhibiting high fecundity (Casselman 2003; These observations were confirmed al- COSEWIC 2006; Tremblay 2009; Bernat- most four centuries later by Verreault and chez et al. 2011). Observed declines of this Dumont (2003) when they estimated that eels important subpopulation of the North Ameri- produced in the USLR-LO and associated can eel population may have far-reaching watersheds still accounted for some 67% of implications for the fecundity of the species, the catch in the large Quebec silver eel fish- its resilience to future environmental pertur- ery. The proportion has remained high but is bations and anthropogenic mortality, and its declining (Verreault and Dumont 2003) as ability to re-inhabit the St. Lawrence River the abundance of eels in these waters has col- and watersheds of Lake Ontario and the Ot- lapsed (Casselman 2003; MacGregor et al. tawa River (Casselman 2003; Verreault and 2008, 2009, 2010, 2011). Dumont 2003; MacGregor et al. 2009, 2010; Moreover, the apparently large numbers Venturelli et al. 2010; Bernatchez et al. 2011). of downstream migrating eels each autumn This segment of the population of American from the St. Lawrence River (en route to the Eel is comprised of reproductively valuable Sargasso Sea) supported what had once been individuals (all large females, the most fecund described as the most productive eel fishery in the species’ range), meriting strong protec- in the world (New York Times 1880), hav- tion and recovery actions. At former levels of ing long and important cultural, natural heri- abundance, eels naturally produced in these tage and economic values in eastern Canada waters must have contributed substantially to (MacGregor et al. 2009). Some of the weir species-level fecundity and spawner output fisheries for eels in Quebec had been in the (Casselman 2003; COSEWIC 2006; Trem- same family at the same location for 150 blay 2009; CSAS 2011). years. Eels have been important in these waters Descriptions of population-level trends for centuries. A Jesuit Relation of 1634 noted in American Eel across North America have that the important eel fisheries near Quebec noted its historically wide distribution, high City on the St. Lawrence River were supplied abundance and importance of the species to to a large extent by eels produced upstream in Indigenous peoples and early European set- present-day Ontario and New York (i.e., Lake tlers in eastern North America (Casselman Ontario and other important watersheds such 2003; Prosper and Paulette 2003; MacGregor as the Ottawa River, in Canada, and Oneida et al. 2009; McDermott and Wilson 2010; River in the United States): Denny et al. 2012). Together with possible shifts in oceanic conditions (Freidland et al. “It is wonderful how many of these fish 2007; Bonhommeau et al. 2008; Casselman, are found in this great river, in the months unpublished data), cumulative anthropogenic of September and October, and this im- effects arising from the loss of formerly ac- mediately in front of the settlement of cessible habitat and mortalities due to fishing our French…” and hydro-electric turbines contributed to a 99.6% decline in recruitment to the USLR- “It is thought that this great abundance LO and associated watersheds (e.g., Ottawa is supplied by some lakes in the country River) (Casselman 2003; Verreault et al. 152 MacGregor et al. 2003; MacGregor et al. 2009). Since the on- 2012). Losses of species such as American set of the silver eel decline preceded the ma- Eel not only represent significant lost eco- jor decline in recruitment in the mid-1980s, logical, biodiversity, natural heritage and it appears that the decline in spawning stock economic benefits due to cumulative effects. size was not due to poor recruitment. Rather, They also threaten Aboriginal rights (Tollef- it was due to large-scale mortality factors as- son and Wipond 1998) and reflect lack of sociated with high exploitation in upstream respect for Ginawaydaganuk: a principle of Lake Ontario and to construction of hydro- Algonquin law that acknowledges the web power dams in the late 1950s (de Lafontaine of life or the interconnectedness of all things et al. 2009a). (McDermott and Wilson 2010). Eels from the USLR-LO (the last strong- In September 2009, a large American hold for the species in Ontario) collapsed by Eel (1.1 m) was captured during routine as- the mid-1980s (Casselman 2003; MacGregor sessment netting in Mississippi Lake, on the et al. 2008, 2009), some 30 years after the Mississippi River, a tributary of the Ottawa construction of the large Moses-Saunders River (Figure 1). The Ottawa River water- hydro-electric facility across the St. Law- shed is large, encompassing a drainage area rence River. However, significant declines of 146,000 km2, representing about 12% of associated with hydro-electric facilities the St. Lawrence drainage area, including began at a much earlier time in inland wa- hundreds of lakes in Ontario and Québec. An tersheds of Ontario where the duration of estimated 3,700 km2 of suitable habitat was impact has been much longer, often accu- present within this system before extensive mulating over a century (MacGregor et al. dam construction throughout the watershed 2010, 2011).