The American eel is an important part of the diversity of life in Lake Ontario and a valuable indicator of the health of the ecosystem. As a top predator, eels help to keep other fish species in balance, including invasive species such as the goby.
The formerly abundant American eel has a long history as a food and commercial product for residents of the upper St. Lawrence River and Lake Ontario. Eels were a highly valued fish resource for Aboriginal people, particularly the St. Lawrence Iroquois, who depended upon them as winter and travelling food. Historical accounts from the mid-1600s record a fisherman spearing as many as 1,000 eel in a single night.
Records of commercial fisheries list catches of eel as early as 1886. During the 1980s and early 1990s, the American eel was one of the top three species in commercial value to Ontario's fishing industry. At its peak, the eel harvest was valued at $600,000 and, in some years, eel accounted for almost half of the value of the entire commercial fish harvest from Lake Ontario.
|Figure 1. Average number of eels ascending the eel ladder per day, over a 31-day period for each year from 1974 to 2004. The ladder is located at the R.H. Saunders Hydroelectric Dam, in Cornwall, Ontario. Note: no data are available for 1996.|
Over recent decades, the number of young American eels entering the upper St. Lawrence River and Lake Ontario has been declining dramatically (Figure 1). For example, the average number of eels migrating up the St. Lawrence River near Cornwall decreased from 25,000 per day in the 1980s to roughly 230 per day in 2005. American eel appears to be in decline throughout its global range.
At the same time, the commercial catch of eel has declined from approximately 223,000 kilograms (kg) in the early 1980s to 11,000 kg in 2002.
Distribution and Life Cycle of the American Eel
|Figure 2. Global distribution of American eel. (Fisheries and Oceans Canada, American Eel, Underwater World. (Reproduced with the permission of Her Majesty the Queen in Right of Canada, 2006)|
Globally, American eel are found in coastal freshwater and marine waters stretching from Greenland along the east coast of North America to northern South America (Figure 2). Eels extend into Ontario through the St. Lawrence River and Lake Ontario.
American eels have a complex life cycle (Figure 3). All American eel are part of a single breeding population that spawns in only one place in the world – the Sargasso Sea in the Atlantic Ocean. From there, young eels drift with ocean currents and then migrate inland into streams, rivers and lakes. This journey may take many years to complete with some eels travelling as far as 6,000 kilometres. After reaching these freshwater bodies they feed and mature for approximately 10 to 25 years before migrating back to the Sargasso Sea to spawn.
|Figure 3. The life cycle of the American eel involves several stages. It begins in the ocean when the eel larva, called the leptocephalus, hatches from the egg. The leptocephalus, carried in the Gulf Stream, changes into a glass eel (a more elongated, eel-like shape) near the coast and migrates inland into streams, rivers, and lakes to grow and evolve into the elver (a small version of the adult eel). In fresh water, the elver grows into the larger yellow eel and then finally into the silver eel (almost full-grown). The silver eel then migrates back to the Sargasso Sea and spawns, thereby beginning the cycle once again. (created by Rob Slapkauskas)|
Virtually all American eels in Ontario are large, highly fecund (egg-laden) females. Prior to the decline of eel in Ontario, eels in Lake Ontario and the upper St. Lawrence River appear to have contributed substantially to reproduction of the global eel population.
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