It was an unlucky Friday the 13th for small fishin the St. Lawrence after 50,000 predatory eels were set freein thewaters around the Thousand Islands.

The young American eels were released into the St. Lawrence River near the islands on Thursday as part of a multi-year projectto helprestore the eelpopulation in Ontario waterways,the Ontario Ministry of Natural Resources said in a news release Friday.

Eels are a valuable part of the ecosystem, said Natural Resources Minister David Ramsay. Their preyincludes invasive species such as gobies, bottom-dwelling fish from Europeintroduced to Ontario in recent decades. Theynow threaten bottom fish that are native to theprovince.

Theonce abundant eel has grown so rare in the past decade that in 2004, the Ontario government banned commercial eel fishing in Lake Ontario and the upper St. Lawrence River, and banned sport fishing of eels provincewide.

Hydroelectric dams interfered with population

Both Canada and the U.S. are now considering listing the eel as an endangered species.

This year, Ontario Power Generation bought the 50,000 eels to stock the St. Lawrence River as part of a joint project with the Ontario Ministry of Natural Resources, the Ontario Federation of Anglers and Hunters and the Ontario Commercial Fisheries Association.

According to the Natural Resources Ministry, hydroelectric dams helped cause a dramatic decline in the eel population by blocking the migration routesthe fish use in their journey between the Great Lakes and the Sargasso Sea. Researchers believe that is where the fish spawn.

Commercial fishing has also taken a toll on the eel population.

An eel ladder installed at the R.H. Saunders Hydroelectric Dam in Cornwall in 1974 to aid the migration of eels upstream has seen the number of fish fall from more than one million a year in the early 1980s to fewer than 3,500 annually.