The Toronto Star ran an excellent story about efforts to restore the American Eel to Lake Ontario. Here's an excerpt:
Officials examining effectiveness of water restocking program
Mary McNiven places a dead eel in a blender at her Charlottetown lab, puts the lid on and presses a button. The result is an eel“smoothie” that is helping Ontario officials determine if their efforts at bringing back the elusive American eel to Ontario waters via a restocking program is working. McNiven, a professor of animal sciences at the Atlantic Veterinary College in P.E.I, describes eels as a “mystic” species. They are mysterious even for those who study them, and that is making the effort to boost their numbers in Ontario a complicated task.
“For a researcher,” says McNiven, that’s “the fun thing — that there’s so much not known.” American eels, long, slippery, snakelike fish, were once a lucrative product for Ontario fishermen, but fewer of them are making their way to the province, where fishing of the species was banned in 2004. American eels are now listed as an endangered species in Ontario. The relatively few eels that make it to Ontario now come from the Sargasso Sea in the mid-North Atlantic Ocean, the only place in the world where the species spawns. It is not clear what is causing the fish to struggle in Ontario, but some factors could include physical barriers, like hydro dams and turbines at hydroelectric facilities.
Other reasons could include warmer water temperatures and deteriorating water quality. Ontario Power Generation understands it may be playing a part in the eel’s decline, so it, along with Ontario Ministry of Natural Resources and the Federal Department of Fisheries and Oceans, bought eels from fishermen in Nova Scotia, where the fish is still plentiful and a commercial fishery continues. More than four million eels were driven to Ontario from Nova Scotia between 2006 and 2010. They were dropped in waterways in the areas of Thousand Islands, east of Kingston, and the Bay of Quinte, near Belleville. These stocked eels have had a tiny mark made on a bone in their ears, so that they can be told apart from their non-stocked counterparts. McNiven says it’s important the transported eels make the trip quickly because of the need for females for spawning purposes.Young eels don’t have a fixed sex and she says their gender is determined by several factors, one being the proximity of other eels: when eels are surrounded by other eelsthey have a greater chance of becoming male; when they swim apart from each other they have a greater chance of becoming female. The sooner the eels arrive in Ontario, the sooner they can be separated and transform into females. “Sperm is a dime a dozen, but the eggs are the thing that are in short supply. So we want those,” McNiven says.
Ron Threader, a senior environmental adviser with OPG, says Quebec commercial fishermen told authorities about finding smallereels in their catch in 2010. OPG is now buying eels from fishermen on the St. Lawrence River in Quebec, where they are being caught, presumably on their way back to the Sargasso Sea from Ontario. Both stocked and non-stocked eels are being caught to evaluate the effectiveness of the restocking program.
There are questions about whether the program is working, because some of the stocked eelsbeing caught in the St. Lawrence are younger and smaller than the nonstocked. Eels don’t eat at all when they become sexually mature, and therefore don’t consume anything on their way from Ontario to spawn in the mid-Atlantic. Their bodies then begin to consume parts of themselves, such as the digestive tract, to use whatever nutrients are available.
“They’re kind of burning up whatever part of their body they aren’t using anymore,” says McNiven.
If the eels are too small — and therefore have less energy — there are concerns they will not have enough fat, nutrients and energy to make the long trip and procreate afterwards.
“We want to see if there is, in fact, a difference between these fish and their larger sisters,” says Threader.
That is where McNiven and her blender come in. She is liquefying both stocked and non-stocked eels to “see whether or not their body composition is equivalent” in nutritional content and energy output.
Threader says the fact the restocked fish are smaller is “not necessarily a bad thing,” because they are a similar size to Nova Scotia eels when they leave for the Sargasso.
It is possible the eels are not yet heading to the Sargasso Sea and instead are hanging out in the Maritimes for a few years, continuing to eat. It is also possible that the restocked eels being caught in the St. Lawrence are just a few stragglers, and the majority could still be in the ecosystem in Ontario.
After the eels are ground up, samples of the liquefied eels are put into laboratory containers for testing.
After multiple years of data from McNiven’s lab are collected and combined with Threader’s data, it should be possible to find out if the restocking program is working. Threader says the jury is still out. “My guess is another two years we’ll have a pretty good handle on what’s happening.”
See Original Article here.