Which large lake has the least functioning fish population and why?

 Welcome to Darwin’s Nightmare

Lake Victoria is the largest lake in Africa and the third largest in the world. It’s one of the sources of the Nile River, which flows all year thanks to this natural reservoir, even though it runs through a desert. It has four native names because a lot of people live near it.

And for millennia, it hosted the largest variety of freshwater fish in the world, nearly a thousand different species. Most of these are in a family called “cichlids” which are fish about the size of your hand.

For centuries, fishers around the lake would go out in their small boats and reap the bounty of the lake. I mean, there’s not a lot of meat on them, but they’re perfectly edible and they’re small enough to be dried in the abundant sunshine of the region. That meant one good catch could last you for weeks or months.

But in the 1950s, some not too bright people thought it would be more fun to introduce a species that would be more fun for leisure fisherman, hoping to bring tourists to the lake. The one they introduced was the Nile Perch.

The Nile Perch can grow to be the size of a small child. Guess what it eats? That’s right! Smaller fish. Unlike its native river, Lake Victoria was an all-you-can-eat buffet.

By the 1970s the Nile Perch was being fished commercially, but not in the little boats used by the people who lived there. No, a Nile Perch could overturn a little boat, so fishers came in big boats. Meanwhile, over 500 species of cichlid in the lake went extinct and the number of fish in the surviving species declined sharply, so much so that few live to become large enough to breed. It would hardly matter now because the Nile Perch can’t find cichlids either anymore so it eats shrimp and minnows.

Also, Nile Perch are so fatty that if you tried to sun dry them they would spoil before they dry, so they have to be smoked - in a region where forests are already under tremendous human pressure. This is so expensive that people who live near the lake can’t afford them, so every day the catch is flown to Europe for sale.

The good news is the lake is so barren of fish that it’s likely the Nile Perch population is going to collapse from starvation one of these days. The bad news is that pretty much all the fish will be gone well before that happened.

Oh, and the award winning 2004 documentary about this is, of course “Darwin’s Nightmare”. You can find a few foreign subtitled versions on YouTube or hunt down the title. I can’t recommend it very highly as it’s mostly just interviews with no narration, but it is what it is.

Which lake occupies the most unique position in the natural world?

 Lake Itomori, which appeared as a meteorite lake in "Your Name."

What if such a meteorite lake actually existed?

Yes, they exist.

In the New Quebec Crater on Canada's Ungava Peninsula, there is a meteorite lake called Lake Pingaluit.

The name comes from the Inuit word "pingalui," which means "acne."

While any meteorite lake is rare, this lake is considered to have the most beautiful shape of any meteorite lake in the world. Since the release of the movie "Your Name," this lake has become famous for its unique form.

In fact, this lake also holds a special title: it is "one of the clearest lakes in the world ." And for good reason. This lake is actually located about 100 meters above the elevation of the land where the crater is situated. As a result, there are no inflowing rivers, and the water is stored from snow and rain, with few soil particles, so you can see up to 35 meters below with the naked eye.

This crater lake is 3.44 km in diameter and 267 m deep. The meteorite eroded about 100 m of the ground where the crater is located, creating a plateau over 100 m high around the crater. The photo below shows a diagram illustrating the height of the New Quebec Crater.

Water occupies about 70-80% of this depression, making it one of the deepest lakes in North America. With a salinity of less than 3 ppm (compared to 500 ppm in the Great Lakes), it is one of the world's purest freshwater lakes, possessing a unique and precious water quality.

The crater and its surroundings are part of Pingaluit National Park in Canada, which was formed in 2004. Why not see with your own eyes this precious place where Earth's history changed?

How deep is the world's deepest lake?

 Lake Baikal (5,315 feet [1,620 meters])

Lake Baikal, in Siberia, holds the distinction of being both the deepest lake in the world and the largest freshwater lake, holding more than 20% of the unfrozen fresh water on the surface of Earth.

Lake Baikal is the largest freshwater lake in the world (by volume) and the world's deepest lake. Somewhat crescent-shaped, it is in the southern Siberia area of Russia.

Lake Baikal is so deep because it is located in an active continental rift zone. The rift zone is widening at a rate of about 1 inch (2.5 cm) per year. As the rift grows wider, it also grows deeper through subsidence. So, Lake Baikal could grow wider and deeper in the future.