This video from Denmark says about itself:
Denmark’s AQUA is the largest freshwater aquarium in Europe. It’s unique galleries include artificial lakes with side viewing glasses, which simulate typical lake ecosystems in Denmark.
This video serves as a guide of common European freshwater fish species that are found at AQUA. Four different environments are featured, including a polluted lake, a healthy lake, a typical Danish stream and the night environment.
From National Geographic News:
57 New Freshwater Fish Species Found in Europe
November 14, 2007
Europe’s rivers and lakes boast at least 57 more freshwater fish species than previously thought, scientists have announced.
The new species were discovered during a seven-year assessment of the conservation status of freshwater fish in Europe that was conducted in collaboration with the World Conservation Union (IUCN).
The findings lengthen Europe’s list of freshwater fish to 522 species.
And the study authors say many more undescribed fish have been found or are suspected to exist, potentially taking the total number of confirmed species to 600 or higher.
“The new species come from all over” Europe, said co-author Jörg Freyhof of the Leibniz Institute of Freshwater Ecology and Inland Fisheries in Berlin, Germany.
Freyhof and co-author Maurice Kottelat from Cornol, Switzerland, present their data in the Handbook of European Freshwater Fishes.
Data from the handbook, which was released in early November, also determined that more than a third of Europe’s 522 freshwater fish species are at risk of extinction and that 12 species are already extinct.
The newly described species include the world’s smallest known cisco—a type of whitefish—that was found in Germany’s Lake Stechlin, north of Berlin.
The silvery pink fish, dubbed Coregonus fontanae, was found to be distinct from a much larger cisco species from the same lake.
Two new species of troutlike char were discovered in alpine lakes in Germany and Switzerland.
The study team also named eight new sculpin, a type of small, squat river fish often found under stones.
One of these freshly named species, Cottus perifretum, had been labeled as another European sculpin, Cottus gobio.
Yet the two species are relatively easy to tell apart, according to Freyhof.
“The skin of Cottus gobio is very smooth, but perifretum’s is like sandpaper,” he said.
“There are many molecular markers which also distinguish the two species.”
Harder to tell apart were members of a group of lake fish from Central and Eastern Europe called shemayas. But the study team was able to identify four new shemaya species.
“At first glance they appear like herrings—you really have to look at them in detail,” Freyhof said. …
According to Freyhof, the new freshwater species might have remained undiscovered for so long because until now scientists had not compared fish closely enough across countries’ boundaries.
For example, a newly discovered species of chub from Greece was long thought to be the same species as a chub living in Britain.
But the Grecian fish has black fins, while the British variety has orange fins.
“This color fades when the fish are preserved, so maybe a Greek scientist had seen a [British museum specimen] and so couldn’t see it didn’t have black fins,” Freyhof said.
The new Greek fish, called Squalius orpheus, is one of five previously unrecognized chub species identified by researchers during their search.
Fish species in North European prehistory: here.