The eel (Anguilla anguila) is one of the most mysterious species living in Finnish water ecosystems. It is also an endangered species.

The living habits of eels are mostly unknown. Eels live in freshwater environments such as lakes and rivers. They are predators that use other fish and crabs as their food.

The eel is a migratory fish. When it has grown into an adult, it embarks on a spawning migration. It travels through rivers in order to end up in the sea. Once in the sea, it begins its long migration. Based on modern research, eels have been discovered to migrate to the Sargasso Sea on other side of the Atlantic. This is where the species is thought to reproduce.

The young eel larvae develop in the Sargasso Sea and move towards Europe with the help of the Gulf stream. Finally, the larvae develop into so-called glass eels, which travel inland through rivers. These glass eels grow and gradually develop into adult eels. 

Eels are a long-lived species. They can live in lakes and rivers for decades before embarking on their spawning migration. 

Hydroelectric power plants provide the greatest threat to eels as a species. Dams block the waterways that eels need to use to reach the sea during their migration. In addition to this, there are no restrictions on eel fishing in Finland. As a result of this, eel populations are rapidly decreasing.

Protecting eels is difficult, because it requires changes in the hydroelectric power plants that block their migration routes. Power plants should build "fish roads", through which migratory fish can bypass the power plant safely. Restricting eel fishing is another challenge. Although eels are extremely endangered, they are considered a popular food in many European countries. As a result, eels are fished in great quantities despite their endangered status.

An eel has been caught in Italy.