Rybí restaurace Šupina a Šupinka, apartmány

Eel

Drawing © Radek Doško

  • Latin name: Anguilla anguilla
  • Slovak: Úhor obyčajný
  • English: Eel
  • German: Aal, Flussaal
  • sort: Anguilliformes
  • family: Anguillidae
  • feed: omnivore, predator
  • life span: 20 years
  • sexual maturity: 10-15 years
  • reproduction:
  • common size: 50-80 cm
  • maximum: up to 150 cm

The eel is entirely unmistakable fish residing in waters in a great part of Europe.  It is famous for its unique reproduction cycle during which mature eel migrate downstream heading to the Sargasso Sea in the Atlantic and the resultant larvae drift towards the coast of Europe where its parents grew up through difficult and distressful way.

However, only females enter freshwater, the males remain in estuaries or in the sea.   Only just a few males were found in our country during researches, virtually, all our eels are females.

The impenetrability of rivers (weirs, dams) is the problem for the migrating fish therefore the survival of the fish is ensured only by artificial stocking in many places and thus the eel can be found at places where it was not indigenous (the possibility to return the adult fish into the breeding ground is not being dealt with).

The stocking rate is decreasing at other places because expensive stocking does not sufficiently compensate for the original rich stock of young specimens migrating naturally.

Due to a great interest in commercial farming of the eel, there are a lot of eel farms using a great part of the caught eel stock (monté) and thus increasing their price on the market, however, not contributing to the reproduction of this species in any way.

The way back to the sea is not easy for the mature eel, too; lots of them die broken into pieces by the turbines of hydro power plants and especially the eels from South Bohemia that have to swim through lots of reservoirs on their way down the Vltava river do not have any chance to finish migrating for reproduction successfully in fact.

The eel is a carnivorous, bottom dwelling fish being active mainly at night. It is unbelievably voracious and movable, it can dig itself deeply in the bottom and move under the surface of sullage, it is very resistant while it stays ashore for a short period of time and it is able to overcome various sorts of obstacles.

Its body has perfectly adapted during its development – it has elongated into a serpentine shape and got rid of everything useless.  The scales turned into small lined formations imbedded deeply in the strong skin covered with an immense layer of slimy secretion, ventral fins disappeared and dorsal and anal fins grew together and confluent with caudal fin form one unique fin from the anus to the middle of the back.

The head of the eel is small and elongated, with the large mouth and gills fully covered with a skinny lap protecting them from excessive mud penetration.  The tough eel skin creates a great amount of slimy secretion and provides the eel with a double protection. Moreover, it is interwoven with a rich network of capillaries and it is a complementary respirator organ ensuring the eel with up to 85% of oxygen coverage (probably the coverage in resting state).    Thanks to the adaptation, the eel can make it with a relatively small surface of gills that are really surprisingly small with respect to its size.

There are two morphologic strains in our waters – narrow and broad headed. The broad headed type features robust cylindrical body and significantly broader head, of course. It feeds mainly on bigger pieces and when it grows older it becomes purely carnivorous. The narrow headed type is more subtle and slim and it feeds rather on water invertebrates as its jaws are narrower.

The interesting thing is the eel’s blood contains a substance which is highly toxic for mammals mainly.  A smaller dog died within four minutes when only a half gram of eel’s blood serum had been injected under its skin in laboratories  (otter managed to survive – the reason might be that the poison is decomposed by digestive juices quite quickly).

The effect of the poisoning resembles venom poisoning and thus it should not be underestimated. If an eye is contaminated with a drop of the eel’s blood, it is very unpleasant and painful and the blood should not get into an open wound.  Because this poison is of protein character, it is thermally unstable and decomposes already at temperatures of around 60°C.  Therefore cooked eel meat is entirely harmless; on contrary, it is evaluated as one of the best fish meat at all.

You can find more information at www.mrk.cz Section ‘Fish Encyclopaedia’.