For a long time it was believed, that eels originate from the sludge of reedy marshes on the banks and coasts of rivers and seas, since the arrivals of young eel in the spring each year occurred so spontaneously in the lower river reaches. Spawning areas remained unknown until the end of the 19th century and not before 20th century it became known that the eel migrate for reproduction from the rivers into the Sargasso Sea, an area in the West-Atlantic ocean. Small eel larvae, also called leptocephalus due to the form of their head, migrate from there after ca. 2 years to the European coasts, drifted by strong North-Atlantic ocean currents. As they reach the land, their bodies change the form, turning them at first into glass eels, and later into elvers. As they reach the approximate size of a pencil, the animals migrate in great shoals the rivers upwards. In the 1950’s, the ship lock keepers in Bremen opened the sluice gates extra at night, in order to allow for the elver shoal, often over a 1-2m wide and up to 100m long, to ascend into the Weser. They grow within the next years in rivers and streams to the animals called the big "yellow eel". At the end of this time the eels migrate the river downwards, triggered by the water levels which rise in the autumn, back to the marine spawning areas. At this point of time, they have reached the development stage of the silver eel.

Enormous abundance of eel population is a result of the centuries-long river fishery tradition. Well smoked eel is considered to be delicacy, and preferred fish species among sport fishermen. The eel population had however dramatically dropped over the last 10 years, especially in regard to the glass eel ascent. Today, the eel populations in Weser and Werra sustain only thanks to the stemming of fisheries. A natural ascent does not exist in Werra at the time. The causes of such deterioration are multiple and involve all life stages, which means that a successful protection must comprise all age phases. It is therefore necessary to restore the functional continuity of Werra, Weser and other rivers, especially in respect of successful eel descent. European eel was the fish of the year 2009.

Foto: Schwevers (2002)