The extinction of Wild Salmon in the river Rhine
zondag, december 19, 2010 · Category Environment · comments 1
The salmon fisheries in the Dutch rivers reached a peak at the end of the 19th century. In the 19th century, salmon were so plentiful in the Rhine that they were used to feed the poor. Since 1957, salmon has completely disappeared in the Dutch fresh waters.
Salmon; a grand, king fish
Salmon can grow very large: to a maximum of 1.5 meters long. They eat herring, smelt and crustaceans. They spend their first year of life in fresh water, after which they migrate to sea. After travelling for one to three years, they return to their place of birth to spawn.
First attemps for reintroduction
In 1985 an attempt was made to maintain an artificial salmon population in the Rhine. 4000 1-year olds were released with the intention to repeat this every year up through 1990, resulting in 20,000 animals. Due to a poison disaster, when a large quantity of chemicals was discharged into the Rhine following an accident at a Swiss company in Basal and fruitless attempts to retain the pollution, the project did not succeed.
Water quality in the river Rhine
The Rhine's water quality has been a major point of concern since the 50s. Halfway through the 60s life had all but disappeared from the river, which had been a paradise for fish up till the beginning of the 20th century. The decline was caused by the unchecked discharge of industrial waste and water.
Pressured by environmental groups, in the 1960's the International Commission for the Protection of the Rhine (60 years) was founded by the four countries through which the Rhine flows: Switzerland, Germany, France and the Netherlands.
Further improvements in the 1990's and 21st century
Since then the situation has improved so much - in part because salt dumping by French potassium mines has been curtailed. Germany and Switzerland have invested mainly in fish ladders to eliminate the Salmons biggest enemy: dams and hydropower installations along the migration route. With the now clean water salmon has been reintroduced to the river Rhine.
Will the salmon return?
Some biologists doubt whether the salmon will return; entrance to the rivers is closed by the Delta Works and the Afsluitdijk, to name a few, and there are too many flood-control dams and locks along the river to easily reach the spawning grounds. In addition, the temperature of the rivers such as the Rhine has risen by around 6 degrees Centigrade, whereby the water contains less oxygen which is necessary for burning off fat reserves.
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