A Medieval Water Power Brought Down Salmon Stocks
The large declines of salmon stocks were identified in North-Western Europe. For a long time, ecologists blamed water contamination and over-fishing that happened in and after the 19th century for the decrease of salmon in water bodies.
However, later study and investigation have proved that the water power that was initiated during the medieval times before the 19th century is a primary cause for the decrease in salmons. With the setting up of water power, the gravel beds in rivers and streams have been slowly destructed making it difficult for salmons to swim upstream and lay their eggs, causing a huge decline in the salmon stocks.
Salmon decrease has been ascribed to the fish spawning which has clearly been affected by power plants. Taking quick measures to fix these areas might not help because the gravel beds have already been disturbed and it will take ages for fish stocks to come back to its natural form.
Study has found that the construction of water mills have greatly affected the salmons. This is because water mills require the construction of dams which eventually affected the salmons spawning. The gravel beds meant for salmons to lay eggs were covered with sand and silt.
Roel Lauwerier from the Cultural Heritage Agency of the Netherlands said that, "The Middle Ages shows a sudden change in terms of proportions: the number of locations at which remains of pike are found increase compared to the number at which salmon remains are uncovered."
Research and study is being done to understand how salmons can be brought back like earlier times. River tributaries need to rehabilitated to bring back salmons to lay eggs on the river beds.The decrease in salmons has now captured attention of environmentalists and ecologists. It is now time to conserve the existing salmons before it becomes another extinct being.