State of the Environment in
Vennesla 2001

 
Norsk

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The Salmon in Otra 

Through the ages Otra has been a central part of the industry in Vennesla. The 24,5 mile long river floats through Aust-and Vest-Agder. Fishing for salmon is popular in Otra. Today the salmon fishing area stretches from The Vigeland falls and down to Kristiansand.
	The picture is taken at Heisel, by
	Vigeland Hovedgård

For over 30 years the river Otra has been without a viable population of salmon. Up to The 1960`s there was an own population of salmon in Otra. This population was well known for its great size of the fish. Back then, it was possible to catch salmon up to 30 kilos. The salmon disappeared in the 1960`s, and the main reason was local pollution and acid rain. Many believe that the pollution of Otra is only caused by the local factories, but acid rain from other places is actually the main reason. The acid rain comes mainly from Great Britain and central Europe.

The river has been whitewashed as an attempt to make the river viable for salmon. And as a result of this, the salmon came back in the early 90`s. And from 1993, it has been possibilities for organised fishing in the river. The original Otra salmon will never come back, but there is great optimism for establishing a new viable population of salmon.

In 1995 salmon fry was discovered for the first time in many years, and the optimism was great. But in 1997, a large amount of aluminium waste was dumped in the river. The aluminium waste kills the fish in two ways:It suffocates the fish by clogging the gills, and it also removes the calcium between the cells in the fish body, and the cells desintegrate. This resulted in a large amount of dead fish in the river and the salmon fry got considerably weakened. But in the years after this event the salmon in Otra has again recovered. Another reason for this is that the industrial waste was led directly in to the sea through pipes. Earlier this waste was dumped in Otra.

The table shows an overview of the salmon fishing in Otra. From 1980 and up to 1993 there was no organised fishing, therefore no catches of salmon was registered. After 1993 the catches has varied some, which is caused by the low water level. The temperature in the river and acid rain are also important factors.

The table shows pH-values from the period of 1987- 1999. After the registration started the river has more and more been neutralised. As a result of the reduction of acid water, the population of salmon has increased over the last years.

As the table shows, the possibilities for a future salmon population in Otra look bright. The pH-value is getting closer to a perfect level for the fish. But if a new population of salmon is going to be a reality, we are dependent on no polluted waste dumped into the river, like in 1997. Back then, the pollution did not cause the serious consequences as expected. The fish could as soon as the year after, return to the river again. But the question is if the river is able to take the same amount of pollution once more?