– I saw between 100 and 200 dead fish

The researcher believes that horse mackerel does not tolerate fresh water.

Magne Ivar Fauskanger lives in Onarheim in Tysnes. On Saturday he walked along the boardwalk and was surprised to see many dead fish.

– I saw between 100 and 200 dead fish and called the Directorate of Fisheries, he says.

The police were also notified of dead fish, but of Os.

– We know that there are many dead and half dead fish in Bjørnfjorden. The Directorate of Fisheries has been notified, says Per Algrøy, director of operations in the West Police District.

Åse Møller-Hansen found 17 dead fish in Mobergsvika on Saturday. Another person also reports dead fish in Vargavågen, writes Os & Fusaposten.

Have a theory

BT has contacted the Directorate of Fisheries, which states that it is aware of the case. Communications director Anette Aase says they haven’t moved.

Leif Nøttestad is a Principal Investigator at the Institute for Marine Research. Please confirm that the images BT has received are of dead horse mackerel. It is a good food fish, especially sought after in Asia.

Nøttestad emphasizes that he does not have an exact answer as to why so many fish have died, but he does have a theory:

– We have a long and cold period behind us that has cooled the sea. It has been almost windless, and this has led to stratification or stratification of the water bodies. Over time, a layer of almost pure fresh water has been separating towards the surface. It freezes to zero degrees and is in the upper water layer above the heaviest salty seawater, says Nøttestad.

– A death trap

He believes that horse mackerel may have emerged in a freshwater layer and died as a result of not being able to withstand the transition from saltwater to freshwater.

– It’s probably a death trap for horse mackerel if they swim in bodies of water that are very cold and contain very little salt, says Nøttestad.

He states that there are many saltwater fish that cannot tolerate fresh water.

– So I think this may be a likely answer, but I must emphasize that this is just a hypothesis, says Nøttestad.

– Why was only horse mackerel found and no other dead fish?

– I can’t answer that, but it may have to do with the behavior of horse mackerel, which possibly searches higher in the water column part of the day, than other species of fish in winter. Usually such behavior will be harmless to horse mackerel, but not as the situation has been this winter.

A sure answer requires a closer examination of both the fish and the sea, according to the researcher.