Extreme Winters Affect Fish Habitat: Study

A study has been conducted in order to understand the importance of winter conditions for fish in streams and rivers in cold regions.

The study, conducted by ecologists from the Umea University and the Norwegian University of Science and Technology, has found that extreme conditions which involve ice formation and ice breakup vary over time and affect not just the non-living river environment, but also the fish.

Those streams that fill with ice kill all the fish that are trapped. These fish get killed as they failed to swim back to the backwaters that are not frozen. They noticed that the juvenile fish were more vulnerable to this.

According to the researchers, the change in the streams and rivers in winter is due to human activities.

"Rivers that have been exploited for hydroelectric power can be especially hard for fish to live in, because the way hydropower is produced often means that the flow changes radically very quickly and often, which can lead to repeated ice break-ups and a great deal of anchor ice formation. When the ice cover at the surface disappears, cold air is fed downward in the water and forms ice crystals that cover the bottom, making it hard for fish to survive," lead of the study Christer Nilsson from Umea University was quoted as saying in Phys.Org.

The researchers conclude that more measurements are needed in order to predict the time at which the situations in waterways rise and how fish are affected by the extreme events. In order to be able to manage streams and rivers in a long-term sustainable manner, more attention has to be given to the future changes in climate.

According to Nilson, the predictions of winter climate in the future show that there will be more back and forth between the melting of ice and frost, causing more unstable ice conditions, rains, flooding and a lot of challenges for the fish to survive.

The findings are published in the journal BioScience.