Shrinking Trout

When the weather is terrible and temperatures outside plummet, it's good to know that many of us can retreat into warm homes with a hot cup of tea. But other creatures aren't quite so lucky and often have to resort to ingenious methods to make it through the cold months.

For example, scientists based in Norway and Finland have made the startling discovery that some fish can actually shrink during particularly harsh winters. This rare survival trait has been seen before in some small mammals, including shrews, and in lizards, however, this is the first study to conclusively show that fish can also shrink.

Using experimental pools, scientists simulated a cold winter, controlling the water temperature and current and even adding a covering to mimic ice coverage. The results showed that under these harsh conditions, juvenile brown trout shrunk by as much as 10% of their body length.

It's believed that this could help the young fish to conserve energy when food is in short supply, but the scientists are not yet certain about what exactly causes the shrinkage, hypothesising that it's due to a reduction in the volume of a jelly-like substance within the vertebral discs of the fishes' spines, thus leading to shortening of the spinal column.