Atlantic Salmon Display Ability to Adjust to Warmer Waters

Atlantic salmon, known as the king of fish, displays an astonishing ability to adjust to warmer temperatures, a new study discovers.

Atlantic salmon population, native to North Atlantic, has dramatically declined in the last 30-40 years and much of the decline has been blamed on the change in marine environment. But, a group of scientists at the University of Oslo and University of British Columbia have found that this magnificent fish very well adjusts to warm temperature that is seen with climate change.

The findings were based on the observation of wild salmons from two European rivers. They focused on the salmon population thriving in the cold waters of Norway's Northern Alta River, where water temperature has not crossed 18 degree C over the last 30 years. They also looked at the warm-water population in France's Dordonge River that is located 3,000 kilometers south, and the annual temperature in this region regularly crosses over 20 degree C.

The researchers compared the cold-water population with the warm-water population. Eggs collected from these populations were transferred to the University of Oslo, where they were hatched and raised at 12-20 degree C. Despite being raised in a substantially different natural environment, the eggs from both population displayed similar capabilities when warmed.

The researchers noticed that when both the populations were reared at 12 degree C, the salmons developed cardiac arrhythmias at 21 to 23 degree C, after a maximum heart rate of 150 beats per minutes. But, those who were raised at 20 degree C developed cardiac arrhythmias at 27.5 degree C, after heart rate reached 200 beats per minute. They noticed that by increasing the fish's acclimation temperature by 8 degree C, the temperature tolerance increased by 6 degree C.

Cardiac arrhythmia is condition that disrupts the heart's normal rhythm due to which the heart may beat either too fast or two slowly and causes breathlessness, weakness or dizziness.

"The results are surprising," Farrell said. "A fish faced with uncomfortably warm temperatures might relocate or even die if it is too extreme. Here we have evidence for warm acclimation of a commercially and culturally important fish species."

The findings were documented in the Nature Communications.