Fish species failing to adapt to warming oceans

Biotest study species European perchA research project associated with Sweden’s University of Gothenberg has found the impact from steadily rising ocean temperatures could prove fatal for some fish species. As well as the loss of biodiversity in the world’s oceans, the impact from warming seas on both marine mammals, and human populations that rely heavily on fish as a food source, would also be dramatic.
University of Tasmania senior research fellow Timothy Clark was a member of the Swedish team that conducted tests during 2012 and 2013 on European perch (Perca fluviatilis) from the ‘Biotest’ lake enclosure in the Baltic Sea. For over 30 years, these fish have been subjected to the lake’s ‘elevated’ water temperatures that are heated by the nearby Forsmark nuclear power plant.
The tests were also conducted on ‘reference’ fish populations from outside the enclosure, and results showed that while the fish are able to adapt their resting physiological functions to slowly rising temperatures, their maximum physiological functions are far less flexible.
“The fish can increase their lethal temperature by a certain amount, but they can’t keep up with the current rate of global water temperature increases,” Clark said.
The scientific team found that when the reference populations outside the enclosure were warmed quickly, their resting metabolic rate rose dramatically, compared to the lake fishes’ lower resting metabolic rates at the same temperature.
According to Clark this showed the Biotest fish had adjusted to temperature increases over time, although since the maximum capacity for oxygen uptake did not differ between the two groups, their ability to adapt to changing environmental conditions was probably still limited regardless of the timeframe.
“There’s been a lot of speculation about what fish populations will look like in 100 years, but this is the best evidence to date that fish aren’t going to be able to adjust indefinitely – which is why we have to manage greenhouse gas emissions and try to limit global temperature increases,” he said.
Results of the research have been published in the journal Nature Communications.
Clark will return to Sweden in 2017 to conduct further testing with the two perch populations.
Anne Layton-Bennett