Among various ways in which climate change is impacting life on Earth, one has been to change the distribution of fish species in the oceans. Scientists have predicted that the shift will be towards the poles. In a new research paper, they have explained the biological reasons why fish species will follow that direction.
It stems from the way fish breathe. Scientists describe this with the Gill-Oxygen Limitation Theory, or GOLT.
Daniel Pauly, the author of the theory, is the principal investigator of the ‘Sea Around Us’ initiative at the University of British Columbia’s Institute for the Oceans and Fisheries. His new paper is published in Mediterranean Marine Science (ejournals.epublishing.ekt.gr/index.php/hcmr-med-mar-sc/article/view/19285/18618).
A statement on the ‘Sea Around Us’ website explains the theory. Warming waters have less oxygen. Therefore, fish have difficulties breathing in such environments. Additionally, such warming, low-oxygen waters also increase fish’s oxygen demands because their metabolism speeds up.
This is because, as fish grow, their demand for oxygen increases. However, the surface area of the gills (two-dimensional) does not grow at the same pace as the rest of the body (three-dimensional). The larger the fish, the smaller its surface area relative to the volume of its body.
So, the fish move to waters whose temperatures resemble those of their original habitats and that satisfy their oxygen needs.
As the global sea surface temperature has increased by approximately 0.13°C per decade over the past 100 years, “suitable” waters are more and more found towards the poles and at greater depths.
Previous studies by Pauly and his colleagues have already predicted that climate change will cause some fish species to shift their distribution by more than 50 km per decade, the statement said.
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