GILL-OXYGEN LIMITATION THEORY (GOLT)

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• According to Gill-Oxygen Limitation Theory (GOLT), 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.