Fish are expected to shrink in size by 20 to 30 per cent as a result of rising ocean temperatures due to climate change across the globe, claims a study.
The findings showed that as fish grow into adulthood, their demand for oxygen increases because their body mass becomes larger. However, the surface area of the gills — where oxygen is obtained — does not grow at the same pace as the rest of the body.
This explains why fish are expected to shrink — “gill-oxygen limitation theory.”
“Fish, as cold-blooded animals, cannot regulate their own body temperatures. When their waters get warmer, their metabolism accelerates and they need more oxygen to sustain their body functions,” said William Cheung, Associate Professor from the University of British Columbia in Canada.
“There is a point where the gills cannot supply enough oxygen for a larger body, so the fish just stops growing larger,” he added.
Warmer waters increase fish’s need for oxygen but climate change will result in less oxygen in the oceans. This means that gills have less oxygen to supply to a body that already grows faster than them.
This forces fish to stop growing at a smaller size to be able to fulfill their needs with the little oxygen available to them, the researchers said, in the paper published in the journal Global Change Biology.
Some species like tuna, which are fast moving and require more energy and oxygen, may shrink even more when temperatures increase.
Smaller fish will have an impact on fisheries production as well as the interaction between organisms in the ecosystems, the researchers said.