Researchers predict that fish will shrink in size by 20 to 30 percent if ocean temperatures continue their upward climb due to climate change.
This is the findings of a new study in Global Change Biology by the University of British Columbia. The reason for this future decline in size stems from the fact that fish are cold-blooded animals, and are thus unable to regulate their body temperatures.
“When their waters get warmer, their metabolism accelerates and they need more oxygen to sustain their body functions,” said co-author William Cheung, associate professor at the Institute for the Ocean and Fisheries and director of science for the Nippon Foundation-UBC Nereus Program.
He added that “there is a point where the gills cannot supply enough oxygen for a larger body, so the fish just stops growing larger.”
Lead author Daniel Pauly is the principal investigator of the Sea Around Us at the Institute for the Ocean and Fisheries. He explained that the fish’s need for oxygen increases as the fish becomes an adult, due to the increase in their body mass. However, the surface area of the gills does not grow at the same pace as the rest of the body. He calls the set of principles that explain why fish would shrink as “gill-oxygen limitation theory.”
The presence of climate change will result in less oxygen in the oceans. This is further compounded as the warmer weather increases the fish’s oxygen requirements. With a smaller oxygen supply, the fish would be forced to stop growing at a smaller size so as to be able to fulfill their needs with the smaller oxygen supply available.
Some species may be more affected by this combination of factors. For fisheries, the fish’s shrinking size greatly impacts fisheries production and the fish’s relationship with other organisms in the marine ecosystem.