Warmer Waters from Climate Change Could Lead to Smaller Fish

As we humans continue to treat mighty oceans like a toilet at a frat party, our piscine cohabitants on this planet continue to bear the brunt of our plastic-fueled charge toward mass extinction. As if accidental sex changes and being forced to eat garbage weren't enough of an imposition by land-dwelling species (well, namely people), warmer waters could also be making fish smaller in the future.

That's according to a new study from the University of British Columbia (UBC), estimating that individual fish could be shrinking in size by 20 to 30 percent in coming years. And it all comes down to gills, says William Cheung, study co-author and associate professor at UBC's Institute for the Ocean and Fisheries.

"One of our major findings is that climate change is affecting the body size of fish, particularly in oceans," Cheung explained to MUNCHIES. "Fish gills absorb oxygen from the water, but there is only a limited amount of surface on gills."

Unlike mammals, which are warm-blooded by definition, fish do not regulate their body temperature via skin and sweat and shivering. As a result, when waters heat up, the fishes' metabolism accelerates, and their gills need to extract more oxygen from the water for basic functions like feeding and breathing.

Eventually, Cheung and co-author Daniel Pauly argue in their paper, the fish "cannot get sufficient oxygen to support further growth, at which point the fish will reach its maximum body size." In other words, the fish just stops growing.

So, why is this a bad thing? Cheung says that shrinking fish could have a significant impact not just on their immediate ecosystem, but on the humans who fish them.

"Big fish eat the small fish, and that's how most marine ecosystems function. So, changes in the body size of fish really affects the predator and prey interaction and ecosystem dynamics, and that makes it very difficult to predict how the ecosystems will be affected. Ultimately, it could affect fisheries and other benefits we obtain from fish stocks."

Sure, those fish could pack up and move to cooler waters, but that's not exactly the best case scenario, especially for fisheries and other animals who depend on fish stock for survival.

"The tropical area will become so different that many fish stocks will find it difficult to live unless they really change their biology and their lifestyle. That could lead to local extinction, meaning that many species will move away from the tropics. Other fish stocks might move to areas like the arctic because of rising ocean temperature."

With mathematical modeling, Cheung and Pauly project a 20 to 30 percent decrease in body size due to ocean warming, something Cheung attributes to human activities that produce greenhouse gas and require the burning of fossil fuels.

As if things weren't already looking bleak for our California rolls, now even more sustainable sushi could be threatened by our changing planet. And that's, quite literally, just the tip of the iceberg.