Honey, I Shrunk Our Dinner: Climate Change Is Turning Big Fish Into Little Fish

Warmer oceans could lead to a body size decline of up to 24 percent.
In the future, it’s possible that these juvenile cod fish may seem absolutely huge. (AFP/Getty Images)
Sep 30, 2012
A former Gourmet staffer, Lawrence enjoys writing about design, food, travel, and lots of other stuff.

I recently highlighted NYC Commissioner of Health and Mental Hygiene Thomas Farley’s efforts to encourage the city government to impose limits on portion sizes as part of its strategy for combatting America’s obesity epidemic.

Well, it appears that global warming could start to play an unexpected role in Farley’s quest when it comes to the serving size of your favorite seafood dishes.

“The biggest fish in the sea could be almost 25 per cent smaller by 2050 because of global warming,” reports The Independent. “Warmer oceans will carry less dissolved oxygen, causing fish to grow to smaller sizes and forcing them to move to cooler waters, the research published in the journal Nature Climate Change claims. Scientists predict that a rise in global temperatures over the coming decades will cause the average body size of sea fish to decline by between 14 and 24 per cent.”

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ScienceDaily adds that, “The researchers used computer modeling to study more than 600 species of fish from oceans around the world . . . with the tropics being one of the most impacted regions.” And they quote the study’s lead author, Dr. William Cheung, from the University of British Columbia (UBC), who observed, "We were surprised to see such a large decrease in fish size . . . Marine fish are generally known to respond to climate change through changing distribution and seasonality. But the unexpectedly big effect that climate change could have on body size suggests that we may be missing a big piece of the puzzle of understanding climate change effects in the ocean."

Reporting on the same study, BBC News also quoted Dr. Chung explaining that, “As ocean temperatures increase, so do the body temperatures of fish . . . Rising temperatures directly increase the metabolic rate of the fish's body function . . . This leads to an increase in oxygen demand for normal body activities. So the fish will run out of oxygen for growth at a smaller body size."

Interestingly, the idea that fish growth is limited by oxygen supply was suggested more than 30 years ago by Daniel Pauly, principal investigator with UBC's Sea Around Us Project and the current study's co-author. ScienceDaily quotes Pauly as saying, "It's a constant challenge for fish to get enough oxygen from water to grow, and the situation gets worse as fish get bigger . . . A warmer and less-oxygenated ocean, as predicted under climate change, would make it more difficult for bigger fish to get enough oxygen, which means they will stop growing sooner."

These findings seems to mesh with a report earlier this year by the Swiss Broadcasting Corporation that stated, “Global warming could lead to more of the world’s oceans becoming ‘dead zones’—where a lack of oxygen leads to marine life dying out . . . Oceans are already oxygen-starved in places: every summer some areas of the northeastern Pacific see huge numbers of dead fish, shrimp or mollusks washed up on beaches. Currently around 15 per cent of oceans are considered oxygen-depleted.”

So it appears that we’re still learning a lot about the way ocean ecosystems work and need to continue to research the human impact on these delicate environments.

What steps do you think we should be taking to try and reverse the effect of climate change on the world’s oceans?

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