🌅 Clownfish Shrink to Beat Climate Change

SOURCE

Versteeg et al. (2025)

WHAT TO KNOW

• Researchers at Newcastle University in the U.K. observed 134 wild clownfish off the coast of Papua New Guinea during a marine heat wave beginning in March 2023, finding 100 of the fish shrank over the following five months as the waters warmed and lost oxygen. The team found the fish that shrank increased their odds of survival by 78% compared to the fish that didn’t shrink.

WHY IT MATTERS

• Clownfish aren’t the only species that appear to shrink when facing rising temperatures; studies show birds shrunk by 2.6% from 1978 to 2016 as the climate warmed, while rising temperatures have been linked to reductions in the sizes of small mammals and other marine life. However, the researchers of the present study say their findings are particularly surprising as the clownfish appeared to shrink in a matter of mere weeks in response to the marine heat wave, rather than gradually losing size while adapting to broader climate shifts.

CONNECT THE DOTS

• The marine heat wave observed in the present study is part of the world’s ongoing fourth global coral bleaching event; the second such event in the last decade. As of March 2025, a staggering 84% of the world’s reefs are impacted by the event, making it the most intense global bleaching ever recorded.