A new study says that clownfish got smaller during a very hot ocean period in 2023. This happened in Kimbe Bay, Papua New Guinea. The study, in Science Advances, looked at 134 clownfish. It found that 101 of them became smaller at least once because of heat stress. Ocean temperatures are rising because of climate change. These high temperatures cause strong heat waves in the sea. This is bad for coral reefs and sea anemones, which are homes for clownfish. To survive, the fish shrink their bodies. Smaller fish need less energy and food.

Scientists think clownfish may change their bones to become smaller. Some male and female pairs shrank at the same time. But the female stayed bigger to keep the group’s social order. This was the first time this behavior was seen in coral reef fish. The study also showed that the clownfish could grow back to normal size when the ocean cooled down. This means they can change when the environment is hard. But experts are worried. If heat waves last longer in the future, shrinking may not be enough to help them survive.