Finding Nemo may get much harder


As the world’s oceans warm, we may stop trying to find Nemo and wonder where are have all the clownfish gone, say researchers.

Scientists have discovered that clownfish, made famous by the animated-movie Finding Nemo, become stressed and give birth to less young when their home anemone become bleached from ocean warming.

Corals and anemone are marine animals that lose their green-pigmented symbionts called zooxanthallae when water gets too warm. Without zooxanthallae, anemone die.

Suzamme Mills and her colleagues from Paris Sciences et Lettres (PSL) Research University studied 13 clownfish at Moorea Island in the South Pacific during an unusually warm 2016 summer.

The team studied the fish and their anemone for 14 months before, during and after El Niño weather caused temperatures in the lagoon to rise above the mean average to 29.3C.

They found that clownfish couples that lived in an anemones that could endure the heat had higher reproductive hormone levels and spawned more frequently compared to their stressed counterparts in bleached anemone.

The fish in bleached anemone had higher stress hormones and produced fewer viable young, the researchers found.

The findings, which were published in the scientific journal Nature Communications this week, highlight the cascading effects of warming oceans with hormone stress responses playing a crucial role in changes to population demography.

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