THEY are the brilliantly coloured small fish familiar to most people from the hit movie Finding Nemo, but now Scottish scientists are seeing clownfish as key sufferers of the effects of global warming.

Clownfish live in a symbiotic relationship with sea anemones, hence their alias anemonefish. They live in warm water mostly on the fringes of the Indian and Pacific Oceans and are particularly associated with the Great Barrier Reef off Australia.

Closely related to coral and jellyfish, sea anemones catch their prey – usually small fish – in their poisonous tentacles, but clownfish are immune and live happily alongside the anemones which attach themselves to rocks and coral.

In recent years, the phenomenon of “bleaching” anemones has affected clownfish which shelter among the anemones’ tentacles and lay their eggs at the base of those tentacles. It is known that bleaching, which also affects coral, takes place because increasingly warmer water kills the algae that dwell in anenomes and coral and provides their vivid colour.

Scientists had already proved that the bleaching was directly related to increased sea temperatures associated with global warming, but now the Glasgow team has shown that clownfish are being affected too, principally through stress.

Clowfish are particularly good for study since unlike the heroes of Finding Nemo, they are sedentary creatures who rarely stray far from home.

Last year French scientists and local researchers showed that clownfish that lived in bleached anemones were suffering fertility problems, and in some areas it was a threat to the species’ existence – the first time that such a link had been found.

Now scientists at Glasgow University’s Institute of Biodiversity, Animal Health and Comparative Medicine (IBAHCM) have gone further. A team led by Dr Tommy Norin went to French Polynesia to conduct experiments and research which were published earlier this week by the Royal Society.

They took 16 clownfish and split them between two tanks, one with ordinary healthy anemones and own with bleached anemones that had no algae.

The findings based on studying how much oxygen each set of clownfish used were conclusive, proving that the fish residing with the bleached anemones had a higher metabolic rate and needed to use more energy just to stay alive.

The report’s summary states: “As climate warming is expected to affect the physiology, behaviour and life history of animals, including ectotherms such as fish, we measured if residing in bleached versus unbleached sea anemones affected the standard (ie baseline) metabolic rate and behaviour (activity) of juvenile orange-fin anemonefish.

“Metabolic rate was estimated from rates of oxygen uptake, and the standard metabolic rate of anemonefish from bleached anemones was significantly higher by 8.2 per cent compared with that of fish residing in unbleached anemones, possibly due to increased stress levels.

“Activity levels did not differ between fish from bleached and unbleached anemones. As reflects the minimum cost of living, the increased metabolic demands may contribute to the negative impacts of bleaching on important anemonefish life history and fitness traits observed previously (eg reduced spawning frequency and lower fecundity).”

The implications of the study are clear – it is not only coral and sea anemones which are suffering from global warming, but fish, too.

Dr Norin told the New York Times: “At some point, we will open our eyes and see that we really need to do something.”