Have scientists discovered three new species of fish vital to UAE's reefs?

Scientists believe they have discovered three new species of tiny, colourful fish that are the foundation of the UAE’s coral reefs.

The bottom-dwelling fish are so small as to be virtually imperceptible and evaded previous surveys of Gulf reef fish, a conference at New York University Abu Dhabi heard on Monday.

But the diminutive marine creatures, known as cryptobenthic fish, are a diverse bunch that can account for up to 60 per cent of fish eaten in reefs.

Genetic testing will confirm whether new species have been identified. The study found an additional four species previously unseen in UAE waters.

The species were discovered during research on adaptation to the hot waters of the Arabian Gulf, where temperatures range from 16°C to 36°C, making it a favoured destination for scientists studying the effect of warming on the world’s oceans.

Biologists anaesthetised small patches of the reef with clove oil under a plastic cover to take stock of the reef’s biodiversity.

Of the 44 cryptobenthic species found in the Gulf of Oman, only 21 were found in the Arabian Gulf, where water temperatures are more extreme.

The slender fish are no larger than 40 millimetres and weigh less than two grams. They feed on algae and micro invertebrates and despite their importance to reef life, they have been overlooked as coral, sharks and larger fish typically get the attention.

Some live no more than 30 days, a short lifespan allows that makes them a good study for environmental adaptations.

“You have very rapid adaptation to different environment conditions so they’re very interesting to look at in terms of how they have solved the problem of extreme heat, for instance,” said Jacob Johansen, an assistant research professor at University of Hawaii and the leader of the study.

“You can get more information from those than some of the big fish that live 50 years.”

The potential new species appear closely related to Trimma coratinum, Hetereleotris vulgaris and Escenius pulcher but have different colouration.

For example, one potential new species resembling the Gulf blenny (Escenius pulcher) has bulkier eyes and a white belly.

The discovery of new species is not a surprise, said Mr Johansen.

“Honestly, when you look this deep into the reef, pretty much anywhere on the planet, you’re going to find something new.”

What was surprising was what the fish ate and what they did not. The study found species in the Arabian Gulf had a completely different diet to their relatives in the Gulf of Oman, even when the same food sources were available.

Fish regulate their body temperature depending on the surrounding environment. When water temperature increases, so will their metabolism and nergy needs, which could explain the change in diet.

“We need to understand why there’s a shift and what they’re shifting to and from,” said Mr Johansen. “If you’re relying on certain species to fulfill a role, that’s a fundamental shift you need to understand.”

The findings were presented on the opening day of a conference on coral reefs by NYU Abu Dhabi.

Species that may otherwise not warrant much attention can become critical when diets change, Mr Johansen said.

“We need to understand things like diet so we can understand how changing conditions are going to affect these fish,” said Alyssa Marshell, an assistant professor at Sultan Qaboos University.

“They’re the base of the food chain so we need to know what are they eating, whether it depends on the environment; if the environment changes is that going to influence their populations? If it does, that will fall on to the rest of the ecosystem.”