Scientists discover new pale blue damselfish species in Maldives' deep-sea reefs

ts distinctive two-tone colouring—a pale blue underside and white top—offers camouflage against predators. (Image: Luiz Rocha)

A team of ichthyologists has uncovered a new species of damselfish off the Maldives' coast. The discovery, made during an expedition to deep-sea coral reefs, adds to the growing knowledge of marine biodiversity in less-explored regions of the Indian Ocean.

Exploring the Mesophotic Zone
The team, based at the California Academy of Sciences, used hand nets to collect, identify, and release fish from reefs below 100 metres. These depths, part of the mesophotic zone, receive minimal sunlight, creating unique habitats. Unlike well-studied shallow reefs, deep-sea reefs in the Indian Ocean remain largely unexplored.

The ichthyologists identified the new species at eight sites across the Maldives. Named Chromis abadhah, after the project's funders, the fish measures an average of 6.9 cm in length. Its distinctive two-tone colouring—a pale blue underside and white top—offers camouflage against predators.

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Adaptations of Deep-Sea Life
The team observed that C. abadhah tends to inhabit crevasses near sea sponges. Such areas are likely vital for protection from predators. They also noted that many mesophotic fish share similar adaptations, often occupying specific ecological roles. However, the precise niche of C. abadhah remains unknown.

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While deep-sea reefs are less affected by ocean acidification, they face other human-made threats. Discarded nets, ropes, and trash from ships, as well as bleaching events, endanger these ecosystems and their inhabitants. The researchers emphasised the importance of protecting these fragile habitats to preserve their unique biodiversity.