Anomaly in the Arabian Sea
Approximately 19 kilometers off the coast of Murudeshwar in Karnataka lies Netrani Island, an uninhabited outcrop that harbors one of the most significant coral reef ecosystems on the west coast of India. The island's location is unusual for substantial coral growth, as the western Indian coast is subject to strong monsoon seasons and river runoff, which typically create conditions too turbid and variable for sensitive coral species. Despite this, Netrani supports a patchy but dense reef system.
The reason for this biodiversity is the local oceanography. The island's isolation from the mainland limits sediment runoff, resulting in clearer waters with visibility that can reach between 15 and 30 meters. This clarity allows sunlight to penetrate, supporting the symbiotic algae essential for coral health. The island's geology and its position in the Arabian Sea also facilitate conditions favorable for coral settlement and growth, creating a small but resilient ecosystem. A 2006 underwater census by the Central Marine Fisheries Research Institute first documented the reef's scientific importance, revealing 14 coral species from 11 genera. Subsequent studies have identified even greater diversity, including sensitive species from the family Acroporidae, which are rare in the patchy reefs of the eastern Arabian Sea.
A concentration of marine life
The coral structures of Netrani Island provide a complex habitat that supports a high concentration of associated fauna. Surveys have documented at least 92 species of fish in the island's immediate vicinity. The fish population includes common reef dwellers like butterflyfish, parrotfish, triggerfish, and moray eels. The ecosystem also attracts larger pelagic species. Whale sharks (Rhincodon typus), the world's largest fish, are sighted here, along with occasional reports of orcas.
The biodiversity extends beyond fish. Researchers have cataloged numerous invertebrates, including 48 species of gastropods, 17 species of crabs, 7 species of nudibranchs, and 6 species of sponges. Netrani hosts the giant clam (Tridacna maxima), an IUCN red-listed mollusc. Its presence here marks the first time the species was recorded in the mainland Indian waters. The reef also supports two IUCN Red Listed fish species: the humphead wrasse (Cheilinus undulatus) and the whale shark. The island itself, covered in dense vegetation, is a nesting site for pigeons—which gives it the name "Pigeon Island"—and white-bellied sea eagles.