The global oil and gas survey company Searcher is gearing up to blast powerful sound waves into the Indian Ocean, directly adjacent to the last viable population of dugongs on Africa's east coast.

Searcher's hydrocarbon target area is a massive 42,000km2 swathe of sea adjoining the Bazaruto Archipelago National Park, a chain of five islands in central Mozambique famed for their idyllic white sand beaches, coral reefs and clear blue waters that make for exceptional diving and snorkelling.

Bazaruto is also home to the mermaid-like dugong, a beleaguered marine mammal that feeds on seagrass meadows. The neighbouring sea is considered to be a globally important living space for whales, dolphins, sea turtles and other marine species.

During the 1960s, large herds of hundreds of dugongs were reported as far north as Kenya and Somalia, but over recent decades their numbers have plummeted. The most recent scientific studies suggest there are now fewer than 250 adult dugongs left along the east African coast - and Bazaruto is home to about 90% of these survivors.

Just last year, the International Union for Conservation of Nature (IUCN) reclassified the east African dugong population as "critically endangered", the highest level of risk before a species is declared extinct in the wild.

Nevertheless, the Perth-based Searcher group has set its sights on a major 3-D seismic survey near Bazaruto that involves blasting sound waves into the...