Saving Mozambique’s dugongs

by Dr Garth Cripps, Senior Conservation Scientist & Forest Carbon Finance Specialist, Madagascar

Walking down the lively streets of Vilanculos and Inhassoro in Mozambique it is difficult to believe that in the early 90’s these were dead towns. The streets, shops and houses empty, as all but a few people fled the civil war. Many took refuge on the nearby islands of the Bazaruto Archipelago, where the sea provided them with some shelter.

Mozambique’s civil war ended in 1992, but the Bazaruto area is still a place of refuge. For here survives what is thought to be East Africa’s only remaining viable population of dugongs.

As early as the late 80’s and early 90’s and despite the war, Asian demand for shark fins had reached this isolated part of southern Africa. Many local fishers turned to shark fishing using gillnets. Dugongs are particularly prone to being caught in these nets. Shark fishing continues to this day and is the main threat to the survival of dugongs in Bazaruto.

Dugongs belong to the order Sirenia – derived from the sirens of Greek mythology. Sirenia are part of an odd and seemingly dissimilar array of living mammals (the superorder Afrotheria), which includes golden moles, the aardvark, elephant shrews, tenrecs, hyraxes and elephants. The common ancestry of dugongs and elephants is reflected in their strikingly similar reproductive biology.

Dugongs take several years to reach sexual maturity, have a long gestation period of 14.5 months, and usually bear a single young that is dependent on its mother. This slow life cycle makes dugongs particularly vulnerable to hunting and accidental bycatch.

In a letter he wrote in the 1930’s, a lighthouse watchman from Inhambane Bay, northeast of Maputo, described enormous herds of dugong roaming the bay.

Now the only known population is that of Bazaruto – estimated at 247 individuals.

Taking into account natural mortality, models show that a population of 247 is possibly viable. But if just two reproductive females are killed a year, the population will not survive long term. If three reproductive females are killed a year, East Africa’s dugongs are effectively going extinct.

Known catches of dugongs in the area are presently three a year. Most of these are adult females. The reasons for this are unclear, but one explanation is that young, less weary dugongs stumble into the shark nets. The bond between the mother and its young is such that she won’t leave it and becomes entangled in her efforts to help it.

Over the next three days Blue Ventures will help diverse stakeholders put together a project, funded by the Global Environment Facility, to conserve the dugongs and seagrass of Mozambique. We’ll bring our experience to bear in designing community-based conservation, social marketing campaigns, sustainable financing mechanisms and strengthening the law to conserve dugongs. Measures all meant to tackle the complex problem of conserving dugongs.

But really our remit is simple. Two numbers: three to zero.

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