Aerial Survey for Dugong

Feb 12, 2008

Mission: Aerial Survey for Dugong in the Bazaruto National Park
Date: 12 February 2008
Requesting organisation: Nguni Productions for 50/50
Location:
Bazaruto National Park, Mozambique
Pilots:
Barry de Groot, Chris Rattray and Paul Dutton

Current Account of The Aerial Survey for Dugong in the Bazaruto National Park by Paul Dutton
Dugongs then and now
Dugong Population Trends
The Dugong Survey Team

This mission for The Bateleurs is one of very few in which Paul Dutton plays the part of a passenger, and not the pilot.  In fact, for this flight he was wearing his ecologist’s hat, and following the survey he produced a wonderfully detailed scientific report, from which we present the following extract:

Current Account of The Aerial Survey for Dugong in the Bazaruto National Park by Paul Dutton

“The Mozambique coastal littoral (i.e. the zone between the high and low tide marks) is blessed with many extensive inshore marine grass habitats suitable for the herbivorous Dugong, pictured above, which used to occur from Inhaca to the Rovuma River. The introduction of large mesh gill nets in 1976, set for the harvesting of sharks, has been the principal cause of the demise of the Dugong throughout their former range.

The Bazaruto Archipelago is situated in the Inhassoro and Vilankulu districts of the Inhambane Province.  It has extensive marine grass habitats which supported a widely distributed population of Dugongs, estimated at 150 animals in 1990. Since then at least 10 aerial surveys, up to February 2008, indicate that the population is now estimated to be less than 30, with only two nucleus breeding pairs. Most of the original study area is now depleted of Dugongs because of the trappings and subsequent incidental drownings.

Mozambique’s fisheries and Port Captain authorities continue to facilitate the use of gill nets within the boundaries of the national park.  This makes a very difficult task for the conservation authority – Direcção Nacional da Áreas da Conservação (DINAC) – which is charged with controlling the continuing destruction of the Dugong.

Dugongs have a very important niche in the marine environment.  They convert the little-used marine grasses into useful nutrients for the benefit of other mariner fauna, such as fish, and the reported reduction of fish catches in the two districts could be the result of the demise of the Dugong.”


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Dugongs then and now

Dyllan Smith, cameraman for Nguni Productions and 50/50, preparing to make the most of an aerial perspective.

“From 1969 until 2003 there were several reports of Dugong sightings in the vicinity of the Bazaruto Archipelago, and until the early 1970s there were  also accounts of Dugongs in other suitable sea grass habitats near Inhaca, Inhambane, Chitenguela, and Angoche. The intensification of large mesh gill netting from 1976, coupled with the lack of law enforcement, has been the principal cause of the decline of Dugongs in Mozambique.  This decline extends, as far as is known, up to the Somalia border with Kenya.

The population of Dugongs at Inhaca, once numbering about 20, is believed to be extinct also as a result of gill netting. Small numbers of Dugongs have been reported near Lingalinga, Inhambane, but their current status is not known.  The present situation at Angoche is also unknown, and my own enquiries indicate that Dugongs are now extinct on the northern coast of Mozambique.  There are reports from further north that Dugongs are now extinct on the Tanzanian coast, with only a few isolated groups in the Lamu district of Kenya.  So it appears that Bazaruto has the last remnant population of Dugongs, now numbering about 20 animals with only two breeding pairs, the rest being lone males.  

It is illegal to kill Dugong in Mozambique and the offence carries a fine of 50 000 000 Meticais, or 16 000 Rand.  However, there were no convictions on record until 2008 when a local fisherman was arrested for having the remains of a recently killed Dugong on his property. There is anecdotal evidence that flesh from captured Dugong was served on occasions at Margaruque island, and Vilankulo’s Port Captain once prepared a special meal of Dugong flesh for ex president Chissano!  It is only recently that gill nets have been banned in the vicinity of the Bazaruto Archipelago National Park, but illegal nets are still being set, some close to where the last breeding groups of Dugong occur.

Since 1990 systematic surveys of Dugongs within the Bazaruto area have been undertaken by various researchers using different methodologies and search intensities.  Aircraft have flown at altitudes varying from 100m to 150m, along selected transect lines with sample strip widths varying from 368 to 500 m. Low tide and calm periods were preferred for counting. The average flight time covering the study area varied from three to five hours.  Despite these varying methodologies, a useful indication of Dugong population trends has nevertheless emerged.  For the current survey a total of 14 transects 5km apart from abeam Inhassoro to Quewene Bay were flown at 80 miles/hour at an average altitude of 600ft ASL. Observations for this survey included animals recorded within an estimated 1000m on either side of the aircraft. Three observers participated in the survey.”


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Dugong Population Trends

Bateleur pilot, Barry de Groot, flying over Benguerua


“Whereas it was possible during earlier surveys to derive reasonable estimates using statistical analysis, the current sparse and unevenly distributed population makes this impractical and produces biased estimates.  For this reason the 2003 survey attempted a total count by increasing the search intensity to 35% over an extended flight time of five hours.  This total was augmented by reports of a number of individual animals from various operators in the study area.

After 18 years of survey there is little doubt that the current status of the Dugong is critical and immediate action must be taken to address the imminent extinction of the Bazaruto Archipelago Dugong. Credit must be given to the Direcção Nacional da Florestas e Fauna Bravia (DNFFB) and now Direcção Nacional da Áreas da Conservação (DINAC) for trying to prevent the use of gill nets in the proclaimed boundaries of Parque Nacional da Bazaruto, using limited means due to inadequate budgets – for example, there is no money to cover fuel costs for the patrol boat at Sitone.

It is recommended that future air surveys should concentrate effort where the last of the Dugong occur, according to the 2008 survey, and that transect lines should be established at least 1km apart to arrive at a total rather than sample count.  Also, funds should be sought to reinforce the current public conservation awareness campaign which could include posters for distribution throughout the Vilankulu and Inhassoro districts, as well as the provision of school exercise books with an image of a Dugong on the front cover and information on its usefulness on the inside cover, in both Portuguese and Xitswa.”


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The Dugong Survey Team

Standing, from the left:  Paul Dutton, Dyllan Smith, Chris Rattray, Ryan Logie and Richard Compton.  Crouching:  Nicky Troll and Barry de Groot.

Paul Dutton, Chris Rattray and Barry de Groot are Bateleur pilots.  Although a pilot, on this occasion Paul requested this mission and acted as the guide for the Dugong survey.  Dyllan, Ryan, Richard and Nicky comprised the four-person media team from Nguni Productions, contracted by 50/50.  Between them the entire team produced a very fine documentary describing the Dugong crisis which was screened by 50/50 on Monday, 17th March 2008 – with excellent coverage for The Bateleurs as well as the Dugongs.

Paul’s report, continued:
“The status of Dugongs in the entire Western Indian Ocean region, including the satellite islands, is critical.  This is due mainly to the use of gill nets set for harvesting sharks.  for their fins (Marsh, H. H 2001). The fact that there are still a few breeding groups in the Bazaruto population (estimated at 20) provides probably the last opportunity to save them from extinction.

The study area in which Dugongs occurred during the period 1990 until 1994 contained a well distributed population including a breeding nucleus of 30 animals. Recent surveys indicate these areas are now devoid of animals. The current survey shows that Dugongs are now concentrated near islands and Sanctuary.

Managing this smaller area will assist anti-poaching measures and the removal of illegal nets by all the lodges located in the Park, in collaboration with the Direcção Nacional da Areas da Conservação (DINAC).  Also, DINAC, which administers the Park, should be given the means to manage the remaining few Dugongs.

Acknowledgements:
Once again, The Bateleurs – Flying for the Environment in Africa responded to an urgent call for help by sourcing the pilots and aircraft and paying for the fuel for the survey of the Bazaruto National Park’s last Dugongs.  Bateleurs pilots Chris Rattray and Barry de Groot showed their piloting skills in getting our team of seven safely to Mozambique’s Bazaruto Archipelago, and again during six hours of precision flying along survey transects to obtain a count of the highly threatened Dugongs.

The 50/50 team comprising Nicky Troll, Richard Compton, Ryan Logie and Dyllan Smith must be commended for their hard work and enthusiasm in covering the labyrinthian eco-political intrigues that characterise Bazaruto’s highly threatened Dugongs.”

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