Preliminary Results On The Cause Of Death Of 111 Dolphins In The Bazaruto Archipelago National Park, Province Of Inhambane
MAPUTO, MARCH 4, 2021 - Following the deaths of 111 dolphins of the species Stenella longirostris, in two separate incidents, on February 21 and 23, in the Bazaruto Archipelago National Park, Henriques Bongece, Deputy Minister of the Sea, Inland Waters and Fisheries, led an intersectoral mission to Inhambane Province, Vilanculos and Inhassoro Districts between February 24th and 27th, 2021.
The mission included staff from the Ministry of the Sea, Inland Waters and Fisheries, the Ministry of Land and Environment, the Eduardo Mondlane University and members of the Provincial Representative Council of the State of Inhambane.
In addition to the observations made on site, a network of regional and international experts was consulted, namely: the IUCN Cetacean Specialist Group; the International Whaling Commission and the Stranding Expert Panel for Africa and the Indian Ocean; as well as the IndoCet Stranding Issues Coordination for the Indian Ocean Region and the associate editor of the Scientific Journal on Marine Mammals.
These experts advised on the type of samples and information to be collected and suggested the most suitable laboratories to carry out the analysis of these samples. At the time, the Mozambican team was informed about the marine mammal stranding phenomenon that has been occurring in different parts of the globe and that, in many cases, it has not been possible to determine the cause thereof. The cases that are the least difficult to prove are those related to: overfishing; plastic pollution of the seas; noise pollution resulting from increased traffic at sea or the recent passage of military submarines; seismic activities associated with hydrocarbon exploration/exploitation; industrial development, including port construction; climate change, extreme events such as cyclones and the consequent change of the diet of marine animals; and tidal waves.
From the expert work carried out (at the site and from the examination of the animals), it was possible to verify the following:
- There are no visible signs of mutilation of the animals or contamination by hydrocarbons.
- The dolphins were found in the western part of Bazaruto Island (an area with a depth that varies between 3 and 7 meters) where they normally do not enter, and a “navigation anomaly” may have occurred.
- 23% of the dolphins had an empty stomach, which indicates that some of the 111 dolphins were not feeding on the spot.
- The dolphins' deaths resulted from beaching during low tide.
- At the time of the occurrence, there had been no seismic surveys in the region.
- The dolphins' deaths occurred during or shortly after the cyclone Guambe passed in the area.
- That similar phenomena had been recorded by the inhabitants of the Island in 1997 and in 2006, when a smaller number of animals were involved in both those cases.
To further study the causes of death, in compliance with the experts' recommendations, samples were collected and sent to specialized laboratories in and outside the country.
Of the two species of dolphins that occur in Mozambique, the spinner dolphins which were stranded are an oceanic species that travels to the open sea during the night to feed (in depths that vary between 10 and 50 meters) and during the day comes close to shore to rest, in areas with depths of up to 20 meters. It is a relatively abundant and widely distributed species along the Mozambique Channel, with a population estimated at between 10 and 15 thousand individuals and is not on the list of species in danger of extinction.
This mission was supported by the Bazaruto Archipelago National Park (BANP) and the Park's co-management partner, African Parks which is working in close coordination with the Government of Mozambique to help identify the cause of the mass stranding. The Park is managed under a Public-Private Partnership Agreement that was signed in December 2017 between the Government of Mozambique, represented by the National Administration of Conservation Areas (ANAC) and African Parks. African Parks is a non-profit conservation organization that takes on full responsibility for the rehabilitation and long-term management of national parks and protected areas in partnership with governments and local communities.
In addition to the occurrence of marine mammals such as dugongs, whales, dolphins and others, provided by the combination of shallow and deep waters, as well as the availability of nutrients and the tranquillity of the area, 180 species of birds, 45 of reptiles, 16 of land mammals, 500 of marine and coastal molluscs, and 2000 species of fish have been recorded in the Bazaruto Archipelago National Park.
The Bazaruto Archipelago National Park (PNAB), located in the province of Inhambane, has an area of 1,430 km2 and was created on 25 May, 1971, being the first marine park in the country.
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