THERE are four most commonly found species of marine mammals in the near coastal waters of Sarawak Indo-Pacific bottlenose dolphin (Tursiops aduncus), Indo-Pacific humpback dolphin (Sousa chinensis), Indo-Pacific finless porpoise (Neophocaena phocaenoides) and the Irrawaddy dolphin (Orcaella brevirostris).
All of these marine mammal mentioned are living within the waters in vicinity to human population in the coastal areas. An exceptional case is for the Irrawaddy dolphin because they are found to travel even in the upper stream of the riverine system.
Irrawaddy dolphins can live and survive even in waters with low visibility; murky estuarine. In Sarawak, they can be found in the waters of Santubong, Lundu coastal waters, Muara Tebas, Rajang delta, and even in Baram and Kuala Lawas. Their large range of distribution puts them at risk to anthropogenic threats.
Irrawaddy dolphins are a very graceful swimmer. Unlike most spinner dolphins and bottlenose dolphins, Irrawaddy dolphins does not leap out of water and spin in style. They just gracefully breach for the exchange of breath, with some occasional mid-air rotation.
Besut is the name fishermen used to refer to the creature with rounded head and a small dorsal fin breaching in water and coming near their fishing boat; the Irrawaddy Dolphin. They can easily be found to swim near fishermen boats or in areas nearby fishing stakes. They are a wonderful sight to children and tourists alike.
This friendly creature likes to hang out near fishermen, which sometimes puts them at risks of boat strike, or incidental catch. Although boat strike is a rare event as a cause of death for Irrawaddy dolphin, incidental catch however, occurs quite frequently. Their ability to communicate through clicks, creaks and buzzes for echolocation is helpful to travel in waters with low visibility and avoid boat strike danger. They usually die due to drowning in fishing nets; being tangled, unable to escape and drown themselves to death.
In Sarawak, at least 3 reported case of stranding of irrawaddy dolphins which were resulted from incidental catch. The maximum lifespan of Irrawaddy dolphin is somewhere between 30 to 35 years. It is thought to be an alarming situation if the yearly death of Irrawaddy dolphin from unintended bycatch cannot be reduced. Their extinction can cause imbalance to the fisheries stock we have in the aquatic system.
Ignorance to this basic knowledge can put the species to a very close call to extinction. The same case as it was with the Irrawaddy dolphin in Cambodia, the river dolphin in Yangtze river, China. Negligence is the contributing factor to their extinction. That is usually the case when national agenda of development excludes the importance of biodiversity conservation.
While we can still see them around, it is time to gather the support of all stakeholders from all walks of life to try and slow down, or if possible, stop the extinction rate of our graceful riverine and coastal resident, the Irrawaddy dolphins. – SN
