Dolphins act as indicators of marine and freshwater health in the basins where they live. However, their habitats often overlap with areas of intensive human activity, which poses threats to their survival.
Dolphins of the Rajang: A call to protect our aquatic neighbours
The mighty Sungai Rajang, the longest river in Malaysia, supports a significant wetlands area that provides invaluable socio-economic benefits to both people and the environment.
It supplies the surrounding human population with resources such as food and water, and services like transportation, power generation, recreational activities, and opportunities for income generation through tourism.
The river is also an important area for research and educational activities and is home to the Irrawaddy dolphins, locally known as empesut.
According to a study published in the Journal of Malaysian Applied Biology by Bali et al. (2017), these dolphins have been recorded in the Rajang, Sematan, Bako, Muara Tebas, Saribas, Igan, Lupar, and Lassa rivers, as well as in the coastal waters of Bintulu, Mukah, Sebuyau to Pulau Burong, Kabong to Pulau Bruit, and Lawas.
Did you know that river dolphins act as indicators of river health in the basins where they live?
If the dolphin population in a river is thriving, then the overall state of that freshwater system is also likely flourishing. However, if that population is on the decline, it’s considered a red flag for the ecosystem as a whole.
These dolphins are also described as “facultative” river cetaceans due to their flexibility to inhabit both marine and freshwater environments.
Sadly, the Irrawaddy dolphins are classified as “endangered” on the International Union for Conservation of Nature’s (IUCN) Red List.
The Rajang mangroves: A habitat for dolphins
The Rajang delta is a busy waterway that includes deep anchorage port operations and various other industries.
According to a rapid survey by the World Wide Fund for Nature-Malaysia (WWF-Malaysia) in 2015, the Rajang delta is regarded as one of the key habitats for wildlife, including dolphins, and deserves long-term conservation attention.
The delta is also home to protected species under the Sarawak Wild Life Protection Ordinance 1998, such as proboscis monkeys, silvered langurs, lesser adjutant storks, raptors, hornbills, and migratory birds.
Rapid developments near the delta over the years have raised concerns about the long-term conservation of its resident dolphins and the need to protect them from being threatened by human activities.
Surprisingly, Irrawaddy dolphins still thrive in the delta, particularly near the Rajang mangroves, which provide them with protection and food.
In these parts of the mangrove system, the water is calmer and clearer, making it an ideal habitat for Irrawaddy dolphins.
According to WWF-Malaysia’s mangrove and dolphin conservation senior officer, Vivien Yeo, mangroves act as nurseries and feeding grounds for fish, crabs, and prawns, supporting the local fisheries and livelihoods.
“They also provide firewood used in the production of smoked prawn, a local delicacy known as udang sesar.
“Additionally, mangroves play a vital role in protecting coastal areas from storm surges and erosion while helping combat climate change by serving as carbon sinks,” she said.
Elaborating, Yeo said that mangroves are known for their resilience and remarkable capacity for self-regeneration, bouncing back even after minor disturbances.
However, there have been instances where natural regeneration was impeded by habitat degradation or destruction. In such cases, active replanting efforts become essential to restoring the mangrove ecosystem.
She pointed out that restoring mangroves involves much more than just planting trees.
“Given that mangroves exhibit distinct zonation patterns defined by salinity levels, tidal inundation frequencies, and soil types, the selection of species becomes critical to ensuring their survival in specific site conditions. Hence, careful consideration of these factors is vital to ensuring the success of mangrove restoration endeavours,” she explained.
Threats
According to the study published in the Journal of Malaysian Applied Biology by Bali et al. (2017), there are reasons for concern about the population ecology of the Irrawaddy dolphins in this river system.
Despite laws in Sarawak to protect and conserve this species since 1958, the Irrawaddy dolphin’s population size, ecology, abundance, and threats to their population have been poorly studied and monitored due to a lack of funding and experts.
In a rapid survey conducted by WWF-Malaysia in 2015, it was noted that the dolphins co-exist well with humans, but this also exposes them to human-animal conflicts.
The communities here are predominantly fishermen. Sometimes, these mammals are accidentally caught and drown when they get entangled in fishing nets.
Additionally, human activities upstream have detrimental impacts on dolphins.
Floating plastic bags, indiscriminately thrown into the river or sea, are dangerous to the dolphins, as they might mistake them for food.
Pollution and contaminant run-off from land can also affect the food chain, leading to the depletion of food sources such as fish, crustaceans, and cephalopods, which the dolphins feed on.
Developmental activities in the coastal region and delta area may impact the long-term survival of dolphins, making them even more threatened.
We should not ignore these threats that could one day wipe out the population of Irrawaddy dolphins from our waters. Together with the government of Sarawak, local planning authorities, government agencies, institutions, local communities, and the public, let’s protect dolphins and their habitats.
For instance, this species has been regarded as “functionally extinct” in Laos. Our dolphins could face the same fate if no holistic conservation action is taken.
Actions taken by the WWF
Working with communities:
With the support of partners and experts, WWF-Malaysia has provided workshops and training to local communities on dolphin and mangrove awareness, mitigation measures for incidental dolphin catch or stranding, and mangrove planting and restoration. Additionally, WWF-Malaysia has empowered local communities to establish a Community Participatory Committee equipped with the relevant skills to manage all these initiatives.
Conducting research:
WWF-Malaysia is collaborating with the Sarawak Forestry Corporation and the Institute of Biodiversity and Environmental Conservation at Universiti Malaysia Sarawak to study the dolphin population and distribution, as well as to determine the incidental catch rate.
So, in conjunction with today’s World Oceans Day, let us all play our part to protect our dolphins and their habitat, the Rajang mangroves.
Your small act of not throwing and leaving plastic trash on the beach has a big impact on millions of marine creatures.
Remember, actions always speak louder than words, and with one small gesture, we can change a life!
