Population ecology of irrawaddy dolphin (orcaella brevirostris) in Rajang and Saribas Rivers, Sarawak, Malaysia
The Irrawaddy dolphin (Orcaella brevirostris) is the most common cetacean species inhabiting the coastal waters of the main estuaries of Sarawak. Their habitats are highly overlapping with the areas of intensive use by human activities, which have evolved potential threats to their very survival....
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| Format: | Thesis |
| Language: | English |
| Published: |
2016
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| Subjects: | |
| Online Access: | https://eprints.ums.edu.my/id/eprint/16856/1/Population%20ecology%20of%20irrawaddy.pdf |
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| Summary: | The Irrawaddy dolphin (Orcaella brevirostris) is the most common cetacean species
inhabiting the coastal waters of the main estuaries of Sarawak. Their habitats are
highly overlapping with the areas of intensive use by human activities, which have
evolved potential threats to their very survival. The study was conducted in Rajang
and Saribas rivers, Sarawak with the objectives to determine their spatial and
temporal occurrence and distribution, density and abundance patterns, their
association with environmental water parameters, and to identify their 'hot spot' area.
Data collection was carried out from April 2009 to October 2010. Surveys were
conducted using modified boat strip-transect technique, with the width of the river
as the strip width for each transects and each river was divided into segments.
Irrawaddy dolphins were found in all segments of both Rajang and Saribas rivers but
they were not distributed evenly. Higher mean sighting frequency, mean number of
individual Sighted per survey, sighting rate, probability of sighting, density and
abundance of Irrawaddy dolphins were recorded at the lower river segment of Rajang
and Saribas rivers. Probability of sighting was highly significant between the Kuala
Rajang-Sarikei and Sarikei-Sibu segments (McNemar: χ²) =38.726, df=1, p=0.000).
Probability of sighting was highly significant between the Kuala Sari bas and and Pusa Sebemban
segments in Saribas River (McNemar: χ² =37.770, df=l, p=0.000). The
density (Mann-Whitney: U=28.0, n=9 and 7, p=0.758) and abundance (Mann Whitney:
U=24.0, n= 9 and 7, p=0.470) of animals between the river segments in
Rajang River are not statistically different. There is no statistically significicant
different on density (Mann-Whitney: U=24.0, n=12 and 8, p=0.069) and abundance
(Mann-Whitney: U=23.0, n=12 and 8, p=0.57) of animals between the river
segments in Saribas River. The probability of sighting between the seasons in both
Rajang and Saribas rivers was not statistical Significant difference. The abundance of
O. brevirostriswas not statistically different between seasons for both in Rajang River
(Kruskall-Wallis: H=2.768, df=2, p=0.251) and Saribas River (Kruskall-Wallis:
H=0.323, df=2, p=0.851). Distribution of O. brevirostris in Rajang River is
significantly associated with salinity with weak correlation, while in Saribas River their
distribution is significantly associated with turbidity, surface water temperature and
salinity with water temperature has strong negative correlation. The 'hot spot' of O.
brevirostris in Rajang River was identified between Sungai Sebubal to Sungai Sarong
while in Saribas River, the area is situated between the waters of Kampung SepinangKampung
Beladin Hilir. The conservation and protection of O. brevirostris and their
habitats in the two river systems need to be managed holistictically with specific
recommendations on conservation education to raise public awareness about the
importance of protecting the new identified 'hot spot' areas, developed the the newly
identified 'hot spots' as new eco-tourism tousim site for dolphin watching and
continue carry out more detail researches to overcome the knowledge gaps that
required to produce a 'Species Conservation Management Plan' for O. brevirostris in
these areas. |
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