Population ecology of irrawaddy dolphin (orcaella brevirostris) in Rajang and Saribas Rivers, Sarawak, Malaysia

James Anak Bali, (2016) Population ecology of irrawaddy dolphin (orcaella brevirostris) in Rajang and Saribas Rivers, Sarawak, Malaysia. Masters thesis, Universiti Malaysia Sabah.

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Abstract

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.

Item Type: Thesis (Masters)
Uncontrolled Keywords: spatial, temporal occurrence, distribution, density, abundance patterns, environmental water parameters
Subjects: Q Science > QL Zoology
Divisions: SCHOOL > Borneo Marine Research Institute
Depositing User: Munira
Date Deposited: 20 Nov 2017 02:15
Last Modified: 20 Nov 2017 02:15
URI: http://eprints.ums.edu.my/id/eprint/16856

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