IRRAWADDY DOLPHINS IN THE BAY OF BRUNEI Saifullah A. JAAMAN1*, Nurul Hidayah ABDUL RAHIM1, Azzakirat ABDUL RAMAN1, Bohari ABDULLAH2 ,Nurlisa AZIZUL1, James BALI3, Farah Dayana HAJI ISMAIL1, Toloy KERIPIN MUNSANG3, Anisul Islam MAHMUD4, Mohd Vol MOMIN2 Azmi Marzuki MUDA1, Hairul Masrini MUHAMAD5, Felicita SCAPINI4 & Xuelei ZHANG6 1Institute of Oceanography & Environment (INOS), Universiti Malaysia Terengganu (UMT), 21030 Kuala Nerus, Terengganu, Malaysia. 2 Sakam Enterprise, Unit 17C, 2nd Floor, Bgn. Ben Kassim & Hjh Zaliha, Spg 440, Kg. Sungai Tilong, Jalan Muara BC3315, Brunei Darussalam. 3SARAWAK FORESTRY Corporation Sdn. Bhd., Lot 218, KCLD, Jalan Tapang, Kota Sentosa, 93250 Kuching, Malaysia. 4Le Département de Biologie des Organismes (DBO), Université Libre de Bruxelles, (ULB), Franklin Roosevelt laan 50, 1050 Brussels, Belgium. 5Key Laboratory of Underwater Acoustics & Marine Information Technology, Department of Applied Marine Physics & Engineering, College of Ocean and Earth, Xiamen University, China. 6Marine Ecology Research Center, First Institute of Oceanography (FIO), State Oceanic Administration (SOA), Qingdao 266061, China. *Corresponding author: [email protected] Introduction • Irrawaddy dolphin is the most common inshore cetacean species sighted in large estuaries and bays of East Malaysia and Borneo (Jaaman, 2008; 2010; Minton et al., 2011; Jamal-Hisne et al., 2013) • Its habitat overlap with areas of intensive use by human activities, e.g. fishing, water traffic • Its population and habitat threaten - • By-catch in fisheries – gillnetting, trawling • Coastal development – habitat loss and degradation • Declining fishery resources • Increasing water traffic – accident, noise • Population and behavioural knowledge – vital aspect of the dolphin ecology and an indispensable component in the management of MES populations Irrawaddy dolphins sighted in the Bay of Brunei. • A deep bay and sheltered from the South China Sea conditions. • A natural sea port for the maritime and petroleum industries. • Extensive artisanal fishing and commercial trawling operate throughout the year. Why is the Bay of Brunei IMPORTANT? • Since 2004, research and monitoring of the marine mammals and sea turtles (Marine Endangered Species – MES) and their habitats were conducted in the Malaysian side. • Collaborators: UMT, UMS, Sarawak Forestry Corporation (SFC), Labuan Marine Parks & Bruneian friends (SAKAM Conservation Program). • A unique and special marine ecosystem – mangrove forests, seagrass beds, coral reefs, large estuaries, mudflats and continental slope…..esp. in Lawas, Sarawak. • High diversity of fauna and flora. • Important nursery, feeding and transient ground for dugongs, turtles, dolphins, commercial fishes/shrimps, and seabirds. Why choose BAY OF BRUNEI?? Consist of unique marine Large estuaries of Kuala ecosystems Lawas and Kg. Awat- • Mangrove forest Awat • Large estuaries • Seagrass beds • Mudflats Seagrass at Bukit Sari, Kuala Lawas Mudflat Kuala Lawas BB is less exploited BB & MES face multiple stressors: climate change pollution, land reclaimation, ship navigation, fishing High diversity of fauna and flora. Important nursery, feeding and transient ground for dugongs, turtles, dolphins, commercial fishes/shrimps, and seabirds. High fisheries productivity Mangrove-rich ecosystem • A natural sea port for the maritime and petroleum industries. Labuan Island Ferry and speed boat services at Menumbok, Sabah PETRONAS petroleum refinery 9 center METHODOLOGY Brunei Bay Semi enclosed body of water shared by: • Sabah • Sarawak • Malaysian Federal Territory of Labuan Study site – Bay of Brunei (N5 05.517, E115 19.300) • Brunei Darussalam Boat Survey Effort • Started from April 2013 (HICOE UMT) • Extended in Jan 2015 (FIO-UMT) and continues till Oct 2018 Brunei Bay • Cover all coastal waters • During Northeast (Jan), Pre- Southwest (Apr), Southwest (July) and Pre-Northeast (Oct) monsoon seasons Planned routes for Brunei Bay boat survey Survey route planning RESULTS The Bay of Brunei Malaysia and Brunei Darussalam Map of survey tracks and sighting of Irrawaddy dolphin in the Bay of Brunei (January 2013 – October 2018) • Total number of Irrawaddy dolphin sightings = 145 • Total distance = 4,395.0 km • • Total hours = 308.97 hours • Total survey effort = 50,059.57 kmh Legend Boat track line Irrawaddy dolphin OVERALL EFFORT BY REGION (Brunei and Malaysia) Sighting Day Time Survey Effort No of Region Distance (km) rate (100 Surveyed (hour) (kmh) Sighting km.hrs) Labuan 15 965.20 69.81 5,156.05 8 0.16 Weston 40 2,639.60 207.13 13,611.25 16 0.12 Lawas 61 3,441.60 245.39 15,447.42 57 0.37 Brunei 44 2,998.80 228.46 15,844.86 64 0.40 TOTAL 160 10,045.20 750.79 50,059.57 145 0.29 Table 1.1 Overall boat survey effort and sighting rate of Irrawaddy dolphins in the Bay of Brunei between April 2013 and October 2018 by region. 18000 0.45 16000 0.40 14000 0.35 12000 64 0.30 10000 16 0.25 8000 57 0.20 6000 0.15 4000 0.10 Survey Effort (kmh) Effort Survey 8 2000 0.05 (100km.hrs.) Rate Sighting 0 0.00 Labuan Weston Lawas Brunei Region Survey Effort(kmh) Sighting rate (100 km.hrs) Figure 1.1 : Survey effort and sighting rate of Irrawaddy dolphins observed at different region of the Bay of Brunei. Occurrence by region: (휒2 = 27.64, df = 3, p < 0.01) Highly significant difference; p= 4.32x10-06 Num. of sighting between region. OVERALL EFFORT BY MONSOON SEASON (Brunei and Malaysia) Survey Sighting Day Distance Time No of Season Effort rate (100 Surveyed (km) (hour) Sighting (kmh) km.hrs) JAN (NE) 43 2,606.50 209.38 13,461.09 31 0.23 APRIL (Pre-SW) 38 2,326.20 160.65 10,802.06 40 0.37 JULY (SW) 42 2,648.80 195.41 13,100.54 42 0.32 OCT (Pre-NE) 37 2,463.70 185.35 12,695.88 32 0.25 TOTAL 160 10,045.20 750.79 50,059.57 145 0.29 Table 1.2 Overall boat survey effort and sighting rate of Irrawaddy dolphins in the Bay of Brunei between April 2013 and October 2018 by monsoon seasons. 18000 0.45 16000 0.40 14000 0.35 12000 0.30 10000 0.25 8000 0.20 6000 42 32 0.15 4000 31 40 0.10 Survey Effort (kmh) Effort Survey 2000 0.05 0 0.00 JAN (NE) APRIL (Pre-SW) JULY (SW) OCT (Pre-NE) (100 km.hrs.) Rate Sighting Monsoon season Survey Effort (kmh) Sighting rate (100 km.hrs) Figure 1.2 Survey effort and sighting rate of Irrawaddy dolphins observed during monsoons in the Bay of Brunei Occurrence by season: (휒2= 5.12 , df = 3, p > 0.05) No significant difference; p= 0.16351 Num. of sighting between season OVERALL GROUP SIZE BY REGION (Brunei and Malaysia) Num. of groups with Num. of Sighting Rate calf REGION Group size sighting (% of (per 100 (% of total number of total) km.hrs) sighting) Mean SD Median Range LABUAN 8(6%) 0.16 3(2%) 5.00 5.83 3.50 1 to 19 WESTON 16(11%) 0.12 4 (3%) 8.46 7.02 7.00 1 to 21 LAWAS 57(39%) 0.37 31 (21%) 8.77 7.26 7.00 1 to 35 BRUNEI 64(44%) 0.40 14 (10%) 4.13 3.26 3.00 1 to 15 TOTAL 145 0.29 52 (36%) 6.36 6.02 4.00 1 to 35 Table 1.3 Overall group size of Irrawaddy dolphins in the Bay of Brunei between April 2013 and October 2018 by regions. significantly difference; Kruskal-Walis: H= 16.604, df = 3, p=0.001 group size between region Post-hoc analysis (Mann-Whitney test): U=1044.000, p-val=0.000; there is a difference around Lawas and Brunei OVERALL GROUP SIZE BY REGION (Brunei and Malaysia) 50.00 10 45.00 9 • Group size ranges between 1 to 35 40.00 8 individuals. • Out of 145 sightings of Irrawaddy 35.00 7 dolphins, 30.00 6 • 52 (36%) occurrences of calves in 25.00 5 the group ranges between 1 to 4 20.00 4 individual 15.00 3 10.00 2 • Highest mean of total individuals Num. of sighting total) of(% of sighting Num. 5.00 1 per group was found in Lawas 0.00 0 (8.77, SD=7.26) Labuan Weston Lawas Brunei Region • The biggest group size of Irrawaddy dolphins (35 individuals) was also Num. of sighting (% of total) discovered in the area. Figure 1.3 Percentage of number of sighting of Irrawaddy dolphins in four different regions. OVERALL GROUP SIZE BY MONSOON SEASON (Brunei and Malaysia) Num. of Group size Sighting Num. of groups with calf sighting Species Rate (per (% of total number of (% of 100 km.hrs) sighting) Mean SD Median Range total) JAN (NE) 31(21%) 0.23 17(12%) 8.52 7.67 7.00 1 to 35 APRIL (Pre-SW) 40(28%) 0.37 15(10%) 6.20 5.00 4.50 1 to 18 JULY (SW) 42(29%) 0.32 12(8%) 5.38 5.36 3.50 1 to 25 OCT (Pre-NE) 32(22%) 0.25 8(6%) 5.72 5.99 3.00 1 to 25 TOTAL 145 0.29 52(36%) 6.36 6.02 4.00 1 to 35 Table 1.4 Overall group size of Irrawaddy dolphins in the Bay of Brunei between April 2013 and October 2018 by monsoon seasons. Kruskal-Wallis: H = 5.6740, df = 3, p=0.129 No significant difference; group size between monsoon season OVERALL GROUP SIZE BY MONSOON SEASON (Brunei and Malaysia) 35 9 8 30 7 • Highest mean of total 25 6 individuals per group was 20 5 found during Northeast 15 4 3 monsoon (8.52, SD=7.67) 10 2 Number of sighting Numberof sighting total) (%of 5 1 • The biggest group size of 0 0 JAN (NE) APRIL (Pre-SW) JULY (SW) OCT (Pre-NE) Irrawaddy dolphins (35 individuals) was also Season Num.