MATERIALS AND METHODS

Data on which this report is based were gathered through boat, aerial and interview surveys, and site investigations on stranded or trapped dugongs reported from the coast of Sabah and Sarawak in between 1996 and 2001.

The systematic line-transect method developed for marine mammals in developing countries (following Wade and Gerrodette 1993; and modified by Aragones et al. 1997 and Dolar et al. 1997) was used in boat surveys. Area covered including the Exclusive Economic Zone (EEZ), bays, and several main rivers upstream, to between 1 to 5 nautical miles. Two types of boat were used: (1) a 13 meter research vessel UMS GALAXEA and (2) using a 5.2 meter fiberglass boat powered by two 75HP outboard engines. Surveys were conducted only during daytime in sea state conditions of Beaufort 0 - 4. Throughout the surveys, the speed of the boats was maintained between 12 to 15 knots and navigational data (time, GPS position, compass course, Beaufort scale, and presence/absence of rain) were recorded every 15 - 20 minutes and at course changes. At least three trained observers and one survey leader (also acted as data recorder, navigator and a person collecting oceanographic and meteorological data) were involved in each survey trip. An observation platform, about 3 m above sea level, fitted on the boat has provided 360 degree unobstructed viewing of the surrounding ocean. Observers searched for dugongs using naked eyes and also with the aid of FUJINON 7 X 50 magnifier binoculars.

Between March 1997 and November 2000, 12 boat surveys of marine mammals were carried out in Sabah. A total of 65 days was spent at sea with 316 hours 6 minutes of survey efforts, covering an approximately 3,923 nm of survey track. While in Sarawak, only one boat survey was carried out from 12 May - 2 June 2001 with 14 survey days and 7 rest days due to bad weather. An approximately 1,029.8 nm of survey track was covered with 78 hours and 15 minutes of survey efforts.

Aerial surveys conformed to the procedure established by Aragones et al. (1997) with respect to speed, altitude, and recording of data, except that the only aircraft available for the Sabah and Sarawak flights was a Cessna 172, single engine, high wing, four-passenger aircraft belonging to the Sabah Flying Club. A series of predetermined locations marking the beginning and end of each transect was entered into the aircraft’s GPS to give the pilot a course to follow. Except in Brunei, Kimanis, and Labuk Bays, where transect lines were relatively zigzagged, other transect-lines in Sabah were relatively parallel to the coast and at a distance of between 2 to 5 nm from shore. In Sarawak, the aircraft flew over predetermined tracklines covering the EEZ waters with maximum distance of 60nm offshore. The survey team consisted of the pilot, a front-right survey leader, and two rear-seat observers. They searched for marine mammals using naked eyes and also with the aid of FUJINON 7 X 50 magnifier binoculars.

An aerial survey of marine mammals was carried out on May 2000 in Sabah and on April 2001 in Sarawak, respectively. The total day, distance and hour surveyed by aircraft in Sabah was 7 days, 1,574 nm and 20 hours 27 minutes, while in Sarawak was 13 days, 2,919.06 nm and 36 hours 48 minutes.

Interview survey procedures and distribution of questionnaire survey forms (following Aragones et al. 1997; Dolar 1994; Dolar et al. 1994) were used to determine the magnitude of dugong hunting and incidental catches in fisheries, and estimate level of mortality. Interviews were conducted during visits to fishing villages, fish markets, fish landing jetties and onboard fishing boats during anchorage. During site visits, village headmen, fishermen and other knowledgeable locals were assembled into groups and asked questions pertaining to their fishing efforts and dugong sightings, strandings, hunting and / or incidental catches, and their beliefs and myths toward the animals. Beside that, questionnaires and marine mammal posters were distributed to fishermen, officer-in-charge of the Department of Wildlife, Fisheries and Sabah Parks offices in the districts, school teachers and marine tour/dive operators. Throughout the survey, 149 groups of people were interviewed in Sabah and 84 groups of people were interviewed in Sarawak, respectively.

In addition, stranded dugongs, including animals caught in fisheries and hunting, that were reported from many areas in Sabah were examined and photographed where possible. Referring to Yaptinchay (1996a), dead dugongs were measured, sexed and identified to species level. Date, location, and circumstance of stranding were noted and all information gathered was recorded in datasheets for stranding.