A Method for Capturing Dugongs (Dugong dugon) in Open Water (original) (raw)
Related papers
Physiological Response of Wild Dugongs (Dugong dugon) to Out-of-Water Sampling for Health Assessment
Aquatic Mammals, 2010
The dugong (Dugong dugon) is a vulnerable marine mammal with large populations living in urban Queensland waters. A mark-recapture program for wild dugongs has been ongoing in southern Queensland since 2001. This program has involved capture and in-water sampling of more than 700 dugongs where animals have been held at the water surface for 5 min to be gene-tagged, measured, and biopsied. In 2008, this program expanded to examine more comprehensively body condition, reproductive status, and the health of wild dugongs in Moreton Bay. Using Sea World's research vessel, captured dugongs were lifted onto a boat and sampled out-of-water to obtain accurate body weights and morphometrics, collect blood and urine samples for baseline health parameters and hormone profiles, and ultrasound females for pregnancy status. In all, 30 dugongs, including two pregnant females, were sampled over 10 d and restrained on deck for up to 55 min each while biological data were collected. Each of the dugongs had their basic temperature-heart rate-respiration (THR) monitored throughout their period of handling, following protocols developed for the West Indian manatee (Trichechus manatus). This paper reports on the physiological response of captured dugongs during this out-of-water operation as indicated by their vital signs and the suitability of the manatee monitoring protocols to this related sirenian species. A recommendation is made that the range of vital signs of these wild dugongs be used as benchmark criteria of normal parameters for other studies that intend to sample dugongs out-of-water.
Aerial surveys coupled with incidental sightings and interviews provided information to detect trends in the relative abundance and spatial distribution of dugongs in Palau. Twenty adults and 10 calves of Dugong dugon were counted during 3 aerial surveys September and November of 2007 representing a density of 1.0 dugongs/20km2. Aerial surveys in Palau in the past two decades have differed in the types of aircraft used, level of expertise, number of observers, weather conditions, track paths, and temporal variations. Given these limitations, a qualitative comparison of aerial surveys indicates a trend towards increased numbers of calves and dugong densities within Malakal Koror. A trend towards an increased rate of sighting (0.166 dugong/min/survey day/ flight hour) was found. The distribution patterns show a tendency towards a shift in abundance from the west coast of Babeldaob to the Malakal area over the past 15 years. The helicopter pilot sighted 12 dugongs in Malakal Area on two occasions during 2007 as incidental sightings, the largest herd reported in Palau in two decades. Three boat surveys in Malakal, Koror, and the West Coast of Babeldaob were conducted during 2007. One dugong was sighted in the Malakal area, no dugongs were observed in Babeldaob. Small populations are a challenge to understand, as observing them in their natural habitats is a rare event. On site interviews with several fishermen in Babeldaob indicated that dugongs were present in the early morning hours. Aerial surveys were more effective than boat surveys, covering more area in less time with more sightings above than at the water surface. An Incidental Sightings Program was initiated in 2007. Forms and two brochures were developed and disseminated to over 30 businesses, government agencies and nongovernment groups. A total of 30 forms were completed and analyzed. Observers reported a total of 49 adults and 9 calves. A total of 40 dugongs were seen by Lighthouse channel near Ngederrak reef in Malakal known feeding habitat for dugongs. Observers saw 35 dugongs in other locations within the southern lagoon of Koror. Six dugongs were seen in Babeldaob for the following States: Ngarchelong (2), Ngardmau (1), Ngatpang (1), Aimeliik (1) and Airai (1). Sightings occurred from 4am to 10pm but most frequently from 8-11am. Most dugongs were observed swimming, two were reported feeding. Dugongs were sighted while observers were on boats with the engine turned off. Dugongs were in the open ocean (32), seagrass beds (11), coral reefs and drop-offs (11) or lagoons and shallow sandy habitats (4). Interviews with five fishermen provide differing views on the status of dugong. Some fishers say that there are more dugongs others say there are less than in the past. Enforcement of existing laws is required. A proposed five year action plan was developed to help sustain a viable dugong population in Palau. Objectives focus on education and public awareness; mitigation of threats to dugongs and their habitats, regular aerial survey, an ongoing incidental sightings program, surveys of seagrass habitats, necropsy workshops and collaboration with partners at the local, regional and international levels.
Wildlife Research, 1990
Techniques were developed for tracking individual dugongs using buoyant, tethered, conventional and satellite radio transmitters, and applied to six dugongs caught off the North Queensland coast. The dugongs (one immature, one pubertal, and four mature males) were caught by bull-dogging or hoop-netting and tracked for between 1 and 16 months. All spent most of their time in the vicinity of inshore seagrass beds using overlapping home ranges (MAP 0.95) of 4 to 23 km2. The only dugong to undertake long-distance movements was the pubertal male, which journeyed between core areas in two bays about 140 km apart three times in 9 weeks, completing the journey in as little as 2 days. One of the adult animals made several journeys of about 10 km up the tidal reaches of a creek. These results support the Great Barrier Reef Marine Park Authority's policy of conserving dugongs by giving a high level of protection to some inshore seagrass beds that support large numbers of animals. The relative merits of conventional and satellite telemetry for tracking dugongs are discussed.
2011
The study aimed to (a) provide record of dugong stranding and mortality, (b) conduct necropsy of dugong, (c) characterize the circumstantial causes of mortality and stranding and (d) determine the threats that impede dugong conservation.Secondary data available on strandings and mortality of dugong were utilized to confirm validity of data obtained from interview of fishfarmers. Record of logged and reported incidents of dugong strandings and mortality were also retrieved. Necropsy was done every time dugong mortality occurred. Information and data were kept in dugong data sheets. Preliminary results showed that from 2001 – 2008, six strandings of dugongs have been documented in Malita, Davao del Sur. All the six strandings occurred within an approximate 10 km stretch of coastline (from Brgy. Lacaron to Brgy. Tingolo) of Malita, Davao del Sur. One out of the six strandings was a female baby dugong. The other four were male adult dugong with a length of not less than 2m. The probable...
Is acoustic tracking appropriate for air-breathing marine animals? Dugongs as a case study
Journal of Experimental Marine Biology and Ecology, 2015
Marine animals face increased pressure through expanded shipping and recreational activities. Effective conservation and management of large species like marine mammals or sea turtles depend on knowledge of movement and habitat use. Previous studies have used data collected from either satellite or acoustic telemetry but rarely both. In this study, data from satellite and acoustic technologies were used to: determine the efficacy of satellite and acoustic telemetry to define dugong movement patterns; compare the benefits and limitations of each approach; examine the costs of each approach in relation to the amount and type of data provided; and relate telemetry data to the boundaries of a Go Slow area designed to protect dugongs and turtles from vessel strike within an urbanised coastal embayment (Moreton Bay, Queensland, Australia). Twenty-one dugongs were captured in seagrass habitats on the Eastern Banks of Moreton Bay in July-September 2012 and July 2013 and fitted with GPS and acoustic transmitters. Both satellite and acoustic telemetry produced reliable presence and movement data for individual dugongs. When the dugongs were within the range of the acoustic array, there was relatively good correspondence between the overall space use measures derived from GPS and acoustic transmitters, demonstrating that acoustic tracking is a potentially valuable and cost-effective tool for monitoring local dugong habitat use in environments equipped with acoustic receiver arrays. Acoustic technology may be particularly useful for species that establish home ranges with stable residency especially near large urban or port environs. However, the relative merits of the two technologies depend on the research question in the context of the species of interest, the location of the study and whether the study site has an established acoustic array.
2012
Distribution pattern of dugongs is a key component for space-based managements. Vocal interaction of dugongs may result in a distinctive distribution pattern. This study described the distribution patterns of vocalising dugongs, solitary and cow-calf pairs of dugongs. Total of 31 hours and 24 minutes of aerial surveys over southern Thai waters were conducted to observe distribution of the dugongs in 2006, 2008 and 2010. We also conducted towed acoustic surveys to observe the distribution of vocalising dugongs. Total of 473 adult dugongs and 122 calves and 223 vocalizations were found. The distribution of vocalising dugongs was clumped with the range of about 1 km 2 . Groups with cow-calf pairs (9 animals on average) were also clumped. Their distribution range was about 3 km 2 and did not overlap that of vocalising dugongs. Average number of individuals in groups without cow-calf pairs was about 1, indicating that the most of the group members were solitary. They distributed widely t...