Dugong distribution and abundance in the Gulf of Carpentaria, Northern Territory: October 2019
Details:
Title
Dugong distribution and abundance in the Gulf of Carpentaria, Northern Territory: October 2019,
Creator
Griffiths, A. D,
Groom, R. A,
Dunshea, G,
Collection
E-Publications,
E-Books,
PublicationNT,
Date
2020-09,
Location
Gulf of Carpentaria,
Description
The Gulf of Carpentaria contains the largest population of dugong in the Northern Territory and the population is also nationally and globally significant. The Northern Territory Government, in collaboration with partners, has been conducting dugong aerial surveys since 1984. This report presents the results of the most recent survey of the Northern Territory’s Gulf of Carpentaria, conducted in October 2019, and compares these results with previous surveys.
The survey used a standardised aerial survey strip transect design. The survey covered 13,534km2 and sampling intensity was approximately 8% of the survey area. The data were used to estimate population size using the Pollock method, which accounts for biases in perception and availability of dugong caused by environmental conditions (i.e., water clarity and sea state) and differences among observers. In addition, we used location specific availability probability estimates to calculate population size, known as the Hagihara method, to improve the accuracy of the dugong aerial survey. The availability probability estimates were recently developed using dugong telemetry data and an experimental observation study for the Gulf of Carpentaria. -- Executive Summary,
Notes
Made available by via Publications (Legal Deposit) Act 2004 (NT).,
Table of contents
Executive summary -- Introduction -- 1.1. Background -- 1.2. Objective -- 2. Methods -- 2.1. Study area -- 2.2. Study design -- 2.3. Data analyses -- 2.3.1. Availability detection probability -- 2.3.2. Perception bias -- 2.3.3. Abundance estimation -- 2.3.4. Temporal variation in abundance and proportion of groups with calves -- 3. Results -- 3.1. Environmental conditions -- 3.2. Perception and availability bias -- 3.3. Dugong sightings -- 3.4. Population size estimates -- 3.5. Temporal and spatial variation in abundance and calf proportions -- 3.5.1. Abundance -- 3.5.2. Proportion of groups with calves -- 3.6. Observations of other marine fauna -- 4. Discussion -- 5. Acknowledgements -- 6. References -- Appendices -- Appendix 1. Comparison of dugong population estimates in 2007, 2014 and 2019 based in the Pollock et al. (2006) method -- Appendix 2. Location maps of sighting data for the 2019 aerial survey -- Figures and Tables,