An inventory of dugong aerial surveys in Australia

• In Australia, the dugong (Dugong dugon) has significant cultural, ecological and conservation value. The species is a Matter of National Environmental Significance and is protected under the EPBC Act as a listed migratory and marine species. • Since the early 1970s various aerial survey methodologies have been used to provide data on the distribution and abundance of the dugong across northern Australia. The survey designs and platforms have evolved through time, and so have the methods to estimate dugong population distribution, sizes and trends. • An inventory of all dugong aerial surveys across the dugong range in Australia has not previously been compiled making it difficult to obtain a clear understanding of the efforts that have been put to date on surveying dugongs across their Australian range. The existence, locality and accessibility of the data generated from those surveys and their associated reports and/or scientifically peer-reviewed publications are not readily located or available for many surveys. • This inventory compiles information from all dugong aerial surveys undertaken since the first use of this methodology for dugongs in Australia, including date of survey, approach undertaken to survey, latest abundance estimate, relevant reference and link to publication, data availability and location etc. It also provides spatially-explicit maps to represent survey effort to date across the entire known dugong range in Australia. The development of this inventory has also helped identify similarities and discrepancies in the way dugong population estimates, trends and spatial distribution models have been generated. • Dugong aerial surveys in Australia date back from the early 1970s with shoreline reconnaissance surveys to assess the presence, distribution and relative numbers of dugongs in the inshore areas around the mainland and islands

Ecoregional and temporal dynamics of dugong habitat use in a complex coral reef lagoon ecosystem

Mobile marine species display complex and nonstationary habitat use patterns that require understanding to design effective management measures. In this study, the spatio-temporal habitat use dynamics of the vulnerable dugong (Dugong dugon) were modelled from 16 satellite-tagged individuals in the coral reef lagoonal ecosystems of New Caledonia, South Pacific. Dugong residence time was calculated along the interpolated tracks (9371 hourly positions) to estimate intensity of use in three contrasting ecoregions, previously identified through hierarchical clustering of lagoon topographic characteristics. Across ecoregions, differences were identified in dugong spatial intensity of use of shallow waters, deeper lagoon waters and the fore-reef shelf outside the barrier reef. Maps of dugong intensity of use were predicted from these ecological relationships and validated with spatial density estimates derived from aerial surveys conducted for population assessment. While high correlation was found between the two datasets, our study extended the spatial patterns of dugong distribution obtained from aerial surveys across the diel cycle, especially in shallow waters preferentially used by dugongs at night/dusk during high tide. This study has important implications for dugong conservation and illustrates the potential benefits of satellite tracking and dynamic habitat use modelling to inform spatial management of elusive and mobile marine mammals

Ecoregional and temporal dynamics of dugong habitat use in a complex coral reef lagoon ecosystem

Mobile marine species display complex and nonstationary habitat use patterns that require understanding to design effective management measures. In this study, the spatio-temporal habitat use dynamics of the vulnerable dugong (Dugong dugon) were modelled from 16 satellite-tagged individuals in the coral reef lagoonal ecosystems of New Caledonia, South Pacific. Dugong residence time was calculated along the interpolated tracks (9371 hourly positions) to estimate intensity of use in three contrasting ecoregions, previously identified through hierarchical clustering of lagoon topographic characteristics. Across ecoregions, differences were identified in dugong spatial intensity of use of shallow waters, deeper lagoon waters and the fore-reef shelf outside the barrier reef. Maps of dugong intensity of use were predicted from these ecological relationships and validated with spatial density estimates derived from aerial surveys conducted for population assessment. While high correlation was found between the two datasets, our study extended the spatial patterns of dugong distribution obtained from aerial surveys across the diel cycle, especially in shallow waters preferentially used by dugongs at night/dusk during high tide. This study has important implications for dugong conservation and illustrates the potential benefits of satellite tracking and dynamic habitat use modelling to inform spatial management of elusive and mobile marine mammals

Conservation du dugong en Nouvelle-Calédonie : une étude à plusieurs échelles spatio-temporelles. Synthèse finale

Comprehensive, up-to-date spatial information on species distributions and threatening processes can enhance the identification of sites for conservation and management action. Such information is often incomplete or simply unavailable at a scale that can inform real-world decision making because the cost and capacity needed for collecting reliable information are high especially when targeting species that occupy large ranges.Obtaining data to inform conservation at the appropriate spatial scale is of particular importance for species that occupy large ranges. The dugong (Dugong dugon) is a seagrass specialist and marine mammal that occurs over 130,000 km of coastline in the Indo-West-Pacific. The dugong attracts global conservation attention because it is listed as vulnerable (IUCN Red List) and is increasingly exposed to multiple anthropogenic hazards in most of its range. There are many regions within the dugong’s range where the likelihood of survival of the species is unknown. Collecting spatial-ecological information on the dugong in these regions can inform and optimize the effectiveness of regional and national conservation and management initiatives.The island-archipelago of New Caledonia is located in the Oceania region at the eastern edge of the dugong’s range. The conservation status of the dugong in this region is unknown. The presence of the charismatic dugong in the lagoons of New Caledonia was an explicit reason for the World Heritage listing of some of the lagoons. No conservation actions have been implemented in New Caledonia to ensure the maintenance of the dugong stock except for the legislation that restricts dugong harvesting despite the species’ high biodiversity, cultural and traditional value.Comprendre l’écologie d’une espèce et les processus qui la menacent peut aider à identifier des sites de conservation afin d’améliorer les mesures de gestion. Ces informations sont souvent incomplètes ou tout simplement indisponibles à une échelle permettant des prises de décisions et la mise en place d’actions de conservation et de gestion efficaces. En effet, le coût et l’effort nécessaires pour recueillir ce type d’information, sont souvent élevés, notamment quand les espèces ciblées occupent de grands espaces.Le dugong (Dugong dugon) est un mammifère marin herbivore qui est présent sur 130 000 km de côtes dans la région de l’Indo-Pacifique. Une attention internationale particulière est portée sur cette espèce inscrite comme ‘vulnérable’ sur la liste rouge de l'UICN. Le dugong est notamment de plus en plus menacé par l’accroissement des activités anthropiques sur la plupart des littoraux dans son aire de répartition. Dans de nombreuses régions, la probabilité de survie et le statut du dugong sont inconnus. La collecte d'informations sur l’écologie du dugong dans ces régions permet d’améliorer l'efficacité des initiatives de conservation et de gestion de l’espèce.L'archipel de Nouvelle-Calédonie, situé dans la région océanienne, se trouve à l'extrémité est de la zone de répartition mondiale du dugong. Le statut de conservation de cette espèce dans cette région est inconnu. La présence de cet animal charismatique dans les lagons de Nouvelle-Calédonie était l’un des critères retenu pour l'inscription de la majeure partie des lagons et récifs de l’archipel au patrimoine mondial de l’UNESCO. Toutefois, au commencement de la présente étude hormis la législation interdisant la chasse du dugong dans une grande partie du territoire, aucune mesure concrète de conservation du dugong n’était en place en Nouvelle-Calédonie pour assurer le maintien de la population.Ce projet avait pour but d'étudier l'écologie des dugongs à différentes échelles spatio-temporelles en Nouvelle-Calédonie et de nourrir la réflexion engagée sur les stratégies de conservation de cette espèce sur le territoire

A Novel Method for Using Small Unoccupied Aerial Vehicles to Survey Wildlife Species and Model Their Density Distribution

There is growing interest from research and conservation groups in the potential for using small unoccupied aerial vehicles (UAVs; <2 kg) to conduct wildlife surveys because they are affordable, easy to use, readily available and reliable. However, limitations such as short flight endurance, and in many situations, aviation regulations, have constrained the use of small UAVs in survey applications. Thus, there is a need to refine survey methods adapted to small UAVs that conform to standard operations within aviation law. We developed a novel survey approach based on a grid sampling design using two multirotor UAVs (Phantom 4 Pros) flying simultaneously, within visual line of sight, from our vessel base-station. We used this approach to assess the fine-scale distribution and abundance of dugongs (Dugong dugon) in the remote waters of the Pilbara, Western Australia during three field seasons across 2 years. We surveyed 64 non-overlapping survey cells in random order one or more times and obtained complete image coverage of each surveyed cell of our 31 km2 survey area. Our sampling design maximizes sampling effort while limiting survey time by surveying four cells, two at a time, from one location. Overall, we conducted 240 flights with up to 17 flights per day (mean = 14 flights per day) and could obtain complete coverage of up to 11.36 km2per day. A total of 149 dugongs were sighted within the 50,482 images which we manually reviewed. Spatially-explicit models of dugong density distribution (corrected for availability and perception bias) were produced using general additive models to identify areas more or less used by dugongs (range of corrected dugong densities across all field season = 0.002–1.79 dugongs per 0.04 km2). Dugong abundance estimates ranged from 47 individuals in June 2019 (CV = 0.17) to 103 individuals in May 2018 (CV = 0.36). Our method, which proved convincing in a real-word application by its feasibility, ease of implementation, and achievable surface coverage has the potential to be used in a wide range of applications from community-based local-scale surveys, to long-term repeated/intensive surveys, and impact assessments and environmental monitoring studies

Reduction of species identification errors in surveys of marine wildlife abundance utilising unoccupied aerial vehicles (UAVs)

The advent of unoccupied aerial vehicles (UAVs) has enhanced our capacity to survey wildlife abundance, yet new protocols are still required for collecting, processing, and analysing image-type observations. This paper presents a methodological approach to produce informative priors on species misidentification probabilities based on independent experiments. We performed focal follows of known dolphin species and distributed our imagery amongst 13 trained observers. Then, we investigated the effects of reviewer-related variables and image attributes on the accuracy of species identification and level of certainty in observations. In addition, we assessed the number of reviewers required to produce reliable identification using an agreement-based framework compared with the majority rule approach. Among-reviewer variation was an important predictor of identification accuracy, regardless of previous experience. Image resolution and sea state exhibited the most pronounced effects on the proportion of correct identifications and the reviewers’ mean level of confidence. Agreement-based identification resulted in substantial data losses but retained a broader range of image resolutions and sea states than the majority rule approach and produced considerably higher accuracy. Our findings suggest a strong dependency on reviewer-related variables and image attributes, which, unless considered, may compromise identification accuracy and produce unreliable estimators of abundance

Reduction of Species Identification Errors in Surveys of Marine Wildlife Abundance Utilising Unoccupied Aerial Vehicles (UAVs)

The advent of unoccupied aerial vehicles (UAVs) has enhanced our capacity to survey wildlife abundance, yet new protocols are still required for collecting, processing, and analysing image-type observations. This paper presents a methodological approach to produce informative priors on species misidentification probabilities based on independent experiments. We performed focal follows of known dolphin species and distributed our imagery amongst 13 trained observers. Then, we investigated the effects of reviewer-related variables and image attributes on the accuracy of species identification and level of certainty in observations. In addition, we assessed the number of reviewers required to produce reliable identification using an agreement-based framework compared with the majority rule approach. Among-reviewer variation was an important predictor of identification accuracy, regardless of previous experience. Image resolution and sea state exhibited the most pronounced effects on the proportion of correct identifications and the reviewers’ mean level of confidence. Agreement-based identification resulted in substantial data losses but retained a broader range of image resolutions and sea states than the majority rule approach and produced considerably higher accuracy. Our findings suggest a strong dependency on reviewer-related variables and image attributes, which, unless considered, may compromise identification accuracy and produce unreliable estimators of abundance

C and N stable isotopes enlighten the trophic behaviour of the dugong (Dugong dugon)

The dugong (Dugong dugon), a large marine mammal herbivore of the Indo-Pacific, is vulnerable to extinction at a global scale due to a combination of human-related threats including habitat degradation. The species forages on seagrass habitats (marine phanerogams) and plays a key role in the functioning and sensitivity of these declining coastal ecosystems. The trophic behaviour and plasticity of dugong populations in response to extrinsic and intrinsic factors are therefore crucial features to both dugong and seagrass conservation. Yet, this knowledge remains limited to few visual observations and analyses of mouth, stomach or faecal contents of stranded individuals. We take advantage of a long-term monitoring of stranded individuals from the endangered New Caledonian population to depict features of dugongs’ trophic ecology from Carbon and Nitrogen stable isotopes. A total of 59 dugong skin samples were used to portrait the stable isotope niche of dugongs according to their sex and maturity. In light of previous work conducted in New Caledonia, a subset of these samples was used to model the trophic mix of dugong males and females. Our stable isotope mixing models used C and N isotope values of 10 taxa belonging to five divisions of metazoans, plants, and chromists. Our results represent the first estimate of the species dietary niche in the isotopic space. They suggest that the diet of dugong calves overlaps more with that of adult females (δ13C: − 6.38 ± 1.13 ‰; δ15N: 2.49 ± 1.10 ‰) than males (δ13C: − 5.92 ± 1.10 ‰; δ15N: 3.69 ± 1.28 ‰). Further, we highlight differences in the expected trophic mix of dugong adult males and females. From these, we formulate a sex-specific foraging behaviour hypothesis in dugongs, whereby lactating females could forage over smaller spatial ranges but more diverse food sources than males. The study emphasizes the importance of long-term stranding monitoring programs to study the ecology of marine mammals.. Finally, it depicts an ecological feature that may contribute to the sensitivity of vulnerable dugongs to ongoing changes on tropical coastal ecosystems

2022 Dugong Aerial Survey: Mission Beach to Moreton Bay

Project objectives: • Dugongs are of significant biodiversity value as the only extant species in the Family Dugongidae and one of only four species in the Order Sirenia, all of which are listed as vulnerable to extinction by the IUCN. • Australia has international responsibilities for dugong conservation, particularly in the Great Barrier Reef (GBR) region, where the dugong feeding grounds are listed as one of the World Heritage values of the region. • Dugongs have been monitored along the Queensland coast since the 1980s using a series of standardised aerial surveys. These surveys have provided long-term information on the distribution and abundance of dugongs, which has informed management and are a requirement of the Reef 2050 Long-Term Sustainability Plan (Reef 2050 Plan). The surveys have been loosely coordinated across jurisdictions and largely conducted at the same time of year at approximately five-year intervals. The areas adjacent to the Great Barrier Reef have been included to account for temporary migrations of dugongs across jurisdictional boundaries. • This report presents the result of an aerial survey for dugongs and large juvenile and adult marine turtles that was conducted in November-December 2022 in the coastal waters of Queensland from Mission Beach to the Queensland-New South Wales border. The survey is the latest in the time series of surveys conducted by James Cook University-TropWATER researchers since the 1980s. • The objectives of our study were to: 1. continue the time series of surveys for dugongs and large marine turtles. 2. to use the latest programming, modelling, and statistical advances to enhance our dugong distribution and abundance analysis. 3. engage with First Nations people across the surveyed area to: (1) raise awareness about dugong and sea turtle ecology and conservation issues, (2) seek interest from the communities in becoming involved in dugong survey work at different spatial scales, particularly aerial imagery surveys. 4. discuss new avenues for reducing uncertainty in the results for the surveys and the potential of new research tools for dugong monitoring in the future 5. provide advice to relevant management partners (GBRMPA, DCCEEW, and the Queensland Government) and Traditional Owners about the implications of the findings for the conservation, management, and monitoring of dugongs and large marine turtles1 in the southern GBR, Hervey Bay-GSS and Moreton Bay