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

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

Informing dugong conservation at several spatial and temporal scales in New Caledonia

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 130,000km 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. The goal of my thesis was to build an evidence-base to enhance the conservation and management of dugongs in New Caledonia at several spatial and temporal scales and enhance understanding of dugong ecology in tropical coral reef environments by: 1. Assessing the temporal changes in the dugong population size and the capacity of the current marine protected areas (MPAs) to protect dugongs at the scale of New Caledonia. 2. Investigating the spatial ecology of dugongs in the coral reef lagoons of New Caledonia by studying their movement patterns and habitat use at local scales. 3. Integrating scientific research conducted on dugongs as part of this thesis to inform decisions relating to dugong conservation and management regionally and internationally. A single baseline aerial survey of dugongs in New Caledonia in 2003 estimated a population of 2026 (± SE = 553) individuals. A second similar survey in 2008 produced a lower estimate of 606 (± SE = 200) individuals, leading to concerns that the dugong population was experiencing a decline. I conducted four additional surveys in 2011 and 2012 with the objectives of updating information on the current size of the dugong population in New Caledonia and investigating evidence of decline in the population. The abundance estimates obtained from my four surveys ranged from 649 (± SE = 195) to 1227 (± SE = 296) dugongs. These results were not significantly different to the 2008 estimate but were significantly lower than the 2003 estimate. I concluded that the confounding effects of variation in environmental conditions, animal behaviour and sampling biases likely played a key role in the variation of the dugong population size estimates as I could not find any evidence external to the surveys that the dugong population had declined between 2003 and 2008 or that temporary migration was likely to have occurred. I used the data obtained from the time series of aerial surveys to develop a spatially-explicit model of dugong distribution and relative density. This model enabled me to determine the distribution of dugongs at the scale of the main island of New Caledonia over nearly a decade of monitoring, and to detect key dugong habitats. Dugongs were not explicitly considered in the design of the network of marine protected areas (MPAs) in New Caledonia. Thus any representation of important dugong areas in the MPA network is incidental. I used the spatially-explicit model of dugong distribution and relative density to retrospectively assess the capacity of the New Caledonia MPA network to protect dugongs from anthropogenic hazards. I quantified the amount of overlap between dugong relative density units and each type of MPA that was managed at the time of the study. I found that most of the important dugong areas in New Caledonia had a low coverage from the MPAs that provide high levels of restriction of anthropogenic activities. I identified several important dugong areas along the west and the north-east coast that were not covered by MPAs and should be considered in future conservation and management plans. The spatial mismatch between MPAs and dugong distribution was likely caused by weaknesses in the planning process. I provided guidance on how these shortcomings can be overcome for marine species of conservation concern in New Caledonia and other regions. The lack of consideration of marine mammals in conservation tools such as MPAs often stems from their highly mobile nature and dynamic movement patterns and the difficulty of defining their specific habitat needs due to lack of knowledge. Information on the dugong's use of space among key habitats and the scale of these movements has been comprehensively studied only in Australian waters where the environment differs from the lagoons of New Caledonia. I used satellite tracking technology to document the use of space by dugongs in the lagoons of New Caledonia. I developed a method of safely and quickly capturing dugongs in coral reef habitats and satellite–tracked 12 adult dugongs in three different regions of the west coast of New Caledonia. Animals displayed individualistic movement patterns. Their extent of movement was large relative to the size of the main island, and some individuals crossed jurisdictional boundaries. Three dugongs exited the lagoon and used the fore reef shelf (i.e., flattened coral reef area, located between the fore reef crest and deep open ocean waters) as corridor to transit from one bay to another. All tracked dugongs returned to their capture location. Home-range analyses showed that the range and core areas used by dugongs reflected the width of the lagoons. The home-range and core areas of dugongs did not differ between day and night. I investigated the habitat use of dugongs at a local scale at Cap Goulvain to enhance understanding of seasonal changes in abundance and habitat use of dugongs in coral reef environments and to provide spatially-explicit data to help local conservation decisions in a key dugong conservation value area. Access to seagrass resources is restricted by tides and the geomorphology of habitats and small size of the lagoon restrict dugongs' space use. I used data obtained from fine-scale dedicated dugong aerial surveys conducted every two weeks over 18 months at low and high tide to determine the seasonal and tidal changes in the number of dugongs and their use of a range of habitats in Cap Goulvain. I then compared the resultant dataset with the temporal changes in water temperature inside and outside the lagoon in this region. I found that more dugongs were sighted during the cool season than during the warm season in Cap Goulvain. At high tide, dugongs were expectedly sighted over the intertidal seagrass meadows in higher proportion than in any other monitored habitats during both seasons. As tides restricted access to the intertidal seagrass meadows there was a seasonal change in the use of other non-seagrass coral reef habitats: during the cool season, a higher proportion of dugongs was sighted outside the lagoon on the fore reef shelf than in any other habitat inside the lagoon; during the warm season the use of the fore reef shelf was less pronounced and dugongs were sighted in higher proportion inside the lagoon in the channels surrounding the intertidal seagrasses. Behavioural thermoregulation is a plausible explanation for the changes in the number of dugongs and the use of the fore reef shelf in Cap Goulvain during the cool season. Further investigation is required to assess the effect of other external factors including the temporal changes in the availability and quality of seagrass and abundance of sharks. Dugong aggregations (i.e., group of ≥ 10 animals) were observed inside the lagoon of Cap Goulvain during the warm season and outside the lagoon during the cool season. I used aerial and underwater footage of the dugong herds located outside the lagoon to explore the behaviour of dugongs in the herds. I found that the dugongs forming the aggregations were resting and no social behaviour other than calves feeding from their mother's teats was identified. The likely causes of dugong aggregations in this habitat include access to warm water, the number of dugongs present in the region at the time, the size of the fore reef shelf, the distance to inshore seagrass resources, and the risk of predation from sharks. These results demonstrated that both seagrass and non-seagrass habitats are important for dugongs and need to be included in future conservation and management programs in New Caledonia as well as other tropical coral reef regions. My thesis provided opportunities to enhance the conservation and management of dugongs in New Caledonia and new insights into the spatial ecology of dugongs in coral reef environments. Future management would be enhanced by considering the important dugong habitats and corridors identified in my research and should be coordinated at an ecological scale relevant to the dugong to be effective. Given the high cultural value of the dugong to the peoples of New Caledonia, communities should be consulted about their desire to participate in community-based management. In addition, ongoing education and communication programs should be continued especially in regions where illegal hunting may occur. Future research should be directed at understanding why illegal hunting occurs in New Caledonia and how compliance with the law could be increased. Further investigating the fine-scale interaction between seagrasses and dugongs in New Caledonia would also greatly enhance our understanding of dugong and seagrass ecology in tropical lagoons and coral reefs more generically