Many populations of southern hemisphere baleen whales are recovering and are again becoming domin... more Many populations of southern hemisphere baleen whales are recovering and are again becoming dominant consumers in the Southern Ocean. Key to understanding the present and future role of baleen whales in Southern Ocean ecosystems is determining their abundance on foraging grounds. Distance sampling is the standard method for estimating baleen whale abundance but requires specific logistic requirements which are rarely achieved in the remote Southern Ocean. We explore the potential use of tourist vessel-based sampling as a cost-effective solution for conducting distance sampling surveys for baleen whales in the Southern Ocean. We used a dataset of tourist vessel locations from the southwest Atlantic sector of the Southern Ocean and published knowledge from Southern Ocean sighting surveys to determine the number of tourist vessel voyages required for robust abundance estimates. Second, we simulated the abundance and distributions of four baleen whale species for the study area and samp...
Aerial surveys are frequently used to estimate the abundance of marine mammals, but their accurac... more Aerial surveys are frequently used to estimate the abundance of marine mammals, but their accuracy is dependent upon obtaining a measure of the availability of animals to visual detection. Existing methods for characterizing availability have limitations and do not necessarily reflect true availability. Here, we present a method of using small, vessel-launched, multi-rotor Unoccupied Aerial Vehicles (UAVs, or drones) to collect video of dolphins to characterize availability and investigate error surrounding group size estimates. We collected over 20 h of aerial video of dive-surfacing behaviour across 32 encounters with Australian humpback dolphins Sousa sahulensis off northwestern Australia. Mean surfacing and dive periods were 7.85 sec (se = 0.26) and 39.27 sec (se = 1.31) respectively. Dolphin encounters were split into 56 focal follows of consistent group composition to which example approaches to estimating availability were applied. Non-instantaneous availability estimates, assuming a 7 sec observation window, ranged between 0.22 and 0.88, with a mean availability of 0.46 (CV = 0.34). Availability tended to increase with increasing group size. We found a downward bias in group size estimation, with true group size typically one individual more than would have been estimated by a human observer during a standard aerial survey. The variability of availability estimates between focal follows highlights the importance of sampling across a variety of group sizes, compositions and environmental conditions. Through data re-sampling exercises, we explored the influence of sample size on availability estimates and their precision, with results providing an indication of target sample sizes to minimize bias in future research. We show that UAVs can provide an effective and relatively inexpensive method of characterizing dolphin availability with several advantages over existing approaches. The example estimates obtained for humpback dolphins are within the range of values obtained for other shallow-water, small cetaceans, and will directly inform a government-run program of aerial surveys in the region.
An automated algorithm for passive acoustic detection of blue whale D-calls is developed based on... more An automated algorithm for passive acoustic detection of blue whale D-calls is developed based on established deep learning methods for image recognition via the DenseNet architecture. Koogu—an open-source Python package—was used for developing the detector. The detector was trained on annotated acoustic recordings from the Antarctic, and the performance of the detector was assessed by calculating precision and recall using a separate independent dataset also from the Antarctic. Detections from both the human analyst and automated detector were then inspected by a more experienced analyst to identify any calls missed by either approach and to adjudicate whether the apparent false-positive detections from the automated approach were actually true-positives. Lastly, an additional performance assessment was conducted using double-platform methods (via a closed-population Huggins mark recapture model) to assess the probability of detection of both the human analyst and automated detecto...
The Australian Antarctic Division of the Australian Government is planning an Antarctic Blue Whal... more The Australian Antarctic Division of the Australian Government is planning an Antarctic Blue Whale Voyage in the austral summer of 2013. This voyage is a project of the Southern Ocean Research Partnership’s (SORP ) Antarctic Blue Whale P roject. The Antarctic Blue Whale Project aims to develop technologies and collect data that will result in an estimation of the abundance of Antarctic Blue Whales (Balaenoptera musculus intermedia), improve understanding of population structure and linkages between breeding a nd feeding grounds, and characterise the behaviour in the feeding grounds. The 2013 Antarctic Blue Whale Voyage aims to further develop passive acoustic tracking methodologies to increase sighting rates of Antarctic Blue Whales. Individuals identified based on photography identification, genetic biopsies and tagging will contribute to further develop mark-and-recapture methods to meet the aims of the Antarctic Blue Whale Project. The voyage is currently planned to be a minimum ...
ABSTRACT The R package nupoint provides tools for estimating animal density from point transect s... more ABSTRACT The R package nupoint provides tools for estimating animal density from point transect surveys in which the conventional point transect assumption of uniform animal distribution in the vicinity of the point is violated.It includes tools for plotting, model selection, goodness-of-fit testing and simulation.This paper describes the main features of the package and illustrates its use by application to two different kinds of survey dataset.
The purpose of this review was to assess the historic and current efforts to estimate trends and ... more The purpose of this review was to assess the historic and current efforts to estimate trends and abundance of humpback whales on the east and west coast of Australia (breeding stocks D and E), and to develop recommendations of how to proceed with this work into the future
There is growing interest from research and conservation groups in the potential for using small ... more 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 ti...
A camera system was previously developed to augment an aerial survey programme which targeted Ant... more A camera system was previously developed to augment an aerial survey programme which targeted Antarcti c minke whales in East Antarctica. The purpose of this camera system was to record the presence of wh ales beneath the aircraft and to provide informatio n regarding local sea ice conditions. Although this aerial survey programme has finished, we arranged for flig hts to take photographs of potential whale habitat within Vincennes Bay (East Antarctica 66o 24’S 110o 8’E) when aircraft time allowed during the normal summer aviation schedule of the Australian Antarctic Divi s on. Digital photographs of potential whale habita t were derived from two flights on 2 and 23 January, 2011, covering around 47 and 42 km 2 of sea surface, respectively. Unfortunately photog raphs from both flights did not yield any whale sightings. This result is compa red and contrasted to whale sightings in photograph s taken during a single day of an aerial survey dur ing the 2008/09 summer season. It is hope...
There is global recognition that ship strike represents a significant risk to some populations of... more There is global recognition that ship strike represents a significant risk to some populations of whales around the world. Analysis of ship strike records worldwide demonstrates that humpback whales are the second most frequently reported whale species to be struck by a ship. In Australia, both the east and west coast populations of humpback whales are strongly recovering from commercial whaling during the mid-20th century which resulted in populations nearing extinction. On the east coast of Australia the main breeding ground for humpback whales is within the Great Barrier Reef World Heritage Area (GBRWHA). Both the east and west coast of Australia have also in the past decade experienced considerable coastal and port development associated with an increase in natural resource projects. It is due to substantial coastal development and port expansions related to the mining industry that UNESCO were considering listing the GBRWHA on the ‘List of World Heritage in Danger’ and are curr...
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Under the snow: a new camera trap opens the white box of subnivean ecology Research 2068 41 2016 ... more Under the snow: a new camera trap opens the white box of subnivean ecology Research 2068 41 2016 From imagery to ecology: leveraging time series of all available Landsat observations to map and monitor ecosystem state and dynamics Research 1763 23 2016 Patterns of twenty-first century forest loss across a global network of important sites for biodiversity Research 1712 104 2015 Testing the water: detecting artificial water points using freely available satellite data and open source software Research 1586 30 2016 Is waveform worth it? A comparison of LiDAR approaches for vegetation and landscape characterization Interdisciplinary perspectives 1563 19 2015 Life-history attributes and resource dynamics determine intraspecific home-range sizes in Carnivora Research 1532 33 2015 High-resolution forest canopy height estimation in an African blue carbon ecosystem Research 1502 46 2016 Wildlife speed cameras: measuring animal travel speed and day range using camera traps Research 1287 27 2016 An invasive-native mammalian species replacement process captured by camera trap survey random encounter models Research 1135 28 2016 Sea turtle nesting patterns in Florida visa -vis satellite-derived measures of artificial lighting Research 1057 84 2016 Remote sensing of species dominance and the value for quantifying ecosystem services Interdisciplinary perspectives 1017 12 2016 Integrating LiDAR-derived tree height and Landsat satellite reflectance to estimate forest regrowth in a tropical agricultural landscape Research 988 48 2016 How do passive infrared triggered camera traps operate and why does it matter? Breaking down common misconceptions Interdisciplinary perspectives 966 14 2016 The higher you go the less you will know: placing camera traps high to avoid theft will affect detection Research 858 33 2016 The role of space agencies in remotely sensed essential biodiversity variables Policy forum 843 18 2016 Observing ecosystems with lightweight, rapid-scanning terrestrial lidar scanners Research 747 11 2016 A simple remote sensing based information system for monitoring sites of conservation importance Interdisciplinary perspectives 616 1 2016 Upland vegetation mapping using Random Forests with optical and radar satellite data Research 449 13 2016 Ultrasonic monitoring to assess the impacts of forest conversion on Solomon Island bats Research 420 19 2016 Earth observation archives for plant conservation: 50 years monitoring of Itigi-Sumbu thicket Research 377 12 54
Estimating abundance of Antarctic minke whales is central to the International Whaling Commission... more Estimating abundance of Antarctic minke whales is central to the International Whaling Commission's conservation and management work and understanding impacts of climate change on polar marine ecosystems. Detecting abundance trends is problematic, in part because minke whales are frequently sighted within Antarctic sea ice where navigational safety concerns prevent ships from surveying. Using icebreaker-supported helicopters, we conducted aerial surveys across a gradient of ice conditions to estimate minke whale density in the Weddell Sea. The surveys revealed substantial numbers of whales inside the sea ice. The Antarctic summer sea ice is undergoing rapid regional change in annual extent, distribution, and length of ice-covered season. These trends, along with substantial interannual variability in ice conditions, affect the proportion of whales available to be counted by traditional shipboard surveys. The strong association between whales and the dynamic, changing sea ice req...
One hypothesis put forward to explain the putative drop in abundance of Antarctic minke whales, a... more One hypothesis put forward to explain the putative drop in abundance of Antarctic minke whales, as derived from the IDCR/SOWER programme, between CPII (1984/85-1990/91) and CPIII (1991/92-2003/04) was that the animals were distributed more within sea ice regions during the CPIII period (i.e., away from survey transects). There is no way to test this hypothesis in a strict sense, but with new estimates of density of Antarctic minke whales (from aerial surveys) in particular areas of sea ice (Weddell Sea and east Antarctica), and model-based abundance methods which allow extrapolation, there is an opportunity to compare bounds and magnitudes of abundances to at least judge how likely the ‘moved-into-sea ice’ hypothesis is. In the first instance, it is recommended that comparisons of inside/outside abundances be made for areas and years where the aerial surveys were conducted. If these analyses are inconclusive, there is a recommendation to extend the analysis to estimating circumpolar densities, and extrapolating back over the period of CPII and CPIII, with full consideration given to how variable minke whale densities can be over space and time. However, until estimates of availability bias are produced, absolute abundance estimates for areas and seasons over which the aerial surveys were conducted will not be possible. Finally, in the event that large numbers of minke whales are in fact to be found in sea ice regions, there may be a case to undertake more aerial surveys in order to produce truly unbiased estimates of circumpolar minke whale abundances from any post-CPIII era survey efforts.
The Australian Government supported aerial surveys over sea ice covered regions of East Antarctic... more The Australian Government supported aerial surveys over sea ice covered regions of East Antarctica with the aim to begin to estimate the proportion of Antarctic minke whales not accessible to sighting surveys in open water. The aerial surveys were undertaken in the austral summers of 2008/09 and 2009/10. Our aerial survey programme is the first systematic survey of distribution and abundance of Antarctic minke whales in sea ice, both within and between summer seasons. During these surveys, around 15 000 km of effort was achieved across 20º of longitude (93-110º E), yielding 65 sightings of minke whales (94 individuals). We produced model-based estimates of uncorrected abundances and densities (uncorrected for availability bias) within sea ice between 93-110ºE, and we present discussion on the range of corrected estimates possible given our current lack of data on availability bias for Antarctic minke whales in sea ice regions. Using 'pro rated' abundances from IDCR/SOWER, leveraged on simple estimates of encounter rate, there is some evidence that between 10 and 50% the minke population may have been within ice over those longitudes 93-113ºE during the 2009/10 summer. So we can conclude that the proportion of minke whales in ice regions is probably considerable, and will be an influence on biases on abundance estimates for open water regions. There is a clear need for more research to estimate availability bias in Antarctic minke whales.
Many populations of southern hemisphere baleen whales are recovering and are again becoming domin... more Many populations of southern hemisphere baleen whales are recovering and are again becoming dominant consumers in the Southern Ocean. Key to understanding the present and future role of baleen whales in Southern Ocean ecosystems is determining their abundance on foraging grounds. Distance sampling is the standard method for estimating baleen whale abundance but requires specific logistic requirements which are rarely achieved in the remote Southern Ocean. We explore the potential use of tourist vessel-based sampling as a cost-effective solution for conducting distance sampling surveys for baleen whales in the Southern Ocean. We used a dataset of tourist vessel locations from the southwest Atlantic sector of the Southern Ocean and published knowledge from Southern Ocean sighting surveys to determine the number of tourist vessel voyages required for robust abundance estimates. Second, we simulated the abundance and distributions of four baleen whale species for the study area and samp...
Aerial surveys are frequently used to estimate the abundance of marine mammals, but their accurac... more Aerial surveys are frequently used to estimate the abundance of marine mammals, but their accuracy is dependent upon obtaining a measure of the availability of animals to visual detection. Existing methods for characterizing availability have limitations and do not necessarily reflect true availability. Here, we present a method of using small, vessel-launched, multi-rotor Unoccupied Aerial Vehicles (UAVs, or drones) to collect video of dolphins to characterize availability and investigate error surrounding group size estimates. We collected over 20 h of aerial video of dive-surfacing behaviour across 32 encounters with Australian humpback dolphins Sousa sahulensis off northwestern Australia. Mean surfacing and dive periods were 7.85 sec (se = 0.26) and 39.27 sec (se = 1.31) respectively. Dolphin encounters were split into 56 focal follows of consistent group composition to which example approaches to estimating availability were applied. Non-instantaneous availability estimates, assuming a 7 sec observation window, ranged between 0.22 and 0.88, with a mean availability of 0.46 (CV = 0.34). Availability tended to increase with increasing group size. We found a downward bias in group size estimation, with true group size typically one individual more than would have been estimated by a human observer during a standard aerial survey. The variability of availability estimates between focal follows highlights the importance of sampling across a variety of group sizes, compositions and environmental conditions. Through data re-sampling exercises, we explored the influence of sample size on availability estimates and their precision, with results providing an indication of target sample sizes to minimize bias in future research. We show that UAVs can provide an effective and relatively inexpensive method of characterizing dolphin availability with several advantages over existing approaches. The example estimates obtained for humpback dolphins are within the range of values obtained for other shallow-water, small cetaceans, and will directly inform a government-run program of aerial surveys in the region.
An automated algorithm for passive acoustic detection of blue whale D-calls is developed based on... more An automated algorithm for passive acoustic detection of blue whale D-calls is developed based on established deep learning methods for image recognition via the DenseNet architecture. Koogu—an open-source Python package—was used for developing the detector. The detector was trained on annotated acoustic recordings from the Antarctic, and the performance of the detector was assessed by calculating precision and recall using a separate independent dataset also from the Antarctic. Detections from both the human analyst and automated detector were then inspected by a more experienced analyst to identify any calls missed by either approach and to adjudicate whether the apparent false-positive detections from the automated approach were actually true-positives. Lastly, an additional performance assessment was conducted using double-platform methods (via a closed-population Huggins mark recapture model) to assess the probability of detection of both the human analyst and automated detecto...
The Australian Antarctic Division of the Australian Government is planning an Antarctic Blue Whal... more The Australian Antarctic Division of the Australian Government is planning an Antarctic Blue Whale Voyage in the austral summer of 2013. This voyage is a project of the Southern Ocean Research Partnership’s (SORP ) Antarctic Blue Whale P roject. The Antarctic Blue Whale Project aims to develop technologies and collect data that will result in an estimation of the abundance of Antarctic Blue Whales (Balaenoptera musculus intermedia), improve understanding of population structure and linkages between breeding a nd feeding grounds, and characterise the behaviour in the feeding grounds. The 2013 Antarctic Blue Whale Voyage aims to further develop passive acoustic tracking methodologies to increase sighting rates of Antarctic Blue Whales. Individuals identified based on photography identification, genetic biopsies and tagging will contribute to further develop mark-and-recapture methods to meet the aims of the Antarctic Blue Whale Project. The voyage is currently planned to be a minimum ...
ABSTRACT The R package nupoint provides tools for estimating animal density from point transect s... more ABSTRACT The R package nupoint provides tools for estimating animal density from point transect surveys in which the conventional point transect assumption of uniform animal distribution in the vicinity of the point is violated.It includes tools for plotting, model selection, goodness-of-fit testing and simulation.This paper describes the main features of the package and illustrates its use by application to two different kinds of survey dataset.
The purpose of this review was to assess the historic and current efforts to estimate trends and ... more The purpose of this review was to assess the historic and current efforts to estimate trends and abundance of humpback whales on the east and west coast of Australia (breeding stocks D and E), and to develop recommendations of how to proceed with this work into the future
There is growing interest from research and conservation groups in the potential for using small ... more 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 ti...
A camera system was previously developed to augment an aerial survey programme which targeted Ant... more A camera system was previously developed to augment an aerial survey programme which targeted Antarcti c minke whales in East Antarctica. The purpose of this camera system was to record the presence of wh ales beneath the aircraft and to provide informatio n regarding local sea ice conditions. Although this aerial survey programme has finished, we arranged for flig hts to take photographs of potential whale habitat within Vincennes Bay (East Antarctica 66o 24’S 110o 8’E) when aircraft time allowed during the normal summer aviation schedule of the Australian Antarctic Divi s on. Digital photographs of potential whale habita t were derived from two flights on 2 and 23 January, 2011, covering around 47 and 42 km 2 of sea surface, respectively. Unfortunately photog raphs from both flights did not yield any whale sightings. This result is compa red and contrasted to whale sightings in photograph s taken during a single day of an aerial survey dur ing the 2008/09 summer season. It is hope...
There is global recognition that ship strike represents a significant risk to some populations of... more There is global recognition that ship strike represents a significant risk to some populations of whales around the world. Analysis of ship strike records worldwide demonstrates that humpback whales are the second most frequently reported whale species to be struck by a ship. In Australia, both the east and west coast populations of humpback whales are strongly recovering from commercial whaling during the mid-20th century which resulted in populations nearing extinction. On the east coast of Australia the main breeding ground for humpback whales is within the Great Barrier Reef World Heritage Area (GBRWHA). Both the east and west coast of Australia have also in the past decade experienced considerable coastal and port development associated with an increase in natural resource projects. It is due to substantial coastal development and port expansions related to the mining industry that UNESCO were considering listing the GBRWHA on the ‘List of World Heritage in Danger’ and are curr...
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Under the snow: a new camera trap opens the white box of subnivean ecology Research 2068 41 2016 ... more Under the snow: a new camera trap opens the white box of subnivean ecology Research 2068 41 2016 From imagery to ecology: leveraging time series of all available Landsat observations to map and monitor ecosystem state and dynamics Research 1763 23 2016 Patterns of twenty-first century forest loss across a global network of important sites for biodiversity Research 1712 104 2015 Testing the water: detecting artificial water points using freely available satellite data and open source software Research 1586 30 2016 Is waveform worth it? A comparison of LiDAR approaches for vegetation and landscape characterization Interdisciplinary perspectives 1563 19 2015 Life-history attributes and resource dynamics determine intraspecific home-range sizes in Carnivora Research 1532 33 2015 High-resolution forest canopy height estimation in an African blue carbon ecosystem Research 1502 46 2016 Wildlife speed cameras: measuring animal travel speed and day range using camera traps Research 1287 27 2016 An invasive-native mammalian species replacement process captured by camera trap survey random encounter models Research 1135 28 2016 Sea turtle nesting patterns in Florida visa -vis satellite-derived measures of artificial lighting Research 1057 84 2016 Remote sensing of species dominance and the value for quantifying ecosystem services Interdisciplinary perspectives 1017 12 2016 Integrating LiDAR-derived tree height and Landsat satellite reflectance to estimate forest regrowth in a tropical agricultural landscape Research 988 48 2016 How do passive infrared triggered camera traps operate and why does it matter? Breaking down common misconceptions Interdisciplinary perspectives 966 14 2016 The higher you go the less you will know: placing camera traps high to avoid theft will affect detection Research 858 33 2016 The role of space agencies in remotely sensed essential biodiversity variables Policy forum 843 18 2016 Observing ecosystems with lightweight, rapid-scanning terrestrial lidar scanners Research 747 11 2016 A simple remote sensing based information system for monitoring sites of conservation importance Interdisciplinary perspectives 616 1 2016 Upland vegetation mapping using Random Forests with optical and radar satellite data Research 449 13 2016 Ultrasonic monitoring to assess the impacts of forest conversion on Solomon Island bats Research 420 19 2016 Earth observation archives for plant conservation: 50 years monitoring of Itigi-Sumbu thicket Research 377 12 54
Estimating abundance of Antarctic minke whales is central to the International Whaling Commission... more Estimating abundance of Antarctic minke whales is central to the International Whaling Commission's conservation and management work and understanding impacts of climate change on polar marine ecosystems. Detecting abundance trends is problematic, in part because minke whales are frequently sighted within Antarctic sea ice where navigational safety concerns prevent ships from surveying. Using icebreaker-supported helicopters, we conducted aerial surveys across a gradient of ice conditions to estimate minke whale density in the Weddell Sea. The surveys revealed substantial numbers of whales inside the sea ice. The Antarctic summer sea ice is undergoing rapid regional change in annual extent, distribution, and length of ice-covered season. These trends, along with substantial interannual variability in ice conditions, affect the proportion of whales available to be counted by traditional shipboard surveys. The strong association between whales and the dynamic, changing sea ice req...
One hypothesis put forward to explain the putative drop in abundance of Antarctic minke whales, a... more One hypothesis put forward to explain the putative drop in abundance of Antarctic minke whales, as derived from the IDCR/SOWER programme, between CPII (1984/85-1990/91) and CPIII (1991/92-2003/04) was that the animals were distributed more within sea ice regions during the CPIII period (i.e., away from survey transects). There is no way to test this hypothesis in a strict sense, but with new estimates of density of Antarctic minke whales (from aerial surveys) in particular areas of sea ice (Weddell Sea and east Antarctica), and model-based abundance methods which allow extrapolation, there is an opportunity to compare bounds and magnitudes of abundances to at least judge how likely the ‘moved-into-sea ice’ hypothesis is. In the first instance, it is recommended that comparisons of inside/outside abundances be made for areas and years where the aerial surveys were conducted. If these analyses are inconclusive, there is a recommendation to extend the analysis to estimating circumpolar densities, and extrapolating back over the period of CPII and CPIII, with full consideration given to how variable minke whale densities can be over space and time. However, until estimates of availability bias are produced, absolute abundance estimates for areas and seasons over which the aerial surveys were conducted will not be possible. Finally, in the event that large numbers of minke whales are in fact to be found in sea ice regions, there may be a case to undertake more aerial surveys in order to produce truly unbiased estimates of circumpolar minke whale abundances from any post-CPIII era survey efforts.
The Australian Government supported aerial surveys over sea ice covered regions of East Antarctic... more The Australian Government supported aerial surveys over sea ice covered regions of East Antarctica with the aim to begin to estimate the proportion of Antarctic minke whales not accessible to sighting surveys in open water. The aerial surveys were undertaken in the austral summers of 2008/09 and 2009/10. Our aerial survey programme is the first systematic survey of distribution and abundance of Antarctic minke whales in sea ice, both within and between summer seasons. During these surveys, around 15 000 km of effort was achieved across 20º of longitude (93-110º E), yielding 65 sightings of minke whales (94 individuals). We produced model-based estimates of uncorrected abundances and densities (uncorrected for availability bias) within sea ice between 93-110ºE, and we present discussion on the range of corrected estimates possible given our current lack of data on availability bias for Antarctic minke whales in sea ice regions. Using 'pro rated' abundances from IDCR/SOWER, leveraged on simple estimates of encounter rate, there is some evidence that between 10 and 50% the minke population may have been within ice over those longitudes 93-113ºE during the 2009/10 summer. So we can conclude that the proportion of minke whales in ice regions is probably considerable, and will be an influence on biases on abundance estimates for open water regions. There is a clear need for more research to estimate availability bias in Antarctic minke whales.
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