Hodgson A.,Murdoch University |
Kelly N.,CSIRO |
Kelly N.,Australian Marine Mammal Center |
Peel D.,CSIRO |
Peel D.,Australian Marine Mammal Center
PLoS ONE | Year: 2013
Aerial surveys of marine mammals are routinely conducted to assess and monitor species' habitat use and population status. In Australia, dugongs (Dugong dugon) are regularly surveyed and long-term datasets have formed the basis for defining habitat of high conservation value and risk assessments of human impacts. Unmanned aerial vehicles (UAVs) may facilitate more accurate, human-risk free, and cheaper aerial surveys. We undertook the first Australian UAV survey trial in Shark Bay, western Australia. We conducted seven flights of the ScanEagle UAV, mounted with a digital SLR camera payload. During each flight, ten transects covering a 1.3 km2 area frequently used by dugongs, were flown at 500, 750 and 1000 ft. Image (photograph) capture was controlled via the Ground Control Station and the capture rate was scheduled to achieve a prescribed 10% overlap between images along transect lines. Images were manually reviewed post hoc for animals and scored according to sun glitter, Beaufort Sea state and turbidity. We captured 6243 images, 627 containing dugongs. We also identified whales, dolphins, turtles and a range of other fauna. Of all possible dugong sightings, 95% (CI = 90%, 98%) were subjectively classed as 'certain' (unmistakably dugongs). Neither our dugong sighting rate, nor our ability to identify dugongs with certainty, were affected by UAV altitude. Turbidity was the only environmental variable significantly affecting the dugong sighting rate. Our results suggest that UAV systems may not be limited by sea state conditions in the same manner as sightings from manned surveys. The overlap between images proved valuable for detecting animals that were masked by sun glitter in the corners of images, and identifying animals initially captured at awkward body angles. This initial trial of a basic camera system has successfully demonstrated that the ScanEagle UAV has great potential as a tool for marine mammal aerial surveys. Copyright: © 2013 Hodgson et al.
Gedamke J.,Australian Marine Mammal Center |
Robinson S.M.,Australian Marine Mammal Center
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2010
A large scale, systematic, acoustic survey for whales and seals in eastern Antarctic waters was conducted in January-February 2006. During the BROKE-West survey of Southern Ocean waters between 30 and 80° E longitude, an acoustic survey was conducted to complement a traditional visual survey for marine mammal occurrence and distribution. As part of the survey, 145 DIFAR sonobuoys were deployed every 30' of latitude on north-south transects, and prior to CTD stations on the initial east-west transect. Underwater sound was analyzed for 70 minute samples from each sonobuoy. Blue whales were the most commonly recorded species, identified at 55 of the sonobuoy deployment sites. Other species recorded include: sperm (46 sites), fin (14), humpback (2), and sei (3) whales, and leopard (11) and Ross (17) seals. Large numbers of blue and sperm whales, and all Ross seals were detected on the westernmost two transects, which were the only transects of the survey with relatively extensive sea ice remaining off the continental shelf. Large numbers of blue whales were also detected in the more eastern waters of the survey off the Prydz Bay region, while two detections of pygmy blue whales represent the farthest south these whales have been recorded. Of the relatively few fin whale detections, most occurred in more northerly waters. Fin whale vocalizations from this region were distinctly different than those recorded elsewhere around Antarctica suggesting acoustic recordings may be useful to delineate regional or stock boundaries of this species. Previously undescribed sounds were attributed to Ross seals. Acoustic detections of these and leopard seal sounds indicate these animals venture further from their traditionally described distributions, with vocalizing leopard seals occurring much further north than might be expected. Overall, the results of the sonobuoy survey provide a measure of each species' relative spatial distribution over the survey area based on acoustic detections, and when combined with the results of the visual survey, will provide a comprehensive view of marine mammal distribution throughout the region during the BROKE-West survey. Crown Copyright © 2009.