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Search Completed | Title | Using a small, consumer-grade drone to identify and count marine megafauna
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Lat. Am. J. Aquat. Res., 46(5): 1025-1033, 2018
Quantifying marine megafauna abundances with a small drone
Using a small, consumer-grade drone to identify and count marine megafauna in shallow habitats
Enie Hensel1, Stephanie Wenclawski2 & Craig A. Layman1
1Department of Applied Ecology, North Carolina State University, Raleigh, North Carolina, USA 2Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University
Raleigh North Carolina, USA Corresponding author: Enie Hensel (firstname.lastname@example.org)
ABSTRACT. Large-bodied animals, megafauna, are disproportionately threatened and yet, remain relatively difficult to monitor, particularly true in the ocean. Consumer-grade drones have high definition imagery and offer a non-invasive way to monitor a subset of marine megafauna, especially those species that spend part of their life near the water’s surface. However, a key question is the extent to which drone imagery data offer reliable abundance estimates due to potential detection restraints, and the ability to compare data from different locations. Here we tested the efficacy of a quadcopter drone to collect megafauna abundance data in multiple shallow-water habitats in the realistic background variation of shoreline development. On Great Abaco Island, The Bahamas we repeated drone surveys in nearshore habitats from June to August 2015 at three paired high and low human population sites. We tested the drone's detection probability using decoy organisms and found no effect of water quality or benthic characteristics on detectability. In short, the drones appear to work to monitor these species. We also noted patterns in the occupancy of the species on which we focused. We observed three shark, two ray, and two sea turtle species, finding higher abundances of all species in our low human population sites compared to high human population sites. Our results highlight the ability of consumer-grade drones to estimate the abundance and distribution of large-bodied elasmobranchs and sea turtles in shallow water habitats. Further, our study supports their capability to evaluate issues related to the conservation and management of nearshore ecosystems.
Keywords: Unmanned Aerial Vehicles (UAVs), non-invasive monitoring, human impacts.
Large-bodied animals, megafauna, are some of the animals most vulnerable to and impacted by human activities (Lewison et al., 2004; Dirzo et al., 2014). Many megafauna species, particularly marine species, remain difficult to monitor due to their large home ranges and sensitivity to being captured and handled (Hueter & Manire, 1994). Aerial surveys are one methodology used to measure the size, density, and distribution of megafauna populations that spend part of their life near the ocean’s surface (Loughlin et al., 1992; Pollock et al., 2006; Koski et al., 2009). Aerial surveys allow researchers to monitor animals with low to no intrusion, thereby minimizing biases in observer presence and a detriment to animals (Jolly 1969; Hodgson et al., 2013; Christie et al., 2016). Traditio- nally conducted with observers on a small aircraft or a type of Unmanned Aerial Systems (UASs), such as
Corresponding editor: Amilcar Cupul
military Unmanned Aerial Vehicles (UAVs), aerial surveys were limited to studies that could obtain proper aircraft permits and meet budgetary requirements (Pollock et al., 2006). In the last decade, small, consumer-grade UAVs, herein drones, have become readily available, increasing the use of aerial imagery to study a wide range of fauna and flora, likely due to these drones being more affordable and easier to use than more traditional UASs (Koh & Wich, 2012). Also, technological advancements in camera imagery have increased detection probability from traditional aerial monitoring methods (Grier et al., 1981; Hodgson et al., 2013). Because of these improvements, small, consumer-grade drones may be a promising tool to assist conservation and management agencies in assessing how human activities affect sensitive marine megafauna.
Aerial surveys conducted in marine environments, either by manned aircraft or drones, have focused mainly
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