The use of drones to study marine animals shows promise for the examination of numerous aspects of their ecology, behaviour, health and movement patterns. However, the responses of some marine phyla to the presence of drones varies broadly, as do the general operational protocols used to study them. Inconsistent methodological approaches could lead to difficulties comparing studies and can call into question the repeatability of research. This review draws on current literature and researchers with a wealth of practical experience to outline the idiosyncrasies of studying various marine taxa with drones. We also outline current best practice for drone operation in marine environments based on the literature and our practical experience in the field. The protocols outlined herein will be of use to researchers interested in incorporating drones as a tool into their research on marine animals and will help form consistent approaches for drone-based studies in the future.

The Vulnerable Antillean manatee Trichechus manatus manatus (Mammalia, Sirenia) is threatened by hunting, entanglement in fishing nets and habitat degradation but most knowledge of the species comes from coastal and estuarine populations. We therefore studied an Antillean manatee population located .1,100 km from the Caribbean coast, in the Orinoco River of Colombia, during 2001-2005. To verify the occurrence of the manatee and to investigate its habitat use throughout the annual hydrological cycle, we carried out surveys for manatees and manatee feeding signs over c. 40 km of the Orinoco River, between El Burro and Bachaco. We made 870 sightings in 1,003 hours of observation, and found 69 feeding areas in 776 hours of surveys. From 82 interviews in a total of 28 locations in Venezuela and Colombia we compiled 90 reports of manatees injured or killed in the Orinoco during 1980-2004. Both habitat use by the manatee and anthropogenic impacts on the species vary with the annual hydrological cycle. Reproduction appears to occur during the low water period in restricted areas that retain deep water. Improved knowledge of the dynamics of manatee migration and regulation of human activities, especially those related to use of nets and boat traffic, are required for conservation of the Antillean manatee in this freshwater habitat.

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Dolphins of the genus Stenella occur in pelagic waters of both tropical and warmtemperate oceans. Three species, the Atlantic spotted dolphin (Stenella frontalis), the pantropical spotted dolphin (S. attenuata), and the spinner dolphin (S. longirostris) are abundant worldwide, but in the Caribbean Basin they have been poorly studied and information on their distribution patterns is scarce. Specifically, in Colombia's remote Seaflower Biosphere Reserve (SFBR) S. attenuata has been reported occasionally, but S. frontalis and S. longirostris have never been recorded before. To address this information gap, an ecological niche modeling approach was used to determine the potential distribution patterns of these three dolphin species in the region. Records of these species for the Caribbean Basin were compiled, including both published and unpublished data. Environmental information, including bathymetry, bathymetric slope, distance to shore, sea surface temperature, sea surface salinity, and chlorophylla concentration was gathered from public databases (MARSPEC and Bio-ORACLE) in raster format. The maximum entropy algorithm (Maxent) for modeling species' geographic distributions with presence-only data was used. After filtering the data, 210 records of S. attenuata, 204 of S. frontalis, and 80 of S. longirostris were used to run models. The best configuration for each model was chosen based on the AICc criterion. For all three species, the final ecological niche models returned AUC

Information from 15 satellite‐tracked Antillean manatees (Trichechus manatus manatus) was analyzed in order to assess individual movements, home ranges, and high‐use areas for conservation decisions. Manatees were captured in Chetumal Bay, Mexico, and tagged with Argos‐monitored satellite transmitters. Location of the manatees and physical characteristics were assessed to describe habitat properties. Most manatees traveled to freshwater sources. The Maximum Area Size (MAS) for each manatee was determined using the observation‐area method. Additional kernel densities of 95% home range and 50% Center of Activity (COA) were also calculated, with manatees having 1–3 COAs. Manatees exhibited two different movement patterns: remaining in Chetumal Bay, and long‐distance (up to 240 km in 89 d). The residence time in Chetumal Bay was higher for females (89.6% of time) than for males (72.0%), but the daily travel rate (0.4–0.5 km/d) was similar for both sexes. Most of the COAs fell within Natural Protected Areas (NPA). However, manatees also travel for long distances into unprotected areas, where they face uncontrolled boat traffic, fishing activities, and habitat loss. Conservation of movement corridors may promote long‐distance movements and facilitate genetic exchange.

During 2005-2007, a series of interviews were carried out with the riverside populations of the Oil Province of Urucu (AM, Brasil). The main goal of this work was to characterize the knowledge of the inhabitants of this area regarding the Amazonian manatee (Trichechus inunguis) (listed as Vulnerable on the IUCN Red List). Interviews were conducted with 74 local inhabitants from 33 communities. Between 2004 and 2007, 20 poached or entangled Amazonian manatees were reported in the area. Poaching with harpoon is the principal cause of mortality, but manatees are also incidentally caught in fishing nets. Interviewers described details of manatee hunting techniques in the area. The trade of manatee meat, although currently forbidden by Brazilian laws, still occurs in the area. Data obtained from the interviews suggest a dietary preference of the manatee for at least 29 species of aquatic and semi-aquatic plants. The interviewed fishermen showed a sound knowledge of Amazonian manatee biology and behavior. This information may be important to assist future conservation plans in the Amazon.

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Population assessments and species monitoring for many endangered marine megafauna are limited by the challenges of identifying and tracking individuals that live underwater in remote and sometimes inaccessible areas. Manatees can acquire scars from watercraft injury and other incidences that can be used to identify individuals. Here we describe a novel method for photo-identification of Antillean manatees Trichechus manatus manatus using aerial imagery captured during flights with a small multirotor drone. Between 2016 and 2017, we conducted 103 flights to detect and observe manatees in Belize, primarily at St. George's Caye (SGC) near the Belize Barrier Reef. Review of aerial videos from these flights resulted in 279 sightings of manatees (245 adults, 34 calves). High-resolution images of individual manatees were extracted and classified according to image quality and distinctiveness of individual manatees for photoidentification. High-quality images of manatees classified as sufficiently distinctive were used to create a catalog of 17 identifiable individuals. At SGC, 21% of all sighted adult manatees (N = 214) were considered photo-identifiable over time. We suggest that the method can be used for investigating individual site fidelity, habitat use, and behavior of manatee populations. Our photoidentification protocol has the potential to improve long-term monitoring of Antillean manatees in Belize and can be applied throughout clear, shallow waters in the Caribbean and elsewhere.