Florida manatees (Trichechus manatus latirostris) are known to range north into the U.S. midAtlantic during warmer summer and fall months. However, rapid cooling of water temperatures in the fall can be detrimental to their survival in this region. This study reports upon all known manatee sightings (n = 211) and strandings (n = 9) from 1991 to 2012 in North Carolina and Virginia. The goals were to describe spatial and temporal patterns of manatee habitat use and mortality and relate those patterns to seasonal water temperatures, and to develop a finer-scale understanding of environmental temperatures across the region by deploying temperature data loggers at multiple sites throughout inland and coastal waterways.Although sightings were opportunistically gathered and, thus, not corrected for effort, they reveal a consistent picture of manatee presence in the midAtlantic. In both states, sightings were most common from June to October when water temperatures were above 20° C. Sightings in North Carolina were most common in the Intracoastal Waterway (27%), and in rivers and creeks (46%) in Virginia. Fine-scale temperature data collected throughout the region demonstrated highly variable, declining water temperatures in late fall, with temperatures dropping by as much as 1.35° C/d. Manatee sightings decreased precipitously with water temperature in November, while strandings increased. The results of this study demonstrate that manatees are predictably found in North Carolina and Virginia throughout the late spring, summer, and fall. These data can be used to plan future education and outreach, monitoring, regulatory actions, and habitat protection measures for this endangered species in this region.
Beaked whales are vulnerable to the impacts of disturbance from several sources of anthropogenic sound. Here we report the distribution and abundance of beaked whales off Cape Hatteras, North Carolina, U.S.A., an area utilized by the U.S. Navy for training exercises, and of particular interest for seismic geophysical surveys. From May 2011 through November 2015, monthly aerial surveys were conducted at the site. Beaked whales were encountered 74 times (n 5 205 individuals) during these surveys. Ziphius cavirostris, the most commonly encountered species, was observed in every month of the year. Mesoplodon spp. were encountered in ten months of the year. Photographs of adult males with erupted teeth permitted six sightings to be identified conclusively as M. europaeus; M. mirus was also photographed just outside the study area. Beaked whale surface densities stratified by depth (0.005-0.007/km 2 ) were among the highest reported in the world for small ziphiids. A quantitative comparison of sightings and stranding records suggests that strandings do not accurately reflect the relative abundance of beaked whale species in this area. We conclude that Cape Hatteras, at the convergence of the Labrador Current and Gulf Stream, is a particularly important year-round habitat for several species of beaked whales.
In this paper the occurrence, distribution and abundance of cetaceans in offshore waters of Onslow Bay, North Carolina, USA is described. Between June 2007 and June 2010 monthly aerial and shipboard line-transect surveys were conducted along ten 74km transects placed perpendicular to the shelf break. In total 42,676km of aerial trackline (218 sightings) and 5,209km of vessel trackline (100 sightings) were observed. Seven species of cetaceans were observed, but the fauna was dominated strongly by common bottlenose and Atlantic spotted dolphins. Both species were present year-round in the study area. Using photo-identification techniques, five bottlenose dolphins and one spotted dolphin were resighted during the three-year period. In general, the abundance of cetaceans in Onslow Bay was low and too few sightings were made to estimate monthly abundances for species other than bottlenose and spotted dolphins. Maximum monthly abundances of bottlenose and spotted dolphins were 4,100 (95% CI: 1,300–9,400) in May 2010 and 6,000 (95% CI: 2,500–17,400) in March 2009, respectively. Bottlenose dolphins were found throughout the study area, although they were encountered most frequently just off the shelf break. In contrast, spotted dolphins exhibited a strong preference for waters over the continental shelf and were not encountered beyond the shelf break.
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