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- Cetacean and sea turtle observations in the remote mid-atlantic (NW) oceanPublication . Wachtendonk, Rachel; Smultea, Mari A.; Pedrie, KolbyDue to its remoteness, little is known about the occurrence and abundance of cetaceans and sea turtles in the pelagic mid-Atlantic Ocean. Data on cetacean and sea turtle occurrence and distribution were collected by dedicated biological observers to address U.S. monitoring and mitigation requirements associated with a vessel based academic geophysical survey in international waters in the northwestern and mid -Atlantic Ocean from 14 June through 16 July 2018. A total of 6,949 km (503 h) of visual observations occurred while surveying north from Bermuda and ending in Woods Hole, Massachusetts. A total of 928 cetaceans representing at least 14 species and 15 sea turtles representing three species were observed. The most frequently observed cetacean species was the Atlantic white-sided dolphin (Lagenorhynchus acutus) (340 individuals; 37%) followed by the short-beaked common dolphin (Delphinus delphis) (286 individuals; 31%) and pilot whales (Globicephala spp.) (95 individuals; 10%). These sighting data also included an extralimital sighting of a sperm whale (Physeter macrocephalus) calf at 43.44 degrees N latitude and 36.85 degrees W longitude, and extralimital sightings of Atlantic white-sided dolphins below 38 degrees N latitude. Loggerhead sea turtles (Caretta caretta) were seen most frequently (6 individuals). This study addresses a data gap in documented occurrence and lack of occurrence of cetaceans and sea turtles over a large pelagic area in the northwestern Atlantic Ocean during summer.
- Blue whale body condition assessed over a 14-year period in the NE Pacific: annual variation and connection to measures of ocean productivityPublication . Wachtendonk, Rachel; Calambokidis, John; Flynn, KiirstenLarge marine mammals can serve as an indicator of the overall state of the environment due to their apex position in marine food webs and their functions as sentinels of change. Reductions in prey, driven by changes in environmental conditions can manifest in reduced fat stores that are visible on whales. We developed a non-invasive technique using photographs of blue whales taken on the US west coast from 2005-2018 (n=3,660) and scored body condition based on visible undulations from the vertebral processes and body shape. We analyzed patterns in the body condition of whales across years and their relation to oceanographic conditions. Females with calves had significantly poorer body conditions and calves had significantly better body conditions compared to other adult whales (Chi-Square, x(2 =) 170.36, df=6, p<2.2e-16). Year was a significant factor in body condition (Chi-Square, x(2 =) 417.73, df=39, p<0.001). The highest proportion of whales in poor body condition was observed for 2015 (one of the only two years along with 2017 where >50% had poor body condition) coincides with the marine heat wave that affected the NE Pacific 2014-2016. A cumulative mixed model examining the relationship between body condition and environmental variables revealed that negative Pacific Decadal Oscillation and longer upwelling seasons correlated with better blue whale body condition, likely to be due to higher primary productivity and prey availability. This study indicates that with an adequate scoring method, photographs collected during boat based surveys can be used to effectively evaluate whale health in response to a changing ocean.