Freshwater Exposure, Successful Relocation and Subsequent Drowning of a Subadult Atlantic Bottlenose Dolphin (Tursiops truncatus)
In cetaceans, prolonged exposure to low salinity water (>5 days, <5ppt) causes skin lesions, corneal edema, and electrolyte abnormalities. Here we review a case of a subadult Atlantic bottlenose dolphin that refused to leave a freshwater lake in Seminole, Alabama. The animal was observed in the lake for 1 month (24 Feb to 25 Mar 2016) and was then relocated to a nearby brackish water bay (15–25 ppt) in Orange Beach, Alabama because the animal had begun to develop freshwater skin lesions and corneal opacities.
Blood samples and skin biopsies collected during the rescue revealed abnormalities consistent with prolonged freshwater exposure including decreased sodium, chloride and low osmolality. Twelve weeks following successful relocation, the dolphin was found dead with signs of fishery interaction. Necropsy showed resolution of freshwater skin lesions and normal sodium, potassium and osmolality; however, the corneal opacities had worsened. This case highlights the cumulative effects of natural and anthropogenic pressures on dolphins in Alabama and provides a unique opportunity to follow the effects of 1 month of freshwater exposure followed by 3 months of recovery.
In this Alabama watershed, there are seasonal salinity fluctuations and anthropogenic pressures, such as fishery interactions, that commonly impact the resident dolphins. Urbanization or climate variations may enhance freshwater runoff and increase human water activities, such as fishing. This case shows the synergistic effects of these influences, and provides information on prolonged freshwater exposure, subsequent recovery and sequelae.
Rescue and monitoring were conducted with the assistance of Emerald Coast Wildlife Refuge, Institute for Marine Mammal Studies, NOAA-NMFS, Sarasota Dolphin Research Program, SeaWorld Orlando Rescue Team, University of Central Florida and University of South Alabama. Reporting, monitoring and tracking assistance was provided by Alabama Department of Conservation and Natural Resources, City of Orange Beach, and Orange Beach area dolphin tour boat operators. We thank Katie Witlicki for her hard work associated with this case. Photos courtesy of ALMMSN, Brandon Ard, Elise Poche, David Rotstein & Christina Toms. Stranding network funding was provided by the National Fish & Wildlife Foundation and the Alabama Department of Conservation and Natural Resources.
* Presenting author
+ Student presenter
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