Year
2025
Season
Fall
Paper Type
Master's Thesis
College
College of Arts and Sciences
Degree Name
Master of Science in Biology (MS)
Department
Biology
NACO controlled Corporate Body
University of North Florida. Department of Biology
Committee Chairperson
Dr. Quincy A. Gibson
Second Advisor
Dr. Eric G. Johnson
Third Advisor
Dr. Adam Rosenblatt
Department Chair
Dr. James Gelsleichter
College Dean
Dr. Kaveri Subrahmanyam
Abstract
Tamanend's bottlenose dolphins (Tursiops erebennus) in the St. Johns River (SJR), Jacksonville, FL, are subjected to substantial anthropogenic stressors (e.g., vessel traffic, dredging, fisheries interactions) and were heavily impacted by the 2013-2015 Mid-Atlantic cetacean morbillivirus unusual mortality event (UME). High prevalence of skin lesions and frequent sightings of emaciated dolphins suggest declining health and viability of the SJR dolphin community. Sighting data from Jul. 2011 to Oct. 2019 provided the rare opportunity to investigate long-term changes in dolphin abundance surrounding the UME. This study produced the first dolphin abundance estimate within the Jacksonville Estuarine System stock since 1997, and the first estimate and potential biological removal level for the SJR community. Following Pollock’s robust design, 33 primary periods with 96 secondary sessions were analyzed. Abundance and resighting data suggest that SJR residents consistently exhibit strong site fidelity, while seasonal residents display strong summer site fidelity. Total abundance estimates (adjusted for unmarked individuals) ranged from 147 individuals in winter 2019 (95% CI: 69–225) to 348 individuals in summer 2012 (95% CI: 290–419). The SJR has an exceptionally high dolphin density, ranging from 2.42 dolphins/km² in winter 2019 to 5.61 dolphins/km² in summer 2012. Survival rate and mean group size decreased significantly During-UME compared to Pre-UME. The probability of marked dolphins leaving the SJR During-UME was very low and typical seasonal emigration patterns did not occur. Although overall abundance did not change, these shifts in group size and emigration patterns highlight the long-term impacts of disease outbreaks on estuarine dolphin populations.
Suggested Citation
Wilkins, Allison L., "Long-term abundance estimates of a Northeast Florida estuarine dolphin community: Evaluating the impacts of the 2013–2015 Cetacean morbillivirus unusual mortality event" (2025). UNF Graduate Theses and Dissertations. 1373.
https://digitalcommons.unf.edu/etd/1373