scholarly journals High site-fidelity in common bottlenose dolphins despite low salinity exposure and associated indicators of compromised health

PLoS ONE ◽  
2021 ◽  
Vol 16 (9) ◽  
pp. e0258031
Author(s):  
Ryan Takeshita ◽  
Brian C. Balmer ◽  
Francesca Messina ◽  
Eric S. Zolman ◽  
Len Thomas ◽  
...  
Keyword(s):  
Bottlenose Dolphins ◽  
Satellite Telemetry ◽  
Skin Lesions ◽  
Estuarine System ◽  
Essential Information ◽  
Low Salinity ◽  
Health Assessments ◽  
Barataria Bay ◽  
High Site ◽  
Physiological Markers

More than 2,000 common bottlenose dolphins (Tursiops truncatus) inhabit the Barataria Bay Estuarine System in Louisiana, USA, a highly productive estuary with variable salinity driven by natural and man-made processes. It was unclear whether dolphins that are long-term residents to specific areas within the basin move in response to fluctuations in salinity, which at times can decline to 0 parts per thousand in portions of the basin. In June 2017, we conducted health assessments and deployed satellite telemetry tags on dolphins in the northern portions of the Barataria Bay Estuarine System Stock area (9 females; 4 males). We analyzed their fine-scale movements relative to modeled salinity trends compared to dolphins tagged near the barrier islands (higher salinity environments) from 2011 to 2017 (37 females; 21 males). Even though we observed different movement patterns among individual dolphins, we found no evidence that tagged dolphins moved coincident with changes in salinity. One tagged dolphin spent at least 35 consecutive days, and 75 days in total, in salinity under 5 parts per thousand. Health assessments took place early in a seasonal period of decreased salinity. Nonetheless, we found an increased prevalence of skin lesions, as well as abnormalities in serum biochemical markers and urine:serum osmolality ratios for dolphins sampled in lower salinity areas. This study provides essential information on the likely behavioral responses of dolphins to changes in salinity (e.g., severe storms or from the proposed Mid-Barataria Sediment Diversion project) and on physiological markers to inform the timing and severity of impacts from low salinity exposure.

scholarly journals Spatial and temporal variation in the occurrence of bottlenose dolphins in the Chesapeake Bay, USA, using citizen science sighting data

PLoS ONE ◽  
2021 ◽  
Vol 16 (5) ◽  
pp. e0251637
Author(s):  
Lauren Kelly Rodriguez ◽  
Amber D. Fandel ◽  
Benjamin R. Colbert ◽  
Jamie C. Testa ◽  
Helen Bailey
Keyword(s):  
Chesapeake Bay ◽  
Citizen Science ◽  
Marine Mammals ◽  
Generalized Additive Models ◽  
Bottlenose Dolphins ◽  
Temporal Distribution ◽  
Additive Models ◽  
Spatial And Temporal Variation ◽  
Estuarine System ◽  
Predictive Tool

Bottlenose dolphins (Tursiops truncatus) are migratory marine mammals that live in both open-ocean and coastal habitats. Although widely studied, little is known about their occurrence patterns in the highly urbanized estuary of the Chesapeake Bay, USA. The goal of this study was to establish the spatial and temporal distribution of bottlenose dolphins throughout this large estuarine system and use statistical modeling techniques to determine how their distribution relates to environmental factors. Three years (April-October 2017–2019) of dolphin sighting reports from a citizen-science database, Chesapeake DolphinWatch, were analyzed. The dolphins had a distinct temporal pattern, most commonly sighted during summer months, peaking in July. This pattern of observed occurrence was confirmed with systematic, passive acoustic detections of dolphin echolocation clicks from local hydrophones. Using spatially-exclusive Generalized Additive Models (GAM), dolphin presence was found to be significantly correlated to spring tidal phase, warm water temperature (24–30°C), and salinities ranging from 6–22 PPT. We were also able to use these GAMs to predict dolphin occurrence in the Bay. These predictions were statistically correlated to the actual number of dolphin sighting reported to Chesapeake DolphinWatch during that time. These models for dolphin presence can be implemented as a predictive tool for species occurrence and inform management of this protected species within the Chesapeake Bay.

scholarly journals Physiological Effects of Low Salinity Exposure on Bottlenose Dolphins (Tursiops truncatus)

2020 ◽  
Vol 1 (1) ◽  
pp. 61-75 ◽  
Author(s):  
Abby M. McClain ◽  
Risa Daniels ◽  
Forrest M. Gomez ◽  
Sam H. Ridgway ◽  
Ryan Takeshita ◽  
...  
Keyword(s):  
Medical Records ◽  
Tursiops Truncatus ◽  
Bottlenose Dolphins ◽  
Blood Samples ◽  
Low Salinity ◽  
Worldwide Distribution ◽  
Salinity Levels ◽  
Seawater Environment ◽  
Future Work ◽  
Free Ranging

Bottlenose dolphins (Tursiops truncatus) have a worldwide distribution in temperate and tropical waters and often inhabit estuarine environments, indicating their ability to maintain homeostasis in low salinity for limited periods of time. Epidermal and biochemical changes associated with low salinity exposure have been documented in stranded bottlenose dolphins; however, these animals are often found severely debilitated or deceased and in poor condition. Dolphins in the U.S. Navy Marine Mammal Program travel globally, navigating varied environments comparable to those in which free-ranging dolphins are observed. A retrospective analysis was performed of medical records from 46 Navy dolphins and blood samples from 43 Navy dolphins exposed to a variety of salinity levels for different durations over 43 years (from 1967–2010). Blood values from samples collected during low salinity environmental exposure (salinity ranging from 0–30 parts per thousand (ppt) were compared to samples collected while those same animals were in a seawater environment (31–35 ppt). Epidermal changes associated with low salinity exposure were also assessed. Significant decreases in serum sodium, chloride, and calculated serum osmolality and significant increases in blood urea nitrogen and aldosterone were observed in blood samples collected during low salinity exposure. Epidermal changes were observed in 35% of the animals that spent time in low salinity waters. The prevalence of epidermal changes was inversely proportional to the level of salinity to which the animals were exposed. Future work is necessary to fully comprehend the impacts of low salinity exposure in bottlenose dolphins, but the physiological changes observed in this study will help improve our understanding of the upper limit of duration and the lower limit of salinity in which a bottlenose dolphin can maintain homeostasis.

scholarly journals Health Assessments of Common Bottlenose Dolphins (Tursiops truncatus): Past, Present, and Potential Conservation Applications

2019 ◽  
Vol 6 ◽  
Author(s):  
Ashley Barratclough ◽  
Randall S. Wells ◽  
Lori H. Schwacke ◽  
Teresa K. Rowles ◽  
Forrest M. Gomez ◽  
...  
Keyword(s):  
Tursiops Truncatus ◽  
Bottlenose Dolphins ◽  
Health Assessments

Inconspicuous, recovering, or northward shift: status and management of the white shark (Carcharodon carcharias) in Atlantic Canada

2020 ◽  
Vol 77 (10) ◽  
pp. 1666-1677
Author(s):  
G. Bastien ◽  
A. Barkley ◽  
J. Chappus ◽  
V. Heath ◽  
S. Popov ◽  
...  
Keyword(s):  
Action Plan ◽  
Satellite Telemetry ◽  
White Shark ◽  
Conservation Priorities ◽  
Atlantic Canada ◽  
Telemetry Data ◽  
Carcharodon Carcharias ◽  
Proactive Management ◽  
High Site ◽  
Research Incentives

Although white sharks (Carcharodon carcharias) have been considered rare in Atlantic Canada waters, recent sighting records indicate a potentially increasing presence. We combine historical to present sighting data with satellite telemetry tracks of large juvenile and adult white sharks tagged in US (n = 9) and Atlantic Canada waters (n = 17) to show seasonal white shark presence and distribution in Atlantic Canada, returns by individuals over multiple years, and high site fidelity to the region. Telemetry data indicate that white sharks are a more common and consistent occurrence in Canadian waters than previously thought, presenting two potential scenarios: (i) tagging technology is revealing white shark presence that was historically cryptic and (or) (ii) a northward range expansion of white sharks in the Northwest Atlantic, potentially due to climate change, population recovery, and (or) increasing pinniped prey. Given combined sighting and telemetry data indicate a current need for proactive management of white sharks in Atlantic Canada waters, we propose the basis for a management action plan, addressing conservation priorities, management goals, and research incentives while considering the potential for human–shark interactions.

Response to Comment on Health of Common Bottlenose Dolphins (Tursiops truncatus) in Barataria Bay, Louisiana Following the Deepwater Horizon Oil Spill

2014 ◽  
Vol 48 (7) ◽  
pp. 4209-4211 ◽  
Author(s):  
Lori H. Schwacke ◽  
Cynthia R. Smith ◽  
Forrest I. Townsend ◽  
Randall S. Wells ◽  
Leslie B. Hart ◽  
...  
Keyword(s):  
Oil Spill ◽  
Tursiops Truncatus ◽  
Bottlenose Dolphins ◽  
Deepwater Horizon ◽  
Deepwater Horizon Oil Spill ◽  
Barataria Bay

scholarly journals Robust design capture-recapture analysis of abundance and demographic parameters of Indian River Lagoon common bottlenose dolphins (Tursiops truncatus truncatus)

2020 ◽  
Author(s):  
Wendy Noke Durden ◽  
Eric D. Stolen ◽  
Lydia Moreland ◽  
Elisabeth Howells ◽  
Teresa Jablonski ◽  
...  
Keyword(s):  
Robust Design ◽  
Tursiops Truncatus ◽  
Bottlenose Dolphins ◽  
Indian River Lagoon ◽  
Adult Survival ◽  
Demographic Parameters ◽  
Estuarine System ◽  
Mark Recapture ◽  
Temporary Emigration ◽  
Indian River

AbstractAccurate estimates of abundance are critical to species management and conservation. Common bottlenose dolphins (Tursiops truncatus truncatus) inhabiting the Indian River Lagoon (IRL) estuarine system along the east coast of Florida are impacted by anthropogenic activities and have had multiple unexplained mortality events, necessitating precise estimates of demographic and abundance parameters to implement management strategies. Mark-recapture methodology following a Robust Design survey was used to estimate abundance, adult survival, and temporary emigration for the IRL estuarine system stock of bottlenose dolphins. Models included a parameter (time since first capture) to assess evidence for transient individuals. Boat-based photo-identification surveys (n = 135) were conducted along predetermined contour and transect lines throughout the entire IRL (2016-2017). The best fitting model included the “transient” parameter to survival, allowed survival to vary by primary period, detection to vary by secondary session, and did not allow temporary emigration. Dolphin abundance ranged from 981 (95% CI: 882-1,090) in winter to 1,078 (95% CI: 968-1,201) in summer with a mean of 1,032 (95% CI: 969 -1,098). Model averaged seasonal survival rate for marked residents ranged from 0.85-1.00. Capture probability ranged from 0.20 to 0.42 during secondary sessions and transient rate from 0.06 to 0.07. This study represents the first Robust design mark-recapture survey effort to estimate abundance for IRL dolphins and provides parameter estimates to optimize sampling design of future studies. Transients included individuals with home ranges extending north of the IRL requiring further assessment of stock delineation. Results were remarkably similar to prior abundance estimates resulting from line-transect aerial surveys and were consistent with a stable population. Data will enable managers to evaluate the impact of fisheries-related takes as well as enable future comparisons of demographic parameters for a dolphin population that continues to sustain large scale mortality events and anthropogenic impacts.

Resighting and association patterns of bottlenose dolphins (Tursiops truncatus) in the Cedar Keys, Florida: insights into social organization

2001 ◽  
Vol 79 (3) ◽  
pp. 447-456 ◽  
Author(s):  
Ester Quintana-Rizzo ◽  
Randall S Wells
Keyword(s):  
Social Organization ◽  
Tursiops Truncatus ◽  
Bottlenose Dolphins ◽  
Aquatic Systems ◽  
Estuarine System ◽  
Association Patterns ◽  
Selective Pressures ◽  
The Social ◽  
Estuarine Systems ◽  
Common Dolphins

Little is known about the social organization of bottlenose dolphins (Tursiops truncatus) inhabiting open estuarine systems. Our purpose was to identify and quantify the resightings of bottlenose dolphins and associations formed among them to provide insights into the social organization of the species in the open estuarine system of the Cedar Keys, Florida. We conducted monthly photographic-identification surveys from June 1996 through May 1997. We identified a total of 233 dolphins of which 217 (93%) were classified into one of four categories based on the number of months in which they were sighted. "Rare" dolphins (sighted during 1–2 months) constituted more than half of these individuals (61%), followed by "occasional" (3–5 months; 20%), "common" (>8 months; 12%), and "frequent" (5–6 months; 7%) dolphins. We quantified the associations for dolphins sighted 10 times (26 common, 12 frequent, and 8 occasional) and found that individuals with different resighting patterns associate with each other but the association is mostly at a low level. The level of association among common dolphins, however, was higher within than between the sexes. Association patterns of common dolphins in the Cedar Keys resemble the associations of resident bottlenose dolphins inhabiting closed estuarine bays, suggesting that the selective pressures which induce such associations are the same in these aquatic systems.

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