Publication Details
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Quantifying injury to common bottlenose dolphins from the Deepwater Horizon oil spill using an age-, sex- and class-structured population model
Author(s): Schwacke, L.H.; L. Thomas; R.S. Wells; W.E. McFee; A.A. Hohn; K.D. Mullin; E.S. Zolman; B.M. Quigley; T.K. Rowles; J.H. Schwacke
NCCOS Center: HML
Publication Type: Journal Article
Journal Title: Endangered Species Research
Date of Publication: 2017
Reference Information: 33
265-279
Keywords: population model; Monte Carlo analysis; survival; density dependence; Bayesian model; Deepwater Horizon; impact assessment; cetacean
Abstract: Field studies documented increased mortality, adverse health effects, and reproductive failure in common bottlenose dolphins (Tursiops truncatus) following the Deepwater Horizon (DWH) oil spill. In order to determine the appropriate type and amount of restoration needed to compensate for losses, the overall extent of injuries to dolphins had to be quantified. Simply counting dead individuals is inadequate because it does not consider long-term impacts to populations, such as the loss of future reproductive potential from mortality of females, or the chronic health effects that continue to compromise survival long after acute effects subside. A sex- and age-structured model of population growth with additional class structure to represent dolphins exposed and unexposed to DWH oil was constructed. The model was applied for stocks along the northern Gulf of Mexico coast to predict injured population trajectories using estimates of post-spill survival and reproductive rates. Injured trajectories were compared to baseline trajectories that were expected had the DWH incident not occurred. For the dolphin stock in Barataria Bay, Louisiana the difference between the baseline and injured population size summed over the entire modeled time period, termed Lost Cetacean Years (LCY), was substantial with an estimated 30,347 LCY (95% CI = 11,511 - 89,746) . The model predicts that it will take 39 years (95% CI = 24-80) for the Barataria Bay stock to recover to baseline and similar recovery timelines were predicted for stocks in the Mississippi River Delta, Mississippi Sound, and Mobile Bay as well as for the Northern Coastal Stock.
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