Analysis of Stranding Data to Support Estimates of Human-Caused Mortality and Serious Injury in Common Bottlenose Dolphin (Tursiops Truncatus Truncatus) Stock Assessments for the Atlantic Ocean and Gulf of Mexico

Maze-Foley, Katherine; Byrd, Barbie L.; Horstman, Stacey C.; Powell, Jessica R.

doi:10.25923/jt1x-jv75

Cited by 2 publications

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“…Had we not normalized data by area of shoreline for each state or considered the effects of effort through time, it is likely the substantial increase in HI-related strandings in an area of relatively small shoreline like Alabama or the Florida panhandle (compared to all of Florida) would be overlooked. Of note, the types of HI-positive Frontiers in Environmental Science frontiersin.org strandings in Alabama represent the wide range of HI types, which are often described but rarely quantified in publications, for bottlenose dolphin strandings in U.S. waters (Samuels and Bejder, 2004;Byrd et al, 2014;Vail, 2016;Powell et al, 2018;Maze-Foley et al, 2019;Collins et al, 2020), further emphasizing the broad nature of HI in this local area. Our analytical approach provides a method for other researchers to similarly evaluate anthropogenic impacts, including historical assessment of response effort, on marine mammal strandings and identify areas of high occurrence for other species and geographical locations.…”

Section: Discussionmentioning

confidence: 99%

Human influence on bottlenose dolphin (Tursiops truncatus) strandings in the northern Gulf of Mexico

Carmichael

Hodanbosi

Russell

et al. 2022

Front. Environ. Sci.

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Human activity affects marine mammal stranding rates in two major ways; through human interaction (HI) that may lead to mortality and through search and response efforts that enable carcass detection. To better quantify the combined effects of these interacting human influences, we analyzed strandings for bottlenose dolphins (Tursiops truncatus) in the northern Gulf of Mexico (nGOM), an area of high cetacean strandings. To identify hotspots of human influence, we first determined the number of total and HI-related bottlenose dolphin strandings normalized to shoreline length in each nGOM U.S. state, which represent major response areas. To estimate the effects of response effort on stranding numbers (for HI and non-HI strandings), we used the Deepwater Horizon oil spill (DWHOS) as an established benchmark to compare periods of lower (pre-spill) and higher (post-spill) response effort. Strandings in Alabama waters were used as a case study to detail spatial and temporal variation due to human influences during the 39-year period of retrospective study. We found an increase in strandings from Louisiana through Alabama following the DWHOS. Non-oil related HI strandings increased in total number in AL, and they increased as a proportion of total strandings in Alabama (16%) and the Florida panhandle (12%). The increase in HI-related strandings in Alabama was driven by mortality of many types, but particularly fishery interactions and cases of apparent intentional harm. The Alabama case study clearly detected lower stranding numbers during periods of low or intermittent response coverage. Our findings are consistent with an overall increase in stranding numbers due to a combination of increased stranding occurrence and response effort following the DWHOS. Importantly, we provide evidence that HI-related standings increased independently from the DWHOS, with ongoing increases in at least one hotspot (Alabama). These findings provide a first step to parsing out different effects of human influences on stranding data for a common coastal cetacean. Our approach establishes baselines for future damage and recovery assessments, identifies areas where resources can be focused for management and education, and highlights the power of response and monitoring agencies to positively influence stranding datasets.

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Section: Discussionmentioning

confidence: 99%

Human influence on bottlenose dolphin (Tursiops truncatus) strandings in the northern Gulf of Mexico

Carmichael

Hodanbosi

Russell

et al. 2022

Front. Environ. Sci.

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“…To quantify spatial clustering of stranded bottlenose dolphin events, we followed the stock boundaries delineated by Maze-Foley et al (2019) for use in quantifying human impacts to NMFS bottlenose dolphin stocks. The spatial boundaries for Texas bottlenose dolphin stocks consisted of eight polygons -7 polygons represented bottlenose dolphin BSE stocks (Sabine Lake, Galveston Bay/East Bay/Trinity Bay, West Bay, Matagorda Bay/Tres Palacios Bay/Lavaca Bay, Copano Bay/Aransas Bay/San Antonio Bay/Redfish Bay/Espiritu Santo Bay, Nueces Bay/Corpus Christi Bay, and Laguna Madre) and 1 polygon represented the Western GoM Coastal Stock (Fig.…”

Section: Spatial Analysismentioning

confidence: 99%

Forty-year historical analysis of marine mammal strandings in Texas, from 1980 – 2019

Piwetz

Ronje

Whitehead

2022

JCRM

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Long-term trends in marine mammal stranding patterns can provide useful information on basic life history parameters, spatiotemporal distribution, natural and human-related mortality events, and potentially vulnerable populations. Between 1980 and 2019, a total of 5,301 marine mammal strandings were recorded in Texas, USA. In total, 23 species were identified, including 19 odontocete species (toothed whales and dolphins), 3 mysticete species (baleen whales), and 1 sirenian species (manatee). Common bottlenose dolphins (Tursiops truncatus) stranded most frequently (94%). Six unusual mortality events occurred with causes attributed to disease, harmful algal blooms, or unknown etiologies. Common bottlenose dolphin stranding events increased significantly in late winter/early spring, with an early onset in southern Texas, and had a consistent peak in March involving primarily calves and adults. Spatial analyses using kernel density estimation within seven coastal Texas stock management areas, delineated by the National Marine Fisheries Service, identified potential hotspots for common bottlenose dolphin strandings near higher human population density and deep water channels. Peak stranding density estimates in each stock area ranged from 0.32 – 4.6km-2 for presumed bay, sound and estuarine (BSE) stocks and 0.82km-2 for the presumed Western Gulf of Mexico Coastal Stock. Common bottlenose dolphin stranding events were positively male-biased, including a significantly higher number of stranded male fetuses and neonates, and sexual dimorphism was observed in total body length of adults, with significantly greater length in males. For all records where human interaction (HI) could be determined as ‘yes’ or ‘no’, 30% were positive for HI, with the highest proportion of HI events occurring in the central and southern-most BSE stock areas; however, it is unknown how many HI cases contributed to mortality. This longitudinal study provides a comprehensive overview of marine mammal stranding patterns in Texas and serves as a useful resource for stranding investigators and Gulf-wide natural resource managers.

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Analysis of Stranding Data to Support Estimates of Human-Caused Mortality and Serious Injury in Common Bottlenose Dolphin (Tursiops Truncatus Truncatus) Stock Assessments for the Atlantic Ocean and Gulf of Mexico

Cited by 2 publications

References 0 publications

Human influence on bottlenose dolphin (Tursiops truncatus) strandings in the northern Gulf of Mexico

Human influence on bottlenose dolphin (Tursiops truncatus) strandings in the northern Gulf of Mexico

Forty-year historical analysis of marine mammal strandings in Texas, from 1980 – 2019

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