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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 theDeepwater Horizonoil 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.

Poster created and presented in 2012 Abstract Species occurrence data collected by citizen volunteers or mined from historical records can supplement species distribution studies by adding dimensions of spatial and temporal survey coverage that may not be cost-effective or even possible for researchers to obtain otherwise. In the absence of rigorous survey or quality assurance methods, most citizen-collected or historic occurrence data may be biased in space to favor human population centers: species in areas of high human activity may be oversampled, while species in relatively unpopulated areas may not be adequately accounted for. We gathered citizen-reported occurrence data for the West Indian manatee (Trichechus manatus) in coastal Alabama (AL), USA from 2007 to 2012. We found significant differences in spatial distribution between citizen-reported sightings and reference locations derived from GPS tag data from six manatees in the study area. To correct for potential spatial biases in the citizen-reported dataset, we weighted each sighting report using a) population density of closest US Census block (2010), and b) aquatic distance to closest boat ramp. After correcting for spatial bias, the spatial distribution of citizen-reported sightings was closer to reference GPS locations. These results provided a foundation to enhance our knowledge of manatee distribution in AL by supplementing GPS tag data with unbiased sighting report data not explicitly detected by GPS tags, such as manatee group size and behavior. These results demonstrate that species occurrence data collected under different methodologies may be corrected and integrated to form a more robust depiction of location and movement patterns for the species being surveyed.