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Runge, Michael C.; Langtimm, Catherine A.; Martin, Julien; Fonnesbeck, Christopher J.
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2012 |
Status and threats analysis for the Florida manatee (Trichechus manatus latirostris), 2012.
U.S. Geological Survey Open-File Report 2015–1083. DOI: 10.3133/ofr20151083.
–ABSTRACT: The endangered West Indian manatee (Trichechus manatus), especially the Florida subspecies (T. m. latirostris), has been the focus of conservation efforts and extensive research since its listing under the Endangered Species Act. On the basis of the best information available as of December 2012, the threats facing the Florida manatee were determined to be less severe than previously thought, either because the conservation efforts have been successful, or because our knowledge of the demographic effects of those threats is increased, or both. Using the manatee Core Biological Model, we estimated the probability of the Florida manatee population on either the Atlantic or Gulf coast falling below 500 adults in the next 150 years to be 0.92 percent. The primary threats remain watercraft-related mortality and long-term loss of warm-water habitat. Since 2009, however, there have been a number of unusual events that have not yet been incorporated into this analysis, including several severely cold winters, a severe red-tide die off, and substantial loss of seagrass habitat in Brevard County, Fla. Further, the version of the Core Biological Model used in 2012 makes a number of assumptions that are under investigation. A revision of the Core Biological Model and an update of this quantitative threats analysis are underway as of 2015.
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Martin, Julien; Edwards, Holly H.; Bled, Florent; Fonnesbeck, Christopher J.; Dupuis, Jérôme A.; Gardner, Beth; Koslovsky, Stacie M.; Aven, Allen M.; Ward-Geiger, Leslie I.; Carmichael, Ruth H.; Fagan, Daniel E.; Ross, Monica A.; Reinert, Thomas R.
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2014 |
Estimating upper bounds for occupancy and number of manatees in areas potentially affected by oil from the Deepwater Horizon oil spill.
PLoS ONE 9(3): e91683. 6pp. 1 tab. 2 figs. DOI: 10.1371/journal.pone.0091683. Mar. 26, 2014.
–ABSTRACT: The explosion of the Deepwater Horizon drilling platform created the largest marine oil spill in U.S. history. As part of the Natural Resource Damage Assessment process, we applied an innovative modeling approach to obtain upper estimates for occupancy and for number of manatees in areas potentially affected by the oil spill. Our data consisted of aerial survey counts in waters of the Florida Panhandle, Alabama and Mississippi. Our method, which uses a Bayesian approach, allows for the propagation of uncertainty associated with estimates from empirical data and from the published literature. We illustrate that it is possible to derive estimates of occupancy rate and upper estimates of the number of manatees present at the time of sampling, even when no manatees were observed in our sampled plots during surveys. We estimated that fewer than 2.4% of potentially affected manatee habitat in our Florida study area may have been occupied by manatees. The upper estimate for the number of manatees present in potentially impacted areas (within our study area) was estimated with our model to be 74 (95% CI 46 to 107). This upper estimate for the number of manatees was conditioned on the upper 95% CI value of the occupancy rate. In other words, based on our estimates, it is highly probable that there were 107 or fewer manatees in our study area during the time of our surveys. Because our analyses apply to habitats considered likely manatee habitats, our inference is restricted to these sites and to the time frame of our surveys. Given that manatees may be hard to see during aerial surveys, it was important to account for imperfect detection. The approach that we described can be useful for determining the best allocation of resources for monitoring and conservation.
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Martin, Julien; Edwards, Holly H.; Fonnesbeck, Christopher J.; Koslovsky, Stacie M.; Harmak, Craig W.; Dane, Teri M.
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2015 |
Combining information for monitoring at large spatial scales: First statewide abundance estimate of the Florida manatee.
Biological Conservation 186: 44-51. 4 figs. DOI: 10.1016/j.biocon.2015.02.029 June 2015.
–ABSTRACT: Monitoring abundance and distribution of organisms over large landscapes can be difficult. Because of challenges associated with logistics and data analyses uncorrected counts are often used as a proxy for abundance. We present the first statewide estimate of abundance for Florida manatees (Trichechus manatus latirostris) using an innovative approach that combines multiple sources of information. We used a combination of a double-observer protocol, repeated passes, and collection of detailed diving behavior data to account for imperfect detection of animals. Our estimate of manatee abundance was 6350 (95%CI: 5310–7390). Specifically, we estimated 2790 (95%CI: 2160–3540) manatees on the west coast (2011), and 3560 (95%CI: 2850–4410) on the east coast (2012). Unlike uncorrected counts conducted since 1991, our estimation method considered two major sources of error: spatial variation in distribution and imperfect detection. The Florida manatee is listed as endangered, but its status is currently under review; the present study may become important for the review process. Interestingly, we estimated that 70% (95%CI: 60–80%) of manatees on the east coast of Florida were aggregated in one county during our survey. Our study illustrates the value of combining information from multiple sources to monitor abundance at large scales. Integration of information can reduce cost, facilitate the use of data obtained from new technologies to increase accuracy, and contribute to encouraging coordination among survey teams from different organizations nationally or internationally. Finally, we discuss the applicability of our work to other conservation applications (e.g., risk assessment) and to other systems.
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Bibliography and Index of the Sirenia and Desmostylia 