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O'Shea, Thomas J.; Langtimm, Catherine A.
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1995 |
Estimation of survival of adult Florida manatees in the Crystal River, at Blue Spring, and on the Atlantic coast. In: T. J. O'Shea, B. B. Ackerman, & H. F. Percival (eds.), Population biology of the Florida manatee (q.v.).
Information & Technology Rept. (U.S. Dept. Interior, Natl. Biological Service) (vi + 289) 1: 194-222. 9 tabs. 3 figs. 1 app. Aug. 1995.
–Abstr. in O'Shea et al. (1992: 21). Application of Cormack-Jolly-Seber open population models to manatee photoidentification databases and radiotelemetry studies indicated that survival at Crystal River and Blue Spring may be high enough for population growth, while the Atlantic Coast population may be in decline. Adult survivorship seemed to be constant with age in all three study groups.
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Langtimm, Catherine A.; O'Shea, Thomas J.; Pradel, R.; Beck, Cathy A.
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1998 |
Estimates of annual survival probabilities for adult Florida manatees (Trichechus manatus latirostris).
Ecology 79(3): 981-997. 5 tabs. 5 figs.
–Using a mark-recapture approach based on the manatee photo-identification database, adult survival probabilities were found to be high and constant at Crystal River and Blue Spring, but significantly lower and variable on the Atlantic coast. Survival did not differ between sexes, nor was evidence of senescence detected.
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Martin, Julien; Fackler, Paul L.; Nichols, James D.; Lubow, Bruce C.; Eaton, Mitchell J.; Runge, Michael C.; Stith, Bradley M.; Langtimm, Catherine A.
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2011 |
Structured decision making as a proactive approach to dealing with sea level rise in Florida.
Climate Change 107(1-2): 185-202. 5 figs. DOI:10.1007/s10584-011-0085-x. July 2011.
–ABSTRACT: Sea level rise (SLR) projections along the coast of Florida present an enormous challenge for management and conservation over the long term. Decision makers need to recognize and adopt strategies to adapt to the potentially detrimental effects of SLR. Structured decision making (SDM) provides a rigorous framework for the management of natural resources. The aim of SDM is to identify decisions that are optimal with respect to management objectives and knowledge of the system. Most applications of SDM have assumed that the managed systems are governed by stationary processes. However, in the context of SLR it may be necessary to acknowledge that the processes underlying managed systems may be non-stationary, such that systems will be continuously changing. Therefore, SLR brings some unique considerations to the application of decision theory for natural resource management. In particular, SLR is expected to affect each of the components of SDM. For instance, management objectives may have to be reconsidered more frequently than under more stable conditions. The set of potential actions may also have to be adapted over time as conditions change. Models have to account for the non-stationarity of the modeled system processes. Each of the important sources of uncertainty in decision processes is expected to be exacerbated by SLR. We illustrate our ideas about adaptation of natural resource management to SLR by modeling a non-stationary system using a numerical example. We provide additional examples of an SDM approach for managing species that may be affected by SLR, with a focus on the endangered Florida manatee.
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Stith, Bradley M.; Reid, James P.; Langtimm, Catherine A.; Swain, Eric D.; Doyle, Terry J.; Slone, Daniel H.; Decker, Jeremy D.; Soderqvist, Lars E.
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2011 |
Temperature inverted haloclines provide winter warm-water refugia for manatees in southwest Florida.
Estuaries & Coasts 34(1): 106-119. 2 tabs. 11 figs. DOI 10.1007/s12237-010-9286-1 Published online April 21, 2010.
–ABSTRACT: Florida manatees (Trichechus manatus latirostris) overwintering in the Ten Thousand Islands and western Everglades have no access to power plants or major artesian springs that provide warm-water refugia in other parts of Florida. Instead, hundreds of manatees aggregate at artificial canals, basins, and natural deep water sites that act as passive thermal refugia (PTR). Monitoring at two canal sites revealed temperature inverted haloclines, which provided warm salty bottom layers that generally remained above temperatures considered adverse for manatees. At the largest PTR, the warmer bottom layer disappeared unless significant salt stratification was maintained by upstream freshwater inflow over a persistent tidal wedge. A detailed three-dimensional hydrology model showed that salinity stratification inhibited vertical convection induced by atmospheric cooling. Management or creation of temperature inverted haloclines may be a feasible and desirable option for resource managers to provide passive thermal refugia for manatees and other temperature sensitive aquatic species.
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Kendall, William L.; White, Gary C.; Hines, James E.; Langtimm, Catherine A.; Yoshizaki, Jun
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2012 |
Estimating parameters of hidden Markov models based on marked individuals: use of robust design data.
Ecology 93(4): 913-920. 2 tabs. 2 figs. DOI: 10.1890/111538.1. April 2012.
–ABSTRACT: Development and use of multistate mark–recapture models, which provide estimates of parameters of Markov processes in the face of imperfect detection, have become common over the last 20 years. Recently, estimating parameters of hidden Markov models, where the state of an individual can be uncertain even when it is detected, has received attention. Previous work has shown that ignoring state uncertainty biases estimates of survival and state transition probabilities, thereby reducing the power to detect effects. Efforts to adjust for state uncertainty have included special cases and a general framework for a single sample per period of interest. We provide a flexible framework for adjusting for state uncertainty in multistate models, while utilizing multiple sampling occasions per period of interest to increase precision and remove parameter redundancy. These models also produce direct estimates of state structure for each primary period, even for the case where there is just one sampling occasion. We apply our model to expected-value data, and to data from a study of Florida manatees, to provide examples of the improvement in precision due to secondary capture occasions. We have also implemented these models in program MARK. This general framework could also be used by practitioners to consider constrained models of particular interest, or to model the relationship between within-primary-period parameters (e.g., state structure) and between-primary-period parameters (e.g., state transition probabilities).
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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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Stith, Bradley M.; Slone, D. H.; De Wit, Martine; Edwards, Holly H.; Langtimm, Catherine A.; Swain, E. D.; Soderqvist, L. E.; Reid, James P.
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2012 |
Passive thermal refugia provided warm water for Florida manatees during the severe winter of 2009-2010.
Marine Ecology Progress Series 462: 287-301. DOI:10.3354/meps09732. Aug. 21, 2012.
–ABSTRACT: Haloclines induced by freshwater inflow over tidal water have been identified as an important mechanism for maintaining warm water in passive thermal refugia (PTR) used by Florida manatees Trichechus manatus latirostris during winter in extreme southwestern Florida. Record-setting cold during winter 2009-2010 resulted in an unprecedented number of manatee deaths, adding to concerns that PTR may provide inadequate thermal protection during severe cold periods. Hydrological data from 2009-2010 indicate that 2 canal systems in the Ten Thousand Islands (TTI) region acted as PTR and maintained warm bottom-water temperatures, even during severe and prolonged cold periods. Aerial survey counts of live and dead manatees in TTI during the winter of 2009-2010 suggest that these PTR were effective at preventing mass mortality from hypothermia, in contrast to the nearby Everglades region, which lacks similar artificial PTR and showed high manatee carcass counts. Hydrological data from winter 2008-2009 confirmed earlier findings that without haloclines these artificial PTR may become ineffective as warm-water sites. Tidal pumping of groundwater appears to provide additional heat to bottom water during low tide cycles, but the associated thermal inversion is not observed unless salinity stratification is present. The finding that halocline-driven PTR can maintain warm water even under extreme winter conditions suggests that they may have significant potential as warm-water sites. However, availability and conflicting uses of freshwater and other management issues may make halocline-driven PTR unreliable or difficult to manage during winter.
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Peñaloza, Claudia L.; Kendall, William L.; Langtimm, Catherine A.
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2014 |
Reducing bias in survival under nonrandom temporary emigration.
Ecological Applications 24(5): 1155–1166. 3 tabs. 2 figs. 1 pl. DOI:10.1890/13-0558.1. July 2014.
–ABSTRACT: Despite intensive monitoring, temporary emigration from the sampling area can induce bias severe enough for managers to discard survival parameter estimates toward the terminus of the times series (terminal bias). Under random temporary emigration, unbiased parameters can be estimated with CJS models. However, unmodeled Markovian temporary emigration causes bias in parameter estimates, and an unobservable state is required to model this type of emigration. The robust design is most flexible when modeling temporary emigration, and partial solutions to mitigate bias have been identified; nonetheless, there are conditions were terminal bias prevails. Long-lived species with high adult survival and highly variable nonrandom temporary emigration present terminal bias in survival estimates, despite being modeled with the robust design and suggested constraints. Because this bias is due to uncertainty about the fate of individuals that are undetected toward the end of the time series, solutions should involve using additional information on survival status or location of these individuals at that time. Using simulation, we evaluated the performance of models that jointly analyze robust design data and an additional source of ancillary data (predictive covariate on temporary emigration, telemetry, dead recovery, or auxiliary resightings) in reducing terminal bias in survival estimates. The auxiliary resighting and predictive covariate models reduced terminal bias the most. Additional telemetry data were effective at reducing terminal bias only when individuals were tracked for a minimum of two years. High adult survival of long-lived species made the joint model with recovery data ineffective at reducing terminal bias because of small-sample bias. The naïve constraint model (last and penultimate temporary emigration parameters made equal), was the least efficient, although still able to reduce terminal bias when compared to an unconstrained model. Joint analysis of several sources of data improved parameter estimates and reduced terminal bias. Efforts to incorporate or acquire such data should be considered by researchers and wildlife managers, especially in the years leading up to status assessments of species of interest. Simulation modeling is a very cost-effective method to explore the potential impacts of using different sources of data to produce high-quality demographic data to inform management.
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Runge, Michael C.; Sanders-Reed, Carol A.; Langtimm, Catherine A.; Hostetler, J. A.; Martin, Julien; Deutsch, Charles J.; Ward-Geiger, Leslie I.; Mahon, Gary L.
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2017 |
Status and threats analysis for the Florida manatee (Trichechus manatus latirostris), 2016.
U.S. Geological Survey Scientific Investigations Report 2017-5030: ix + 40. 8 tabs. 18 figs. https://doi.org/10.3133/sir20175030
–ABSTRACT: Trichechus manatus (West Indian manatee), especially T. m. latirostris, the Florida subspecies, has been the focus of conservation efforts and extensive research since its listing under the Endangered Species Act of 1973. To determine the status of, and severity of threats to, the Florida manatee, a comprehensive revision and update of the manatee Core Biological Model was completed and used to perform a population viability analysis for the Florida manatee. The probability of the Florida manatee population falling below 500 adults on either the Gulf or East coast within the next 100 years was estimated to be 0.42 percent. This risk of quasi-extinction is low because the estimated adult survival rates are high, the current population size is greater than 2,500 on each coast, and the estimated carrying capacity for manatees is much larger than the current abundance estimates in all four regions of Florida. Three threats contribute in roughly equal measures to the risk of quasi-extinction: watercraft-related mortality, red-tide mortality, and loss of warm-water habitat. Only an increase in watercraft-related mortality has the potential to substantially increase the risk of quasi-extinction at the statewide or coastal level. Expected losses of warm-water habitat are likely to cause a major change in the distribution of the population from the regions where manatees rely heavily on power plant effluents for warmth in winter (Southwest and Atlantic regions) to the regions where manatees primarily use natural springs in winter (Northwest and Upper St. Johns regions). The chances are nearly 50 percent that manatee populations in the Southwest and Atlantic regions will decrease from their 2011 levels by at least 30 percent over the next century.
A large number of scenarios were examined to explore the possible effects of potential emerging threats, and in most of them, the risk of quasi-extinction at the coastal scale within 100 years did not rise above 1 percent. The four exceptions are scenarios in which the rate of watercraft-related mortality increases, carrying capacity is only a fraction of the current estimates, a new chronic source of mortality emerges, or multiple threats emerge in concert. Even in these scenarios, however, the risk of falling below 500 adults on either the East coast or the Gulf coast within 100 years from 2011 is less than 10 percent. High adult survival provides the population with strong resilience to a variety of current and future threats. On the basis of these analyses, we conclude that if these threats continue to be managed effectively, manatees are likely to persist on both coasts of Florida and remain an integral part of the coastal Florida ecosystem through the 21st century. If vigilance in management is reduced, however, the scenarios in which manatees could face risk of decline become more likely.
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Bibliography and Index of the Sirenia and Desmostylia 