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Bacchus, Marie-Lys; Dunbar, Stephen C.; Self-Sullivan, Caryn
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2009 |
Characterization of resting holes and their use by the Antillean manatee (Trichechus manatus manatus) in the Drowned Cayes, Belize.
Aquatic Mammals
35(1): 62-71.
–Abstract: In the Drowned Cayes area of Belize, manatees (Trichechus manatus manatus) are commonly observed resting in depressions in the substrate, locally referred to as manatee resting holes. To understand why manatees prefer locations with resting holes, the physical and environmental attributes of the depressions were characterized and diurnal and nocturnal use by manatees at four resting hole sites were documented over two summers. Twelve resting hole sites were compared with 20 non-resting hole sites in the Drowned Cayes, using water depth, substrate type, vegetation, water velocity, salinity, and water temperature. Four resting holes were chosen for repeated diurnal and nocturnal observations, during which sea and weather conditions were recorded in addition to the presence/absence of manatees. Resting holes were significantly deeper and had slower surface water velocity than areas without resting holes. A total of 168 point scans were conducted over 55 d, resulting in 39 manatee sightings over two summers. There was a significant difference in the number of sightings between research years and between day and night scans. Given the large number of resting holes in the Drowned Cayes, many of which are in sheltered areas with slow currents, it is possible that manatees select these spots based on the tranquility of the water and environment. The combination of slow currents, protection from waves, low numbers of boats, and nearby seagrass beds would make these ideal resting areas. These findings have implications for the conservation of important manatee habitat. DOI 10.1578/AM.35.1.2009.62
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Appeltans, Ward; 120 other authors including Domning, Daryl Paul; Self-Sullivan, Caryn
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2012 |
The magnitude of global marine species diversity.
Current Biology
22(23): 2189-2202. 2 tabs. 3 figs. http://dx.doi.org/10.1016/j.cub.2012.09.036 Dec. 4, 2012 (publ. online Nov. 15, 2012).
–Notice: Nature 491: 498, Nov. 22, 2012.
Includes as Supplemental Information two tables and Supplemental Experimental Procedures (available online at http://dx.doi.org/10.1016/j.cub.2012.09.036).
Sirenia mentioned on pp. 2195 and 2197, and in Supplemental Table S2.
Summary: Background: The question of how many marine species exist is important because it provides a metric for how much we do and do not know about life in the oceans. We have compiled the first register of the marine species of the world and used this baseline to estimate how many more species, partitioned among all major eukaryotic groups, may be discovered. Results: There are ~226,000 eukaryotic marine species described. More species were described in the past decade (~20,000) than in any previous one. The number of authors describing new species has been increasing at a faster rate than the number of new species described in the past six decades. We report that there are ~170,000 synonyms, that 58,000–72,000 species are collected but not yet described, and that 482,000–741,000 more species have yet to be sampled. Molecular methods may add tens of thousands of cryptic species. Thus, there may be 0.7–1.0 million marine species. Past rates of description of new species indicate there may be 0.5 ± 0.2 million marine species. On average 37% (median 31%) of species in over 100 recent field studies around the world might be new to science. Conclusions: Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century.
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LaCommare, Katherine S.; Brault, Solange; Self-Sullivan, Caryn; Hines, Ellen M.
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2012 |
Trend detection in a boat-based method for monitoring sirenians: Antillean manatee case study.
Biological Conservation
152:169-177. 2 tables. 4 figures. DOI: 10.1016/j.biocon.2012.02.021. August 2012.
–ABSTRACT: Accurate monitoring is a critical step in evaluating the conservation and management needs of endangered species. We evaluated a low cost, effective survey method for monitoring West Indian manatees (Trichechus manatus manatus) in Belize, Central America. The objectives for this paper are (1) to evaluate a count-based population index derived from a boat-based survey method, (2) to examine trends in manatee abundance in the Drowned Cayes area, (3) to conduct a power analysis to explore our ability to detect a trend and the ramifications of survey structure on trend detection. We used a generalized linear model to evaluate the impact of environmental conditions on sighting probability and to determine whether the number of manatees observed per 20-min scan changed from 2001 to 2007. We used simulations to determine statistical power – the ability to detect potential declines of 10%, 25% or 50% over 15 years and for various sampling regimes. The number of manatees sighted per scan was not affected by sighting conditions. There was no change in the mean number of manatees sighted per scan from 2001 to 2007. Our ability to detect a trend ranged from 9% to 100% depending on the level of decline, scan duration, number of points surveyed and number of surveys. This survey protocol is a practical and repeatable way to examine population trends of sirenians in similar habitats around the world.
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Bibliography and Index of the Sirenia and Desmostylia 