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Hieb, Elizabeth E.; Carmichael, Ruth Herrold; Aven, Allen; Nelson-Seely, Courtney; Taylor, Nicole
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2017 |
Sighting demographics of the West Indian manatee Trichechus manatus in the north-central Gulf of Mexico supported by citizen-sourced data.
Endangered Species Research 32(1): 321-332. 1 tab. 6 figs. https://doi.org/10.3354/esr00817 Apr. 7, 2017 (publ. online Jan. 2017).
–ABSTRACT: Traditional research methods are often limited in their ability to capture broad spatial and temporal changes in species distribution that affect global patterns of biodiversity. To provide range-wide demographic data needed to quantify and evaluate changes in habitat use and support ongoing recovery efforts for the endangered West Indian manatee Trichechus manatus, we analyzed data from a formal manatee sighting network that uses citizen-sourced data for the understudied north-central Gulf of Mexico region. Although historically considered to be outside manatees' typical US range, more than 1700 opportunistic, publicly reported manatee sightings and 23 mortalities have been documented in Alabama and Mississippi since the early 1900s. Live manatee sightings have occurred primarily during warmer months in rivers and subembayments. Manatee mortalities have significantly increased since the mid-1980s and have most often been attributed to cold stress, with 2 known mortalities due to vessel strikes in recent years. Sightings of individual manatees were most common, but group sizes of up to 17 were reported, typically in late summer. Decadal-scale trends in opportunistic sighting records demonstrate persistent spatial and temporal patterns of manatee occurrence in the north-central Gulf of Mexico and suggest greater use and importance of the region as seasonal manatee habitat than previously documented. If applied appropriately, citizen-sourced data have the potential to enhance targeted research efforts, significantly contribute to ecological datasets for a number of species, and provide a useful tool to enhance conservation and management.
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Cloyed, Carl S.; Hieb, Elizabeth E.; Collins, Merri K.; DaCosta, Kayla Page; Carmichael, Ruth H.
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2019 |
Linking use of ship channels by West Indian manatees (Trichechus manatus) to seasonal migration and habitat use.
Front. Mar. Sci. 6: 00318. doi: 10.3389/fmars.2019.00318. 5 tabs. 8 figs. + Suppl. material. June 12, 2019.
–ABSTRACT: Research on marine mammal occurrence in ship channels often focuses on large cetaceans in offshore shipping routes, while nearshore research largely addresses small vessel strikes. Marine mammals, such as the West Indian manatee, that reside in or migrate through nearshore areas, have potential to travel through a wide range of channel types, encountering a greater diversity of vessels than previously recognized. We tested the extent and conditions of ship channel use by manatees along the north-central Gulf of Mexico (nGoM) coast by combining data from telemetry-tracked individuals, opportunistic citizen-sourced sightings, and environmental attributes linked to manatee movements. Manatees used both nearshore boat channels (130 and 300 m wide) and open water fairways but used nearshore channels much more frequently, consistent with habitat requirements. Satellite-tracked individuals swam faster and moved more directly in all channel types, indicating use of these channels as migratory and travel corridors. Accordingly, generalized additive models revealed that manatees used channels most often during spring/early summer and fall and at temperatures coincidental with entry to and exit from the nGoM during migration. Manatees also occurred in ship channels when freshwater discharges were low, likely because timing of peak manatee occurrence in the nGoM coincides with seasonally low discharge periods. Expanding shipping activity world-wide is likely to increase interactions between marine mammals and a variety of vessel types, and these effects may be particularly impactful to migratory animals like manatees that use nearshore habitats at the interface of recreational boating and commercial shipping. Linking near- and offshore ship channel use to migration and habitat use will better aid risk-assessment for vessel collision and other shipping related activities for migratory marine species globally.
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Hieb, Elizabeth E.; Eniang, Edem A.; Keith-Diagne, Lucy W.; Carmichael, Ruth H.
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2021 |
Impacts of in-water bridge construction on manatees and implications for other marine megafauna species.
Journal of Wildlife Management 85(4): 674-685. 1 tab. 2 figs. DOI: 10.1002/jwmg.22030
–ABSTRACT: Globally, increasing coastal development requires construction and maintenance of transportation infrastructure that affects terrestrial and aquatic ecosystems. Construction of bridges as part of transportation networks introduces a series of risks to aquatic species near construction zones. We reviewed relevant literature and obtained exemplary case studies to synthesize potential effects of bridge construction on the West Indian manatee (Trichechus manatus), a nearshore megafauna species vulnerable to human activities. Stages of bridge construction including dredging, pile driving, and installation and assembly of bridge components each involve potential direct and indirect effects on manatees. Direct effects such as vessel interactions, entanglement or ingestion, and entrainment may result in acute physical injury or mortality. Indirect effects from construction such as habitat obstruction or degradation and increased noise from construction activities can alter behavior and intraspecies communication and reduce access to essential resources. Some effects of construction may be immediately diffcult to quantify, but cumulative effects through time can result in major habitat and species loss. To prevent large-scale negative effects of construction on manatees and other aquatic species, use and evaluation of itigation strategies should be implemented pre-, during, and post-construction. As the global human population increasingly occupies coastal zones, effective planning of coastal development, including bridge and other in-water construction, will be essential to support conservation and recovery efforts for manatees and other species at risk in these areas.
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Bibliography and Index of the Sirenia and Desmostylia 