West Florida Seagrass Beds IMMA
Size in Square Kilometres
15 288 km2
Qualifying Species and Criteria
Florida Manatee – Trichechus manatus latirostris
Criterion A; Criterion B (2)
Common bottlenose Dolphin – Tursiops truncatus
Criterion B (1)
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Summary
The west Florida Seagrass Beds IMMA extends along the west coast of Florida. It includes coastal waters up to the 10m contour line, as well as many bays and inlets and seagrass beds. Thermal basins, springs, creeks, dredged canals, and warm-water discharge sites of power plants, where waters typically remain above 20°C, are regularly visited by large numbers Endangered Florida manatees (Trichechus manatus latirostris), which also feed on the extensive seagrass beds in the IMMA. The area also hosts several small resident populations of bottlenose dolphins, many of which have been extensively studied for several decades. There are a variety of protected areas across the region, some designated specifically for protecting Florida manatees, including Manatee Park, Crystal River Wildlife Refuge, TECO power plant.
Description of Qualifying Criteria
Criterion A: Species or Population Vulnerability
The West Indian Manatee (Trichechus manatus) as a species has been listed as Endangered on the IUCN Red List of Threatened Species (Deutsch and Morales-Vela 2024). The Florida Manatee (Trichechus manatus latirostris) is a subspecies of the West Indian manatee that has not yet been assessed by the IUCN Red List.
Criterion B: Distribution and Abundance
Sub-criterion B1 – Small and Resident Populations
Several small and resident populations of common bottlenose dolphins (Tursiops truncatus) occur along Florida’s western/Gulf of Mexico coast. These form part of the “northern Gulf of Mexico bay, sound, and estuary stocks”, of which at least eight stocks are currently recognized by NOAA Fisheries: Waccasassa Bay/Withlacoochee Bay/Crystal Bay, St. Joseph Sound/Clearwater Harbor, Tampa Bay, Sarasota Bay/Little Sarasota Bay, Pine Island Sound/Charlotte Harbor/Gasparilla Sound/Lemon Bay, Caloosahatchee River, Estero Bay, and Chokosloskee Bay/Ten Thousand Islands/Gullivan Bay (NMFS, 2021). Long-term residency has been documented through extensive long-term photo identification studies in Tampa Bay (Wells, 1986; Urian et al., 2009), Sarasota Bay (Irvine and Wells, 1972; Wells, 1986; Scott et al., 1990), Lemon Bay (e.g., Bassos-Hull et al., 2013), and Charlotte Harbor/Pine Island Sound (Shane, 1990; Bassos-Hull et al., 2013). In Sarasota Bay, up to five concurrent generations have been identified through over more than four decades (Wells, 2014).
Sub-criterion B2: Aggregations
Aerial surveys to estimate abundance of manatees in Florida conducted in 2021-2022 (https://myfwc.com/research/manatee/research/population-monitoring/synoptic-surveys/) yielded an estimate of 9,790, of which 3,960-5,120 occurred on the west coast of Florida in the waters encompassed in this IMMA (Gowan et al., 2023). Manatees are vulnerable to cold stress, and their survival depends on the use of warm-water refuges resulting from discharge of power plants and passive thermal basins, springs, creeks, and dredged canals, particularly in inland freshwater bodies, and on the presence of seagrass meadows (Laist et al., 2013; Valade et al., 2020). Long-term monitoring through aerial surveys indicates the presence of large aggregations (50 to more than 500) of Florida manatees in four key wintering sites in the IMMA (Laist and Reynolds, 2005; Laist et al., 2013) including Crystal River, TECO power plant, and Manatee Park (Deutsch et al., 2003; Martin et al., 2015; Gowan et al., 2023). Along the coastline, extensive seagrass meadows provide the main feeding grounds for this species. Manatees primarily forage on Eelgrass (Halodule wrighti) and Syringodium filiforme, which are concentrated in intracoastal waters around the State, from Florida Bay to the Florida Panhandle along the Gulf Coast (Zieman & Zieman, 1989).
Supporting Information
Barros, N.B. and Wells, R.S., 1998. Prey and feeding patterns of resident bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida. Journal of Mammalogy, 79(3), pp.1045-1059.
Bassos-Hull, K., R.M. Perrtree, C.C. Shepard, S. Schilling, A.A. Barleycorn, J.B. Allen, B.C. Balmer, W.E. Pine and R.S. Wells. 2013. Long-term site fidelity and seasonal abundance estimates of common bottlenose dolphins (Tursiops truncatus) along the southwest coast of Florida and responses to natural perturbations. Journal of Cetacean Research and Management 13(1):19–30.
Deutsch, C.J. & Morales-Vela, B. 2024. Trichechus manatus. The IUCN Red List of Threatened Species 2024: e.T22103A43792740. https://dx.doi.org/10.2305/IUCN.UK.2024-2.RLTS.T22103A43792740.en. Accessed on 21 January 2025.
Gowan TA, Edwards HH, Krzystan AM, Martin J, Hostetler JA. 2023. 2021-2022 Statewide Abundance Estimates for the Florida Manatee. Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute Technical Report No. 27.
Irvine, B. and R.S. Wells. 1972. Results of attempts to tag Atlantic bottlenosed dolphins (Tursiops truncatus). Cetology 13:1–5.
Laist, D. W., & Reynolds III, J. E. (2005). Influence of power plants and other warm‐water refuges on Florida manatees. Marine Mammal Science, 21(4), 739-764.
Laist, D. W., Taylor, C., & Reynolds III, J. E. (2013). Winter habitat preferences for Florida manatees and vulnerability to cold. PLoS One, 8(3), e58978.
Martin, J., Edwards, H. H., Fonnesbeck, C. J., Koslovsky, S. M., Harmak, C. W., & Dane, T. M. (2015). Combining information for monitoring at large spatial scales: first statewide abundance estimate of the Florida manatee. Biological Conservation, 186, 44-51.
National Marine Fisheries Service, 2021. Common Bottlenose Dolphin (Tursiops truncatus truncatus): Northern Gulf of Mexico Bay, Sound, and Estuary Stocks. Marine Mammal Stock Assessment Reports by Species/Stock. https://www.fisheries.noaa.gov/s3/2023-08/Common-Bottlenose-Dolphin-Northern-Gulf-of-Mexico-Bay-Sound-and-Estuary-2022.pdf
Shane, S.H. 1990. Behavior and ecology of the bottlenose dolphin at Sanibel Island, Florida. Pages 245–265 in: S. Leatherwood and R.R. Reeves (eds.), The bottlenose dolphin. Academic Press, San Diego, CA.
Scott, M.D., R.S. Wells and A.B. Irvine. 1990. A long-term study of bottlenose dolphins on the west coast of Florida. Pages 235–244 in: S. Leatherwood and R.R. Reeves (eds.), The bottlenose dolphin. Academic Press, San Diego, CA.
Urian, K.W., S. Hofmann, R.S. Wells and A.J. Read. 2009. Fine-scale population structure of bottlenose dolphins (Tursiops truncatus) in Tampa Bay, Florida. Marine Mammal Science 25(3):619–638.
Valade, J., R. Mezich, K. Smith, M. Merrill and T. Calleson (editors). 2020 update. Florida Manatee Warm-Water Action Plan. U.S. Fish & Wildlife Service and Florida Fish and Wildlife Conservation Commission. 43pp.
Wells, R.S. 1986. Population structure of bottlenose dolphins: Behavioral studies along the central west coast of Florida. Contract report to NMFS, SEFSC. Contract No. 45-WCNF-5-00366. Available from: NMFS, Southeast Fisheries Science Center, 75 Virginia Beach Dr., Miami, FL 33149. 58 pp.
Wells, R. S. 2014. Social structure and life history of bottlenose dolphins near Sarasota Bay, Florida: Insights from four decades and five generations. Pages 149–172 in: J. Yamagiwa and L. Karczmarski (eds.), Primates and cetaceans: Field research and conservation of complex mammalian societies. Primatology Monographs. Springer Japan, Tokyo.
Zieman, J.C. and Zieman, R.T., 1989. The ecology of the seagrass meadows of the west coast of Florida: a community profile (Vol. 85, No. 7). US Department of the Interior, Fish and Wildlife Service, Research and Development.
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