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Maryland Baseline Studies: Sea Turtles
Maryland Baseline Studies: Sea Turtles

Five species of sea turtles occur in the Mid-Atlantic United States, all of which are listed as Threatened or Endangered under the Endangered Species Act. They were a focus of this study, in part, because few turtles occur in European waters (where most offshore wind energy development has occurred to date), and the effects of this type of development on sea turtles remain poorly understood.

Download Wildlife Studies Offshore of Maryland. This 8-page summary publication represents an overview of results from the final technical report for the Maryland-focused study, and features survey results and case studies on marine mammals, sea turtles, and wintering seabirds. The Executive Summary for the technical report is also available here.

Additional results and case studies can be found in the 32-page synthesis report for the mid-Atlantic regional study, Mid-Atlantic Wildlife Studies: Distribution and Abundance of Wildlife along the Eastern Seaboard, 2012-2014.

 

Take Home Messages

  • There was substantial overlap between sea turtle distributions and areas of planned offshore wind development, particularly during autumn and in southern sections of the regional study area.
  • Digital aerial surveys seem to have higher detection rates of sea turtles than other survey approaches, but application of newer technologies with improved species differentiation is needed.
 

Background

Turtles are long-lived animals with worldwide oceanic distribution. The five species that occur in our study area are the Loggerhead Sea Turtle, Leatherback Sea Turtle, Kemp’s Ridley Sea Turtle, Hawksbill Sea Turtle, and Green Sea Turtle. All are listed as Threatened or Endangered under the Endangered Species Act. Adults migrate seasonally, and sea turtles' body temperatures vary considerably with their environment, limiting them to waters in specific temperature ranges.

The mid-Atlantic region has large populations of a high diversity of turtles, but there are many existing threats that could cause population declines. These include mortality from bycatch in fishing nets, collisions with vessels, especially those traveling at high speeds, loss of nesting habitat to coastal development, and disturbance or destruction of nests by humans or other animals. Potential concerns from offshore wind energy development include the effects of noise from seismic profiling, pile driving, and trenching.

 

Survey Methods

Turtles were more frequently observed in digital aerial surveys than in boat surveys, likely in large part because turtles could be detected even when they were fully submerged. Because of these high detection rates, we used only aerial data to develop predictive models of sea turtle distributions.
 

Distribution and Abundance

<p>The three maps above show predicted relative abundance of sea turtles by season, based on two years of digital video aerial survey data (2012-2014). Models used observation data from aerial surveys and remotely sensed environmental covariate data to predict abundance across the study area.</p>

<p>Hundreds of sea turtles were observed offshore of Maryland. Loggerhead and Leatherback Sea Turtles were the most frequently observed species, although all five species were seen in the study area. Sea turtles were most abundant from May to October, with very few present in the study area in winter. Models predicted highest turtle densities far from shore off Virginia in spring, in areas with warmer sea surface temperatures. In summer, sea turtles were predicted to be distributed across a broader range, as females move to shore to lay eggs. Sea turtles were most widely distributed across the study area in fall, predominantly in offshore areas. Sea turtle abundance and species diversity was highest in the Maryland study area during this season.</p>

The three maps above show predicted relative abundance of sea turtles by season, based on two years of digital video aerial survey data (2012-2014). Models used observation data from aerial surveys and remotely sensed environmental covariate data to predict abundance across the study area.

Hundreds of sea turtles were observed offshore of Maryland. Loggerhead and Leatherback Sea Turtles were the most frequently observed species, although all five species were seen in the study area. Sea turtles were most abundant from May to October, with very few present in the study area in winter. Models predicted highest turtle densities far from shore off Virginia in spring, in areas with warmer sea surface temperatures. In summer, sea turtles were predicted to be distributed across a broader range, as females move to shore to lay eggs. Sea turtles were most widely distributed across the study area in fall, predominantly in offshore areas. Sea turtle abundance and species diversity was highest in the Maryland study area during this season.

 

For More Information

For more information, see Chapters 1011, and 12 in the technical report.
 

References

  • Epperly SP, Braun J, Chester AJ, Cross FA, Merriner JV, Tester PA (1995) Winter distribution of sea turtles in the vicinity of Cape Hatteras and their interactions with the summer flounder trawl fishery. Bulletin of Marine Science 56:547–568
  • Gardner B, Sullivan PJ, Epperly S, Morreale SJ (2008) Hierarchical modeling of bycatch rates of sea turtles in the western North Atlantic. Endangered Species Research 5:279–289. doi: 10.3354/esr00105 
  • James MC, Ottensmeyer CA, Myers RA (2005) Identification of high-use habitat and threats to leatherback sea turtles in northern waters: New directions for conservation. Ecology Letters 8:195–201. doi:10.1111/j.1461-0248.2004.00710.x 
  • Hazel J, Lawler IR, Marsh H, Robson S (2007) Vessel speed increases collision risk for the green turtle Chelonia mydas. Endangered Species Research 3:105–113 
  • Murray KT, Orphanides CD (2013) Estimating the risk of loggerhead turtle Caretta caretta bycatch in the US mid-Atlantic using fishery-independent and -dependent data. Marine Ecology Progress Series 477:259–270. doi: 10.3354/meps10173 
  • Read A (2013) Chapter 9: Sea Turtles. In: South Atlantic Information Resources: Data Search and Literature Synthesis, OCS Study BOEM 2013-01157. US Department of the Interior, Bureau of Ocean Energy Management, New Orleans, LA. pp 603-613 
  • Wallace BP, DiMatteo AD, Bolten AB, Chaloupka MY, Hutchinson BJ, Abreu-Grobois FA, Mortimer JA, Seminoff JA, Amorocho D, Bjorndal KA, Bourjea J, Bowen BW, Briseño Dueñas R, Casale P, Choudhury BC, C osta A, Dutton PH, Fallabrino A, Finkbeiner EM, Girard A, Girondot M, Hamann M, Hurley BJ, López-Mendilaharsu M, Marcovaldi MA, Musick JA, Nel R, Pilcher NJ, Troëng S, Witherington B, Mast RB (2011) Global conservation priorities for Marine turtles. PLoS One 6: e24510. doi:10.1371/journal.pone.0024510
 
Photo Credits: Header image © Daniel Calatayud
Biodiversity Research Institute