Normalizing home ranges of immature Kemp’s ridley turtles (Lepidochelys kempii) in an important estuarine foraging area to better assess their spatial distribution

ABSTRACT

Kemp’s ridley turtles (Lepidochelys kempii) are critically endangered sea turtles that forage seasonally in Chesapeake Bay, a large estuary on the east coast of the United States. Most of the Kemp’s ridley turtles foraging in the bay are immature. When tracking these animals, satellite transmitter retention times have been low compared with adult marine turtles of other species. The immature Kemp’s ridleys’ small size and rapid growth leads to shorter, more variable deployments, limiting the use of data. These limited data leave critical questions remaining about the animals’ habitat usage that are difficult to answer without substantially more deployments. A novel sensitivity analysis using simulated deployments indicated that too few animals were tagged with satellite transmitters to identify all possible home-range areas in the Bay. We used simulation to create animal deployments of equal duration to address biases (differing lengths of deployments and time between locations) in home-range analyses and boost the information available from relatively short deployments. Combined home ranges from simulated deployments identified important areas for these animals in the south-western portions of the Chesapeake Bay and in the nearshore areas of the Bay north to the middle of the Bay. These areas represent opportunities for managers to mitigate impacts from boating, dredging, military activities and fishing, and could inform critical habitat designations under the United States Endangered Species Act. Habitat modelling may be needed to identify additional important areas in the Bay where animals were not observed via satellite tracking.

KEYWORDS:

• Satellite telemetry
• simulation
• marine turtle
• sensitivity analysis
• Chesapeake Bay

Acknowledgements

The authors wish to acknowledge the staff and volunteers of Virginia Aquarium & Marine Science Center for supporting deploying transmitters and rehabilitation efforts; Joel Bell and the Marine Resources division of Naval Facilities Engineering Command for project management and field support; Dan Engelhaupt and Jessica Aschettino of HDR Inc. for project management; Laura Sparks and Naval Undersea Warfare Center for time support, and Len Thomas for technical advice.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of the current study are available from the Naval Facilities Engineering Command upon reasonable request. Contact Joel Bell or the Marine Resource Specialist Group for permission. They can be viewed on Ocean Biogeographic Information System Spatial Ecological Analysis of Megavertebrate Populations (OBIS-SEAMAP) at http://seamap.env.duke.edu/dataset/1018.

Additional information

Funding

Funding was provided by the United States Navy (United States Fleet Forces Command) under Contract Number N62470-15-D-8006, Task Order N624701731/XO59. The funding organization was allowed to review the manuscript prior to submission but did not influence its contents, analyses, or findings.