title: Age and residency duration of loggerhead turtles at a North Pacific bycatch hotspot using skeletochronology.
abstract: For migratory marine animals, like sea turtles, effective conservation can be challenging because key demographic information such as duration of life stages and exposure to spatially explicit threats in different habitats are often unknown. In the eastern Pacific near the Baja California Peninsula (BCP), Mexico, tens of thousands of endangered North Pacific loggerhead sea turtles (Caretta caretta) concentrate at a foraging area known to have high rates of fishery bycatch. Because stage survivorship of loggerheads in the BCP will vary significantly depending on the number of years spent in this region, we applied skeletochronology to empirically estimate residency duration in this loggerhead hotspot. The observed age distribution obtained from skeletochronology analysis of 146 dead-stranded loggerheads ranged from three to 24 years old, suggesting a BCP residency of >20 years. Given the maximum estimated age and a one-year migration to western Pacific nesting beaches, we infer age-at-maturation for BCP loggerheads at ~25 years old. We also examine survivorship at varying BCP residency durations by applying our findings to current annual mortality estimates. Predicted survivorship of loggerheads spending over 20 years in this BCP foraging habitat is less than 10%, and given that ~43,000 loggerhead turtles forage here, a significant number of turtles are at extreme risk in this region. This is the first empirical evidence supporting estimated age-at-maturation for BCP North Pacific loggerheads, and the first estimates of BCP stage survivorship. Our findings emphasize the urgent need for continued and effective international conservation efforts to minimize bycatch of this endangered species.
authors.affiliation: Division of Biological Sciences, Ecology, Behavior, and Evolution Section, University of California, San Diego, La Jolla, CA 92093-0116, USA ; Southwest Fisheries Science Center, NOAA-National Marine Fisheries Service, La Jolla, California 92037, USA.
authors.forename: Calandra N Turner
authors.initials: CN
authors.lastname: Tomaszewicz
authors.affiliation: Southwest Fisheries Science Center, NOAA-National Marine Fisheries Service, La Jolla, California 92037, USA.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Seminoff
authors.affiliation: Southeast Fisheries Science Center, NOAA, National Marine Fisheries Service, Beaufort, North Carolina 28516, USA.
authors.forename: Larisa
authors.initials: L
authors.lastname: Avens
authors.affiliation: Southeast Fisheries Science Center, NOAA, National Marine Fisheries Service, Beaufort, North Carolina 28516, USA.
authors.forename: Lisa R
authors.initials: LR
authors.lastname: Goshe
authors.affiliation: Center for Ocean Solutions, Stanford University, Pacific Grove, California 93940, USA.
authors.forename: S Hoyt
authors.initials: SH
authors.lastname: Peckham
authors.affiliation: Marine Biology Department, Universidad Autonoma de Baja California Sur., La Paz, Baja California Sur, Mexico.
authors.forename: Juan M
authors.initials: JM
authors.lastname: Rguez-Baron
authors.affiliation: School of Biology and Ecology, University of Maine, Orono, Maine 04469, USA.
authors.forename: Kalyn
authors.initials: K
authors.lastname: Bickerman
authors.affiliation: Division of Biological Sciences, Ecology, Behavior, and Evolution Section, University of California, San Diego, La Jolla, CA 92093-0116, USA.
authors.forename: Carolyn M
authors.initials: CM
authors.lastname: Kurle
keywords: Endangered species; age-at-maturation; demography; sea turtle; sink habitat; survivorship
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