Three Decades of Stranding Data Reveal Insights Into Endangered Hawksbill Sea Turtles in Hawaiʻi

Hawksbill sea turtles Eretmochelys imbricata inhabiting the Hawaiian Islands are extremely rare and listed as Endangered under the U.S. Endangered Species Act. 

The scarcity of data on basic hawksbill ecology continues to hinder effective management of the species. We analyzed stranding data collected between 1984 and 2018 to gain insights into the distribution, demography, and conservation challenges facing hawksbills in Hawaiʻi. 

In doing so, we present a comprehensive description of the population across developmental stages and rank threats that may be impeding their successful recovery. 

Over the >30 year dataset, we recorded a total of only 111 juvenile and adult life stage hawksbill stranding events. Interactions with nearshore recreational fishing gear were documented for a large proportion (48.6%) of stranding events in the Hawaiian Islands, identifying this as the primary management challenge for the species. Stranding events were biased towards females (female to male sex ratio of 4.8:1), which may be indicative of the population as a whole. 

Even though the majority of hawksbill nesting is on the islands of Hawaiʻi and Maui, the greatest number of juvenile to adult strandings was found to be on the island of Oahu (N = 47). Temporal distribution of the majority of adult hawksbill strandings (72.2%) occurred during a four-month period between June and September.

 We discuss these and other findings that help identify future research and conservation efforts to mitigate anthropogenic threats in Hawaiʻi for this enigmatic population.

Brunson S, Gaos AR, Kelly IK, Van Houtan KS, Swimmer Y, Hargrove S, Balazs GH, Work TM, Jones TT (2021). Three decades of stranding data reveal insights into endangered hawksbill sea turtles in Hawaiʻi. Endangered Species Research, in press. https://doi.org/10.3354/esr01167