The Great Migration: From Laniakea to French Frigate Shoals
Every year, many Hawaiian green sea turtles (locally known as honu) undertake a remarkable 1,200-mile (1,931-kilometer) round-trip migration. They travel from their foraging grounds in the main Hawaiian Islands to reproduce and nest at French Frigate Shoals (FFS) in the Northwestern Hawaiian Islands, before swimming all the way back again.
For example, a turtle traveling from Laniakea Beach on Oahu’s North Shore to FFS covers a distance of about 902 km (560 miles) one way.
Since 1973, biologists from the PIFSC’s Marine Turtle Biology and Assessment Program have shadowed this annual journey to the remote atolls of FFS to monitor nesting activity and ensure the population’s health.
[NOAA, 2021]
Resilience in a Changing Environment
The nesting season typically begins between mid-March and mid-May. While Laniakea’s honu have historically preferred East Island within the French Frigate Shoals, Hurricane Walaka virtually destroyed that specific island in October 2018. Honu are resilient creatures, and while they are adapting to this loss, researchers are still observing where these displaced individuals will choose to establish their future nests.
[Malama na Honu, 2021]
What’s on the Menu for a Honu?
Green sea turtles are primarily herbivores. Their diet consists mostly of seagrasses and algae, known in Hawaii as limu, which grows on coral reefs and shallow rocks. Interestingly, limu is also a staple in Hawaiian cuisine, often enjoyed as a healthy vegetable in dishes like poke, salads, and stews.
Exploring French Frigate Shoals: A Marine Sanctuary
Located about 487 nautical miles northwest of Honolulu, French Frigate Shoals is an open atoll featuring a large, crescent-shaped reef surrounding small, sandy islets. Although the land area is tiny (about 67 acres), the surrounding coral reef spans over 232,000 acres—a massive underwater metropolis.
This area boasts one of the most significant reef systems in the Northwestern Hawaiian Islands, supporting a vast array of life:
- Coral Variety: Home to acropora table coral, finger coral, and stony coral.
- Invertebrates: Over 600 species, including endemic sponges, snails, and lobsters found nowhere else on Earth.
- Marine Plants: More than 150 species of algae (red, green, and brown).
- Predators & Schools: The outer waters support gray reef sharks, butterfly fish, and large schools of jacks.
[U.S. Fish & Wildlife Service, 2021]
A Refuge for Mega-Fauna
French Frigate Shoals is a vital nursery for Hawaii’s “charismatic megafauna.” Over 90% of the Hawaiian green turtle population travels here for safe nesting. Satellite tagging has shown that while most return to the main Hawaiian Islands to feed, some travel as far as Johnston Atoll. Additionally, the islets serve as a primary refuge for the endangered Hawaiian monk seal, making it a critical stronghold for Pacific marine conservation.
[U.S. Fish & Wildlife Service, 2021]
References
References
Ellis, G. H. (2021, October 21). Satellite telemetry of migrant male and female green turtles breeding in the Hawaiian Islands. Turtles.org. http://www.turtles.org/ffs/migrate/ffsmigrt.htm
Malama na Honu. (2021, October 24). Turtles in the Hawaiian Islands. https://malamanahonu.org/information/
NOAA. (2021, October 24). By the numbers: The annual migration of green sea turtles in Hawaiʻi. National Oceanic and Atmospheric Administration. https://www.fisheries.noaa.gov/feature-story/numbers-annual-migration-green-sea-turtles-hawaii
U.S. Fish & Wildlife Service. (2021, October 21). French Frigate Shoals. https://www.fws.gov/refuge/Hawaiian_Islands/about/French_Frigate_Shoals.html
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