The developmental biogeography of hawksbill sea turtles in the North Pacific.
High seas oceanic ecosystems are considered important habitat for juvenile sea turtles, yet much remains cryptic about this important life-history period. Recent progress on climate and fishery impacts in these so-called lost years is promising, but the developmental biogeography of hawksbill sea turtles (Eretmochelys imbricata) has not been widely described in the Pacific Ocean. This knowledge gap limits the effectiveness of conservation management for this globally endangered species. We address this with 30 years of stranding observations, 20 years of bycatch records, and recent simulations of natal dispersal trajectories in the Hawaiian Archipelago. We synthesize the analyses of these data in the context of direct empirical observations, anecdotal sightings, and historical commercial harvests from the insular Pacific. We find hawksbills 0-4 years of age, measuring 8-34 cm straight carapace length, are found predominantly in the coastal pelagic waters of Hawaii. Unlike other species, we find no direct evidence of a prolonged presence in oceanic habitats, yet satellite tracks of passive drifters (simulating natal dispersal) and our small sample sizes suggest that an oceanic phase for hawksbills cannot be dismissed. Importantly, despite over 600 million hooks deployed and nearly 6000 turtle interactions, longline fisheries have never recorded a single hawksbill take. We address whether the patterns we observe are due to population size and gear selectivity. Although most sea turtle species demonstrate clear patterns of oceanic development, hawksbills in the North Pacific may by contrast occupy a variety of ecosystems including coastal pelagic waters and shallow reefs in remote atolls. This focuses attention on hazards in these ecosystems - entanglement and ingestion of marine debris - and perhaps away from longline bycatch and decadal climate regimes that affect sea turtle development in oceanic regions.
NOAA Fisheries Pacific Islands Fisheries Science Center Honolulu Hawaii 96818; Nicholas School of the Environment Duke University Durham North Carolina 27708; Present address: Monterey Bay Aquarium Monterey California 93940.
Kyle S
KS
Van Houtan
Joint Institute for Marine and Atmospheric Research University of Hawaii Honolulu Hawaii 96822.
Devon L
DL
Francke
Joint Institute for Marine and Atmospheric Research University of Hawaii Honolulu Hawaii 96822.
Sarah
S
Alessi
NOAA Fisheries Pacific Islands Fisheries Science Center Honolulu Hawaii 96818.
T Todd
TT
Jones
National Research Council National Academy of Sciences Washington District of Columbia 20001.
Summer L
SL
Martin
Pacific Cooperative Studies Unit University of Hawaii Honolulu Hawaii 96822; World Turtle Trust Kailua Hawaii 96734.
Lauren
L
Kurpita
Hawaii Wildlife Fund Paia Hawaii 96779.
Cheryl S
CS
King
Cascadia Research Collective Olympia Washington 98501.
Robin W
RW
Baird
Bycatch; coastal ecology; natal dispersal; ocean plastics; pollution; spatial structure