Limits...
The developmental biogeography of hawksbill sea turtles in the North Pacific.

Van Houtan KS, Francke DL, Alessi S, Jones TT, Martin SL, Kurpita L, King CS, Baird RW - Ecol Evol (2016)

Bottom Line: This knowledge gap limits the effectiveness of conservation management for this globally endangered species.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.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.

View Article: PubMed Central - PubMed

Affiliation: NOAA FisheriesPacific Islands Fisheries Science CenterHonoluluHawaii96818; Nicholas School of the EnvironmentDuke UniversityDurhamNorth Carolina27708; Present address: Monterey Bay AquariumMontereyCalifornia93940.

ABSTRACT
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.

No MeSH data available.


Despite considerable sea turtle bycatch and extensive observer monitoring, the Hawaii‐based longline fleet has recorded zero hawksbill interactions. (A) Observer data from 1994 to 2014 from the tuna‐targeting deep‐set fleet and the swordfish‐targeting shallow‐set fleet suggest roughly 5697 sea turtle interactions. Fishery regulations from 2001 to present have resulted in significantly lower turtle bycatch. Locations and demographics of (B) loggerhead, (C) olive ridley, (D) leatherback, and (E) green turtles caught in fisheries. Light (shallow‐set) and dark (deep‐set) plotted lines are the 95% kernel density estimates of each fishery's extent. Filled circles are bycatch locations from both fisheries, and circle size indicates turtle length corresponding to legend on right panels. Columns in length frequency plots however are colored (as noted above) by fishery. Both fisheries interact with a range of demographics, from young juveniles to breeding adults, from all four species.
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ece32034-fig-0004: Despite considerable sea turtle bycatch and extensive observer monitoring, the Hawaii‐based longline fleet has recorded zero hawksbill interactions. (A) Observer data from 1994 to 2014 from the tuna‐targeting deep‐set fleet and the swordfish‐targeting shallow‐set fleet suggest roughly 5697 sea turtle interactions. Fishery regulations from 2001 to present have resulted in significantly lower turtle bycatch. Locations and demographics of (B) loggerhead, (C) olive ridley, (D) leatherback, and (E) green turtles caught in fisheries. Light (shallow‐set) and dark (deep‐set) plotted lines are the 95% kernel density estimates of each fishery's extent. Filled circles are bycatch locations from both fisheries, and circle size indicates turtle length corresponding to legend on right panels. Columns in length frequency plots however are colored (as noted above) by fishery. Both fisheries interact with a range of demographics, from young juveniles to breeding adults, from all four species.

Mentions: Despite considerable fishing effort, Hawaii‐based fisheries have zero documented hawksbill interactions. From 1994 to 2014, the Hawaii‐based longline fisheries put forth a total effort of 329,304 sets containing 638,062,666 hooks. This effort was distributed in 279,930 sets containing 595,706,828 hooks in the deep‐set fleet, and 49,374 sets with 42,355,838 hooks in the shallow‐set fleet. Over this span, we estimate 5697 sea turtles were taken as bycatch, consisting of 2901 loggerheads, 1411 olive ridleys, 1027 leatherbacks, and 358 green turtles. Figure 4a plots the times series of sea turtle bycatch in these fleets, showing the considerable drop in bycatch after fishery management reforms in 2000 (Loggerhead MSRA Technical Advisory Team 2015). From 1994 to 2000, total sea turtle takes averaged 694 year−1, but this number was 61 year−1 over 2001–2014, a decline of 91.3% in both fleets.


The developmental biogeography of hawksbill sea turtles in the North Pacific.

Van Houtan KS, Francke DL, Alessi S, Jones TT, Martin SL, Kurpita L, King CS, Baird RW - Ecol Evol (2016)

Despite considerable sea turtle bycatch and extensive observer monitoring, the Hawaii‐based longline fleet has recorded zero hawksbill interactions. (A) Observer data from 1994 to 2014 from the tuna‐targeting deep‐set fleet and the swordfish‐targeting shallow‐set fleet suggest roughly 5697 sea turtle interactions. Fishery regulations from 2001 to present have resulted in significantly lower turtle bycatch. Locations and demographics of (B) loggerhead, (C) olive ridley, (D) leatherback, and (E) green turtles caught in fisheries. Light (shallow‐set) and dark (deep‐set) plotted lines are the 95% kernel density estimates of each fishery's extent. Filled circles are bycatch locations from both fisheries, and circle size indicates turtle length corresponding to legend on right panels. Columns in length frequency plots however are colored (as noted above) by fishery. Both fisheries interact with a range of demographics, from young juveniles to breeding adults, from all four species.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834323&req=5

ece32034-fig-0004: Despite considerable sea turtle bycatch and extensive observer monitoring, the Hawaii‐based longline fleet has recorded zero hawksbill interactions. (A) Observer data from 1994 to 2014 from the tuna‐targeting deep‐set fleet and the swordfish‐targeting shallow‐set fleet suggest roughly 5697 sea turtle interactions. Fishery regulations from 2001 to present have resulted in significantly lower turtle bycatch. Locations and demographics of (B) loggerhead, (C) olive ridley, (D) leatherback, and (E) green turtles caught in fisheries. Light (shallow‐set) and dark (deep‐set) plotted lines are the 95% kernel density estimates of each fishery's extent. Filled circles are bycatch locations from both fisheries, and circle size indicates turtle length corresponding to legend on right panels. Columns in length frequency plots however are colored (as noted above) by fishery. Both fisheries interact with a range of demographics, from young juveniles to breeding adults, from all four species.
Mentions: Despite considerable fishing effort, Hawaii‐based fisheries have zero documented hawksbill interactions. From 1994 to 2014, the Hawaii‐based longline fisheries put forth a total effort of 329,304 sets containing 638,062,666 hooks. This effort was distributed in 279,930 sets containing 595,706,828 hooks in the deep‐set fleet, and 49,374 sets with 42,355,838 hooks in the shallow‐set fleet. Over this span, we estimate 5697 sea turtles were taken as bycatch, consisting of 2901 loggerheads, 1411 olive ridleys, 1027 leatherbacks, and 358 green turtles. Figure 4a plots the times series of sea turtle bycatch in these fleets, showing the considerable drop in bycatch after fishery management reforms in 2000 (Loggerhead MSRA Technical Advisory Team 2015). From 1994 to 2000, total sea turtle takes averaged 694 year−1, but this number was 61 year−1 over 2001–2014, a decline of 91.3% in both fleets.

Bottom Line: This knowledge gap limits the effectiveness of conservation management for this globally endangered species.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.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.

View Article: PubMed Central - PubMed

Affiliation: NOAA FisheriesPacific Islands Fisheries Science CenterHonoluluHawaii96818; Nicholas School of the EnvironmentDuke UniversityDurhamNorth Carolina27708; Present address: Monterey Bay AquariumMontereyCalifornia93940.

ABSTRACT
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.

No MeSH data available.