Marine Resources Assessment for the Marianas Operating ... - SPREP

AUGUST 2005 FINAL REPORT
Leatherback turtles predominantly feed upon gelatinous zooplankton such as cnidarians (jellyfish and
siphonophores) and tunicates (salps and pyrosomas); however, a wide variety of other prey items are
known (Bjorndal 1997; NMFS and USFWS 1998c). In offshore waters of the North Pacific Ocean,
leatherbacks appear to feed primarily on pyrosomas, although they have also been known to ingest
longline hooks baited with sama (tuna bait) and squid (swordfish bait) (Davenport and Balazs 1991;
Skillman and Balazs 1992; Grant 1994; Work and Balazs 2002). Leatherbacks feed throughout the
water column from the surface to depths of 1,200 m (Eisenberg and Frazier 1983; Davenport 1988).
Studies of leatherback turtle diving patterns off St. Croix, USVI suggested that they forage at night on
the deep-scattering layer (DSL), a strata of vertically migrating zooplankton that concentrates below
600 m during the day and moves to the surface at night (S. Eckert et al. 1989). Siphonophores, salps,
and jellyfish are primary constituents of the DSL.
Mating is thought to occur prior to or during the migration from temperate to tropical waters (Eckert
and Eckert 1988). Typical clutches range in size from 50 to over 150 eggs, with clutch sizes in the
western Pacific being generally larger than in the eastern Pacific. The incubation period lasts from 55
to 75 days. Females nesting on the Pacific coast of Mexico lay 1 to 11 clutches in a single season at
9- to 10-day intervals (NMFS and USFWS 1998c). Females remain in the general vicinity of the
nesting habitat during inter-nesting intervals, with total residence in the nesting/inter-nesting habitats
lasting up to four months (K. Eckert et al. 1989; Keinath and Musick 1993). Most adult females return
to nest on their natal beach every two to three years; however, remigration intervals (the number of
years between successive nesting seasons) between one and five years have been recorded (Boulon
et al. 1996). In the Mexican Pacific, the nesting season of the leatherback extends from November to
February, with some females arriving as early as August (Fritts et al. 1982; NMFS and USFWS
1998c). In the western Pacific, nesting peaks in May and June in China, June and July in Malaysia,
and December and January in Queensland, Australia (NMFS and USFWS 1998c).
The leatherback is the deepest diving sea turtle. The depth to which a leatherback dives is influenced
by the age of the turtle, the reason for the dive, and the proximity to shore. In general, older
leatherbacks and those found in the open ocean make deeper dives than younger individuals and
those that inhabit shallower waters (Ernst et al. 1994; Salmon et al. 2004). Leatherbacks in open
ocean environments frequently exhibit V-shaped dive patterns (in which they descend to a certain
depth and then immediately ascend to the surface), whereas leatherbacks in shallow water
environments more often exhibit U-shaped dive patterns (in which they swim down to the ocean floor,
remain on the bottom for several minutes, and then return directly to the surface) (Eckert et al. 1996).
Average dive depths for post-nesting leatherbacks off the continental shelf of St. Croix ranged from
35 to 122 m, with estimated maximum depths of over 1,000 m (S. Eckert et al. 1989; Eckert et al.
1996). Typical dive durations averaged 6.9 to 14.5 min per dive, with a maximum of 42 min (Eckert et
al. 1996). On average, day dives tend to be deeper, longer, and less frequent than those at night (S.
Eckert et al. 1989).
3.2.1 Literature Cited
Abraham, T., M. Beger, D. Burdick, E. Cochrane, P. Craig, G. Didonato, D. Fenner, A. Green, Y. Golbuu,
J. Gutierrez, M. Hasurmai, C. Hawkins, P. Houk, D. Idip, D. Jacobson, E. Jospeh, T. Keju, J.
Kuartei, S. Palik, L. Penland, S. Pinca, K. Rikim, J. Starmer, M. Trianni, S. Victor, and L.
Whaylen. 2004. Status of the coral reefs in Micronesia and American Samoa. Edited by R. Kelty,
and J. Kuartei. Pages 381-409 in C. Wilkinson, ed. Status of Coral Reefs of the World: 2004.
Townsville, Queensland: Australian Institute of Marine Science.
Anonymous. 1976. She 'held breath' to elude capture. Press Release: Pacific Daily News. 22 November,
p. 4.
Arenas, P., and M. Hall. 1992. The association of sea turtles and other pelagic fauna with floating objects
in the eastern tropical Pacific Ocean. Pages 7-10 in M. Salmon and J. Wyneken, eds.
Proceedings of the Eleventh Annual Workshop on Sea Turtle Biology and Conservation. NOAA
Technical Memorandum NMFS-SEFSC-302.
Balazs, G.H. 1976. Green turtle migrations in the Hawaiian archipelago. Biological Conservation 9:125-
140.
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