Parker et al .: Diet of Caretto caretta in the central North Pacific 



149 



Converting CCL to straight carapace length (SCL; 

 using the conversion equation: CCL=1.388+(1.053) SCL, 

 in Bjorndal et al., 2000), size classes found in our study 

 ranged from 11.5 cm to 68.9 cm SCL with a mean of 

 41.2 [±12.4] cm SCL. The East Pacific recruits were 

 slightly larger with means of 46.9-61.9 cm SCL (Semi- 

 noff et al., 2004). Most of these turtles were immature 

 to subadult turtles, and only a few were adult-size tur- 

 tles. According to Zug et al. (1995), the loggerhead sea 

 turtles recruiting to the nearshore and neritic habitats 

 of Baja California are likely 10 years of age or older, 

 indicating that these turtles might spend as many as 

 10 years before arriving at their East Pacific foraging 

 habitat. After returning to the West Pacific, satellite 

 telemetry has found that adult loggerhead sea turtles 

 also reside in both neritic and pelagic habitats (Baba 

 et al., 1992, 1993; Kamezaki et al., 1997; Sakamoto 

 et al., 1997) putting them at risk of interaction with 

 nearshore gillnet fisheries as well as pelagic longline 

 fisheries. Hitase et al. (2002) found a size difference 

 between adults in neritic and oceanic habitats — the 

 postnesting females that chose oceanic habitats were 

 smaller (mainly <80.0 cm) than those that used neritic 

 habitats for postnesting foraging — and also suggested 

 that some adult turtles may not recruit to neritic areas 

 near Japan and China. This may be evidence that some 

 loggerhead sea turtles remain in the oceanic habitat 

 their whole life cycle, returning nearshore only to mate 

 or nest. In the Atlantic, juveniles as well as adults of 

 this species can be found in neritic foraging habitats of 

 the Gulf of Mexico, and these turtles can have interac- 

 tions with coastal trawl and other coastal fisheries in 

 the area (Plotkin et al., 1993). Juvenile turtles have 

 also been observed and captured in areas along the 

 eastern coast of the United States where they have 

 been found feeding on benthic invertebrates (Burke et 

 al., 1990; Epperly et al., 1990). Very small, neonate 

 loggerhead sea turtles have been found associating 

 with and foraging in Sargassum drifts while they are 

 transported by the Gulf Stream into the mid-Atlantic 

 (Witherington, 2002); therefore, the harvest of Sargas- 

 sum or trawling through this area would affect these 

 juveniles. There is some evidence that juvenile Atlantic 

 loggerhead sea turtles may move between coastal and 

 pelagic forage habitats, which would expose them to 

 both coastal and pelagic fisheries (Witzell, 2002). In 

 the Mediterranean, both juvenile and adult loggerhead 

 sea turtles also have variety of foraging behaviors. In 

 the eastern Mediterranean, postpelagic juveniles and 

 adults forage mainly in neritic habitats on benthic prey 

 items where they would interact with coastal trawl and 

 other artesianal fisheries (Godley et al., 1997). In the 

 western Mediterranean, juvenile turtles of this species 

 forage in both pelagic as well as neritic habitats, where 

 they are at risk of fishery interactions in many differ- 

 ent fisheries including longline, trawling, and coastal 

 fisheries (Tomas et al., 2001). Postpelagic juveniles in 

 the Mediterranean may be recruits from the Atlantic 

 Ocean or may come from the endemic Mediterranean 

 population. Adult loggerhead sea turtles have been 



noted to also move between the eastern and western 

 basins of the Mediterranean in response to seasonal 

 temperature changes (Bentivegna, 2002). During this 

 migration between two benthic feeding areas, some 

 of the turtles would spend extensive amounts of time 

 in the pelagic habitat likely foraging on pelagic prey 

 items. This intra-Mediterranean movement puts these 

 turtles at risk of interactions with a multinational 

 fishery contingent of pelagic as well as coastal fisheries 

 (Bentivegna, 2002). 



One possible way to mitigate increased fisheries in- 

 teractions in the Pacific and other areas might be to 

 identify specific loggerhead foraging areas for protec- 

 tion, such as the area around Baja California, Mexico. 

 In the central North Pacific, our study (Fig. 1), as well 

 as recent satellite tracking studies of juvenile and adult 

 loggerhead sea turtles (Hitase et al., 2002; Parker et 

 al., 2003; Polovina et al., 2004), has indicated that 

 the area west of and around the Emperor seamounts, 

 between 160° and 180°E might also be an important 

 foraging habitat. Most of the turtles in our study were 

 collected from this area (Fig. 1) and one juvenile spent 

 10 months west of the Emperor Seamounts, between 

 160° and 170°E, before its satellite transmitter stopped 

 transmitting data (Parker et al., 2003). In this area, 

 the southern edge of the Kuroshiro Extension Current 

 forms numerous eddies that are semipermanent fea- 

 tures throughout the year. Reduction of fishing effort 

 or other fishery mitigation techniques in this area may 

 greatly decrease the number of fisheries interactions 

 that Pacific loggerhead sea turtles experience. Interna- 

 tional cooperation is needed in order to manage these 

 foraging habitats. More studies also need to be done 

 on the ecology of these turtles so that fishery interac- 

 tions at all life stages can be addressed and so that a 

 total picture of the life history of this species can be 

 obtained. 



Acknowledgments 



We would like to acknowledge the hard work of all the 

 NMFS fishery observers for obtaining the samples, Russ 

 Miya and Bryan Winton for their help in the initial 

 sorting, and Mike Seki and Kevin Landgraf for their 

 help in identifying prey items. We would also like to 

 acknowledge the review and comments of Alan Bolten, 

 Jeffrey Seminoff, George Antonelis, Jerry Wetherall, 

 Colin Limpus, Judith Kendig, Francine Fiust, Shawn 

 Murakawa, and two anonymous reviewers. 



Literature cited 



Allen, W. 



1992. Loggerhead dies after ingesting marine debris. 

 Mar. Turtle Newsl. 58:10. 

 Andersen, V., and J. Sardou. 



1994. Pyrosoma atlanticum (Tunicata, Thaliacea): diel 

 migration and vertical distribution as a function of 

 colony size. J. Plankton Res. 16(4):337-349. 



