144 



Fishery Bulletin 103(1) 



prey collected. Summing the total volume of each prey 

 item and dividing it by the total stomach volume for those 

 samples, where the prey item was present, yielded the 

 mean percent volume. Regression analysis was done to 

 determine if any correlation existed between sea surface 

 temperature, sample volume, and size of turtle. 



Results 



Loggerhead sea turtles collected in our study were found 

 widely distributed over the central North Pacific Ocean 

 and there was no apparent difference in distribution 



16 



14 



12 



10-19 cm 20-29 cm 30-39 cm 40-49 cm 50-59 cm 

 Curved carapace length (cm) 



60-69 cm 70-79 cm 



Figure 2 



Size distribution for the 52 loggerhead sea turtles [Caretta caretta) obtained 

 as samples in the high-seas driftnet fishery. Sizes were grouped into 

 10-cm size classes. 



21 



20.0 



19.0 



180 



17.0 



16.0 



15.0 



• • • I 



• •* * • 



• • * '• 



• • • y m ••• 



0.0 10.0 20.0 30.0 40.0 50 



Curved carapace length (cm) 



60.0 



700 



Figure 3 



Relationship between curved carapace length (CCL, cm) of loggerhead sea 

 turtles [Caretta caretta) and sea surface temperature iSST, n = 52). 



between size classes (Fig. 1). The turtle specimens 

 ranged from 13.5 cm to 74.0 cm curved carapace length 

 (CCL, Fig. 2); the mean was 44.8 [±14.5] cm CCL. Figure 

 2 shows the distribution of turtles in each 10-cm size 

 class. Sea surface temperatures in the area of cap- 

 ture ranged from 16° to 20°C. There was no correlation 

 between size of turtle and sea surface temperature in 

 the area of capture (F=0.58, r 2 =0.01, Fig. 3). 



All 52 stomachs examined contained prey items; the 

 level of fill varied from 6 mL to 1262 mL. Items found 

 in the anterior portion of the stomach were the most 

 identifiable and contents varied between turtles. Un- 

 identifiable remains were located mainly in the poste- 

 rior end of the stomach or the intes- 

 tines if a whole gastrointestinal tract 

 was analyzed. Only one of the samples 

 analyzed included an entire gastroin- 

 testinal tract. 



A taxonomic listing of diet items 

 identified for the loggerhead sea turtles 

 of the central North Pacific is shown in 

 Table 1 along with frequency of occur- 

 rence and mean percent sample volume 

 of each prey item. The six most com- 

 mon (frequent) prey items were iden- 

 tified. These included Janthina spp., 

 which occurred in 75% of samples, and 

 Planes spp., which occurred in 56% of 

 samples. Lepas spp. occurred in 52% 

 of the samples, and Carinaria cithara 

 was found in 50% of samples. Velella 

 velella, was found in 25% of the sam- 

 ples, and pyrosomas were found in 21% 

 of samples (Table 1). Other common 

 food items found in stomachs were fish 

 eggs (25% of stomachs), salps, amphi- 

 pods (46% of stomachs), small fish, and 

 plastic items (35% of stomachs. Table 

 1). Some plastic items included small 

 plastic beads, thin plastic sheets, poly- 

 propylene line, and even a small plastic 

 fish, which had been an individual soy 

 sauce container. Although Velella, py- 

 rosomas, and salps were represented 

 as prey items in our samples, other 

 types of jellies may not have been well 

 represented because their soft bodies 

 may dissolve more quickly in stomach 

 acids. It is also possible that unidenti- 

 fied jellies may comprise the unidenti- 

 fied remains, which occurred in 71% 

 of stomachs and comprised 13.8% of 

 total sample volume; however, a por- 

 tion of the unidentified remains were 

 likely masticated portions of identified 

 prey items. Table 2 shows the mean 

 percent prey item volumes for the six 

 most common prey items. The six most 

 common prey items can be ranked from 

 largest to smallest mean volumes in 



80.0 



