408 



Fishery Bulletin 104(3) 



8-10 mm SL 





 2 



4 

 6 

 8 

 10 

 12 

 14 

 16 



1 2 3 4 5 6 7 8 9 10 1 1 12 13 14 15 16 17 18 19 20 21 



10-12 mm SL 



1 2 3 4 5 6 7 8 9 10 1 1 12 13 14 15 16 17 18 19 20 



12-14 mm SL 



1 2 3 4 5 6 7 8 9 10 1 1 12 13 14 15 16 17 18 19 20 



1 2 3 4 5 6 7 8 9 10 1 1 12 13 14 15 16 17 18 19 20 21 

 Time (30-sec intervals) 



Figure 5 



In silu vertical distribution trajectories for giant trevally (Caranx 

 ignobilis) larvae and juveniles of four size groups. Locations of 

 observations were  Wan Li Tong, 14 May 2004;  Her Chen, 

 14 May 2004; ▲ Nan Wan Bay North, 24 May 2004; A Nan 

 Wan Bay South, 24 May 2004. (A) 8-10 mm SL larvae; (B) 

 10-12 mm SL larvae; (C)12-14 mm SL larvae; ID) 14-18 mm 

 SL larvae. 



2 3 4 5^ 90 



Figure 6 



Frequency distribution of in situ swimming 

 directions based on bearings taken every 30 

 seconds for an 18-mm-SL giant trevally (Caranx 

 Ignobilis,) at Nan Wan Bay South. Bearings are 

 grouped into 10" intervals. The radius that pen- 

 etrates the outer circle (thin line) is the mean 

 direction. This significantly directional distribu- 

 tion (Rayleigh test, P=0.000001) has an r (length 

 of the mean vector) of 0.76, which is close to the 

 overall mean for the 16 directional individuals 

 (Table 3). The numbers on dashed lines represent 

 the number of times that bearing was recorded 

 for a larva. 



Other behaviors 



Unplanned observations were made of feeding, 

 interactions with other pelagic animals, and 

 reactions with the bottom. At least nine of the 

 24 larvae were seen feeding, grabbing at, and 

 apparently eating small zooplankton while swim- 

 ming. One 12-mm larva encountered a large (ca. 

 30-40 cm) Naso sp. in open water and changed 

 direction by 140° over the following minute. An 

 11-mm C. ignobilis encountered a jellyfish and 

 briefly (<30 s) hovered under it. Five individuals 

 (9-13.5 mm SL) came into visual contact with 

 relatively high-relief coral reefs (at least the 

 divers could clearly see the reefs) at Wan Li Tong 

 and Her Chen. The larvae showed no particu- 

 lar interest in the reefs; two ascended slightly 

 (0.5-1 m), two maintained a distance of 3-4 m 

 from the reef surface as they swam over it, and 

 one turned offshore. One 12.5-mm larva passed 

 through a strong thermocline at 8 m that was 

 very noticeable to the divers without slowing 

 or giving any indication that the temperature 

 change was sensed. 



