After about 15 davs they hatch, still living off the yolk sac (Figure 5). After 

 absorption of the yolk the postlarvae must depend upon the external environment for 

 their food (Figure 6). 



Figure 5. Newly-hatched halibut larva showing yolk sac. Size: 1 cm. (3/8 inch). 





d 



m 



Figure 6. Halibut postlarva, yolk has been absorbed. Size: 1.7 cm. (11/16 inch). 



Like the eggs and larvae, the postlarvae are free floating and may be transported 

 many hundreds of miles by the ocean currents, which in the eastern North Pacific 

 tend to move counterclockwise in the Gulf of Alaska and westward along the 

 Alaskan Peninsula and Aleutian Islands (Figure 7). The velocity of some parts of this 

 westward-moving subarctic current and Alaska Stream mav reach as high as 10 knots, 

 particularlv at the edge of the continental shelf. Thus the floating eggs, the developing 

 larvae and the postlarvae mav be dispersed far from the point where they were 

 produced. Eggs produced on the shelf edge in the eastern Gulf of Alaska and even 

 from more distant grounds to the south could, under some conditions, be the source 

 of the young found in Bering Sea. 



140° 



150° l€0° 



r70°E 180° 



I70°W 160° 



150° 



140° 



130° 



BO» 



Figure 7. Map of North Pacific, showing main ocean currents. (from Dodimead et al, 1NPFC Bull. 13) 



