FISHERY BULLETIN; VOL. 72, NO. 4 



Figure 5. Developmental stages of Sebastolobus alascanus. Above, 10.3-mm larva from mid-water trawl. Below, 16.0-mm 



transforming specimen from mid- water trawl. 



This increases to an average 36% in 6.0- to 

 10.0-mm larvae. Later stages of S. altiuelis 

 average 28% . Sebastolobus alascanus in the 10.0- 

 to 20.0-mm range average 31% , but this is reduced 

 to 27% in the remaining stages. 



Fin Development 



The pectoral fins of Sebastolobus are undif- 

 ferentiated buds in newly hatched larvae, how- 

 ever, when the larvae reach a length of 3.0 mm 

 the base and blade portions of each fin are begin- 

 ning to differentiate. From this stage until the 

 initiation of notochord fiexion at 6.0 mm the 

 rayed portion of the fin enlarges rapidly to form 

 the large fan-shaped structure characteristic of 

 Sebastolobus. At this stage the fin length is about 



17% of the body length. This increases to an av- 

 erage of 22% during notochord flexion and 27% in 

 post-flexion larvae up to 10 mm length. 



In specimens larger than 10 mm the relative 

 length of the pectoral fin differs considerably be- 

 tween S. altiuelis and S. alascanus (Figure 9). In 

 specimens of S. altiuelis in the 10- to 20-mm size 

 range, the pectoral fin length averages 34% of the 

 body length (range of 29 to 39% h The pectorals 

 reach their maximum relative length in 20- to 

 40-mm pelagic juveniles where they average 39% 

 of the body length (range of 35 to 41%). In pelagic 

 juveniles 40 to 50 mm long the average is 35% 

 (range of 32 to 37% ), and the fins are still shorter 

 in early benthic juveniles 42 to 60 mm long where 

 they average 29^7r of the body length (range of 25 



876 



