MOSER: DEVELOPMENT AND DISTRIBUTION OF SEBASTOLOBUS 



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Figure 6. — Juveniles oi Sebastolobus alascanus. Above, 25.3-mm newly transformed benthic juvenile from bottom trawl. Below, 



50.3-mm benthic juvenile from bottom trawl. 



to 33^). The pectoral fins ofS. alascanus are con- 

 siderably shorter than those of S. altivelis at 

 comparative sizes. In specimens 10 to 20 mm long 

 fin length averages 29% of body length (range of 

 26 to 31%). In 10- to 27-mm pelagic specimens 

 pectoral fin length averages 29% of the body 

 length (range of 26 to 32%). In early benthic 

 juveniles 22 to 60 mm long, fin length is reduced 

 to an average of 24% (range of 23 to 28%). The 

 pectoral fin in pelagic juveniles of S. macrochir is 

 even longer than in S. altivelis. In 21- to 30-mm 

 specimens fin length averaged 43% of the body 

 length (range of 40 to 44%). 



The depth of the pectoral fin base is a particu- 

 larly useful character in distinguishing the lar- 

 vae of Sebastolobus from those of Sebastes and is 

 also useful in separating the two species of 

 Sebastolobus (Figure 10). In larvae of Sebastes 



examined (e.g., S. paucispinis) the depth of the 

 fin base is about 9 or 10% of the body length 

 through notochord flexion; thereafter it gradually 

 diminishes, relative to body length, to about 5 or 

 6% in the smallest pelagic juveniles. In Sebas- 

 tolobus there is an opposite trend of relative in- 

 crease from an average of ll%f (range of 10 to 

 15% ) in pre-flexion larvae, to 18% (range of 15 to 

 20%) in subsequent stages of S. altivelis up to 

 about 40 mm in length. In larger pelagic 

 juveniles of S. altivelis the depth of the pectoral 

 fin base begins to decrease in relation to body 

 length. In 40- to 50-mm specimens the average is 

 16.5% (range of 15 to 18%) and in 50- to 56-mm 

 pelagic juveniles it is 15% (range of 15 to 16%). It 

 is further reduced to 14% (range of 13 to 15%) in 

 42- to 60-mm benthic juveniles. The pectoral fin 

 base in S. alascanus is significantly shallower 



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