MOSER: DEVELOPMENT AND DISTRIBUTION OF SEBASTOLOBUS 



Table 8. — Mean lengths with standard deviations in mm (A) and size ranges in mm (B) of Sebastolobus 

 larvae taken during 2 yr of the California Cooperative Oceanic Fisheries Investigations. 



by large pelagic juveniles from the previous 

 year's spawning season. A single size class of 

 transforming specimens is present in October and 

 November, however, the absence of the large 

 pelagic juveniles is probably due to inadequate 

 sampling, since they are present in December. 

 From January through April a single class of 

 pelagic juveniles is present. In summary, the 

 early life history of S. altiuelis is as follows: lar- 

 vae are produced in a 4- or 5-mo spawning season 

 that peaks in April. Transformation into pelagic 

 juveniles begins as early as July and by the end of 

 December most have completed transformation. 

 The prolonged pelagic juvenile stage lasts until 

 the following summer when the juveniles begin 

 to settle to the bottom. This process probably ex- 

 tends over a 6- to 8-mo period with some juveniles 

 remaining pelagic until December. The total 

 period spent in the pelagic environment from 

 spawning to settling is about 20 mo. The means of 

 the composite monthly length frequencies are 

 plotted in Figure 14 to give an estimation of 

 growth of this species. 



The composite monthly length frequencies for 

 mid-water trawl-caught specimens of S. alas- 

 canus are shown in Figure 15. In contrast to 

 S. altivelis, only a single size class is present 

 each month. From July to December a single 

 class of larval and transitional specimens less 

 than 20 mm long is present. Some pelagic 

 juveniles are present in December and by 

 January most of the specimens have completed 

 transformation. Successive samples from Feb- 

 ruary to May contain only pelagic juveniles. In 

 summary, the planktonic and early pelagic life 

 history of S. alascanus is similar to that of S. 



altivelis. A probable 4- or 5-mo spawning period 

 that peaks in April gives rise to larvae that ap- 

 pear in mid-water trawl samples in summer. 

 Transformation into the pelagic juveniles begins 

 as early as August and most have completed 

 transformation by the end of December. A class of 

 pelagic juveniles is present from December 

 through May, however, the size ranges for these 

 months overlap the range at which S. alascanus 

 juveniles begin to settle to the bottom, and it is 



E 

 S 



I 

 o 



Q 



a: 

 < 



a 



z 

 < 



h- 

 tn 



Figure 14. — Means of composite monthly size frequencies of 

 larvae and pelagic juveniles of Sebastolobus altivelis and S. 

 alascanus from mid- water trawls. 



883 



