DEVELOPMENT AND GEOGRAPHIC DISTRIBUTION OF THE ROCKFISH, 



SEBASTES MACDONALDI (EIGENMANN AND BEESON, 1893), 



FAMILY SCORPAENIDAE, OFF SOUTHERN CALIFORNIA 



AND BAJA CALIFORNIA 



H. Geoffrey Moser' 



ABSTRACT 



The larval and juvenile stages of the scorpaenid fish, Sebastes tnacdonaldi, are described 

 and illustrated. The sequence of ossification of bones and cranial spines in larvae is 

 described in detail. S. macdonaldi appears to have the most southerly distribution of any 

 species of Sebastes in the eastern north Pacific. The geographic distribution and sea- 

 sonal abundance of S. macdonaldi larvae are discussed and compared with published 

 information On the adults. 



The genus Sebastes is represented by 65 species 

 in the eastern north Pacific (Chen, 1971). Al- 

 though all members of the genus are ovoviyip- 

 arous and have a planktonic larval stage, they 

 exhibit a remarkable diversity in morphology, 

 color, and mode of existence. They rank first in 

 total numbers of fish landed annually by the Cal- 

 ifornia sport fishing fleet (Young, 1969) and are 

 a major commercial resource (Heimann and 

 Frey, 1968). Despite their obvious importance, 

 information on the complete life histories of all 

 but a few species is fragmentary or nonexistent. 

 At present a complete life history series (embry- 

 onic, larval, juvenile, and adult stages) has been 

 described for only a single eastern Pacific spe- 

 cies, S. paucispinis (Moser, 1967); however, 

 young-stage larvae attained from pregnant fe- 

 males have been illustrated for four species from 

 central California (Morris, 1956), for nine spe- 

 cies from the Pacific northwest (DeLacy, Hitz, 

 and Dryfoos, 1964), and for 14 additional rock- 

 fishes from southern California and Baja Cali- 

 fornia (Moser, 1967). Recently, Waldron (1968) 

 has described the early larvae of S. pinniger. 



Ahlstrom (1961, 1965, 1969) has shown that 

 rockfish larvae are the third or fourth most 



^ National Marine Fisheries Service, Southwest Fish- 

 eries Center, La Jolla, CA 92037. 



abundant kind of larvae collected annually in the 

 plankton surveys of the California Cooperative 

 Oceanic Fisheries Investigations (CalCOFI). 

 Early juvenile rockfish, like the larvae, are pe- 

 lagic but evade plankton nets easily and must 

 be collected by other means. For example, some 

 species are attracted to bright lights at night 

 and can be dipnetted at the surface. Also, some 

 species associate with floating objects (Hitz, 

 1961) and with drifting kelp (Mitchell and Hunt- 

 er, 1970) and may be collected when these are 

 brought aboard ship. Finally, pelagic juveniles 

 occasionally appear in midwater trawl samples 

 (Berry and Perkins, 1966; Lavenberg and Fitch, 

 1966). Demersal juveniles are common con- 

 stituents of otter trawl catches in coastal waters. 

 Larvae of S. macdonaldi have such a distinc- 

 tive melanophore pattern that a developmental 

 series was established before it could be identi- 

 fied to species. The extreme southerly distribu- 

 tion of these larvae in the CalCOFI pattern 

 provided a clue to their identity, since adults of 

 S. macdonaldi have been collected farther south 

 along Baja California than any other species of 

 Sebastes (Chen, 1971). A comparison of intra- 

 ovarian larvae from pregnant S. macdonaldi 

 with the smallest individuals from plankton col- 

 lections provided definitive evidence of the iden- 

 tity of the larval series. Juvenile stages critical 



Manuscript accepted October 1971. 



FISHERY BULLETIN: VOL. 70. NO. 3, 1972. 



941 



