MOSER: DEVELOPMENT OF ROCKFISH 



ter series, composed of a single spine on each 

 lacrimal, infraorbital, and jugal element, forms 

 a shelf in late-stage larvae and in juveniles, but 

 usually only the lacrimal spine remains in adults. 

 The inferior series persists in adults and typi- 

 cally contains 3 to 5 spines. A nuchal spine 

 forms directly posterior to each parietal spine 

 in larvae about 8.0 mm long and persists in ju- 

 veniles and adults. Nasal spines are late to form 

 (15.0 mm) but also persist in adults. 



Two spines appear on each preopercle in 

 larvae 5.1 to 5.2 mm long. These are the third 

 and fourth members of a series of five preoper- 

 cular spines that forms throughout the larval pe- 

 riod (Table 5). The third preopercular spines 

 develop three longitudinal serrated ridges and 

 elongate rapidly to become the longest larval 

 spines. They reach a maximum length of 35 "^r 

 of the head length in larvae about 9.0 mm long 

 and then decline in relative length. The five 

 preopercular spines remain in juveniles and 

 adults, but the short spines which develop im- 

 mediately anterior to the second, third, and 

 fourth preoperculars (Table 5) become obsoles- 

 cent after the larval period. A pair of spines 

 forms at the posterior margin of each opercle 

 and persists in juveniles and adults. 



The supracleithral and cleithral spines develop 

 during the larval period; the supracleithral 

 spines form on the postemporal elements in lar- 

 vae about 7.7 mm long and the cleithral spines 

 form on the supercleithra at about 12.0 mm. 

 Both pairs persist into the adult stage. 



DISTRIBUTION 



S. macdonaldi has the most southerly distri- 

 bution of any species of Sebastes in the eastern 

 north Pacific. Chen (1971) lists its southern 

 range record as Morgan Bank off Baja Califor- 

 nia (lat 23°24.0'N, long 111°11.5'W) and reports 

 on the capture of a single adult specimen (LACM 

 8837-4) from Santa Inez Bay in the Gulf of Cal- 

 ifornia (lat 26°59.1'N, long 111°48.9'W). A col- 

 lection of six pelagic juveniles (32.7-44.4 mm 

 SL; LACM 8821-9) by midwater trawl from the 

 Ballenas Channel in the Gulf of California (lat 

 28°56.5'N, long 113°10.5'W) is reported herein. 

 Although the localities at Morgan Bank and 



Santa Inez Bay are separated by a distance of 

 approximately 1,000 km, it is likely that future 

 collections in this region will substantiate Chen's 

 (1971) suggestion that the outer coast and Gulf 

 of California populations are continuous. 



The southerly distribution of S. macdonaldi is 

 shown by the distribution of the larvae (Table 6, 

 Figure 5). For the 4 years examined, larvae 

 were taken as far north as CalCOFI line 90 and 

 as far south as line 137. Line 90, running south- 

 westerly from Dana Point, Calif., probably de- 

 limits the northern extent of reproduction for 

 this species, although an adult has been taken as 

 far north as Pt. Sur, Calif. (Phillips, 1961). 

 Total numbers of larvae and frequency of oc- 

 currence of larvae increase to the south of line 90. 



Figure 5. — Stations at which larvae of Sebastes mac- 

 donaldi were collected during 4 years (1953, 1960, 1965, 

 and 1966) of CalCOFI plankton surveys. Solid circles 

 indicate stations where number of Sebastes macdonaldi 

 larvae exceeded mean number (4.8) for all positive sta- 

 tions. Area of frequent occupancy is outlined (see 

 Ahlstrom, 1961, for complete grid). 



955 



