LAROCHE and RICHARDSON: DEVELOPMENT OF LARVAE AND JUVENILES OF ROCKFISHES 



final stage of notochord flexion, which is completed 

 by ~9 mm. Transformation from postflexion larva 

 to pelagic juvenile occurs between -13.5 and 20 

 mm as indicated by structural change of the dorsal 

 and anal fin prespines to sharp, hard spines. 

 Melanistic pigmentation gradually increases 

 along the dorsal body surface under the dorsal fins 

 and along the lateral midline of the caudal pedun- 

 cle through the larval and transformation periods. 

 A more rapid increase in pigment over the body, 

 progressing anterior to posterior, is initiated at the 

 beginning of the pelagic juvenile stage ( —20 mm). 

 Transition from pelagic to benthic habitat takes 

 place at lengths somewhere between 35 and 65 

 mm. The largest pelagic juvenile was 65.0 mm. 

 Because of the long-term pelagic sampling effort 

 off Oregon and the lack of specimens in the 35-65 

 mm length range, it seems likely that this species 

 transforms at a relatively small size (=35-40 

 mm). Small benthic juveniles would not be re- 

 tained in the large mesh bottom trawls. The small- 

 est benthic juvenile observed was 65.0 mm long. 



Morphology (Tables 2, 6). — Various body parts 

 were measured on 51 selected specimens of S. 

 zacentrus (7.4-74.8 mm). Relative grovd:h trends 

 are summarized in Table 2. 



This is a relatively deep-bodied form with body 

 depth 359f SL in flexion larvae, decreasing to 30% 

 in pelagic juveniles. It also has a rather large head, 

 averaging 40-43% SL during the larval and trans- 

 forming periods. 



Fin Development (Tables 2, 5, 6).— The adult 

 complement of 16-18, usually 17, pectoral fin rays 

 is present in the smallest larva (7.4 mm). The 

 pectoral fin is of moderate length, increasing from 

 15.3% SL in flexion larvae to 26.7 and 

 26.4% SL in pelagic and benthic juveniles, 

 respectively. 



The adult complement of pelvic fin spine and 

 rays (1,5) is present on the smallest larva. The 

 pelvic fin is moderately long increasing from 13.7 

 to 21.3% SL between flexion and benthic juvenile 

 stages. The pelvic spine is also of mod- 

 erate length, reaching 20% SL in transforming 

 larvae. 



The adult complement of 8 + 7 principal caudal 

 fin rays can be counted on the smallest larva. Five 

 benthic juveniles, =65-75 mm, had superior and 

 inferior secondary caudal fin rays, respectively: 

 10/11 (three specimens) and 11/10 (two specimens), 

 as determined from radiographs. 



Dorsal fin spines and rays, including prespines, 

 are completely formed by =8 mm but developing 

 elements are countable in the smallest larva (7.4 

 mm). The dorsal and anal fin prespines become 

 spines by =15.5 and 20 mm, respectively, marking 

 the beginning of the pelagic juvenile stage. 



Spination (Tables 2, 7). — Spines on the left side of 

 the head of the smallest S. zacentrus include the 

 parietal; nuchal; first and third anterior preoper- 

 cular spines; first, second, third, fourth, and fifth 

 (as a bump) posterior preopercular spines; 

 superior opercular spine (as a bump); postocular; 

 first inferior infraorbital; first superior infraorbit- 

 al; pterotic; and the inferior posttemporal spine. 



The parietal spine and ridge are serrated on all 

 specimens <36 mm long. The relatively long (23% 

 HL) parietal spine decreases in prominence to 

 = 3% HL by the benthic juvenile stage. The nuchal 

 spine is always smaller than the parietal and is 

 completely fused to it in benthic juveniles. 



All five posterior preopercular spines are pres- 

 ent as sharp spines by 8.5 mm and persist in 

 adults. The third spine is relatively long (33% HL 

 in flexion larvae) and decreases in length with 

 development to 4% HL in benthic juveniles. Serra- 

 tions are present on the first anterior preopercular 

 spine of specimens <22 mm long, on the first and 

 second posterior preopercular spines on specimens 

 <26.5 mm, and on the third posterior preopercular 

 spine to =34 mm. The first and third anterior 

 preopercular spines are reduced to blunt bumps by 

 = 25 mm and are absent on all specimens >26.3 

 mm. 



The superior opercular spine is sharp tipped by 

 = 8 mm. The inferior opercular spine appears as a 

 blunt bump at =8 mm and becomes a sharp tipped 

 spine by =13 mm. The interopercular spine ap- 

 pears as a blunt bump by =8 mm and as a small, 

 sharp spine in all specimens >12 mm. The sub- 

 opercular spine appears as a blunt bump by = 13 

 mm, is usually present as a short, sharp spine 

 between 13 and 23 mm, is reduced to a blunt bump 

 on specimens 23-26 mm, and is usually absent on 

 specimens >26 mm. 



The ridge anterior to the postocular spine is 

 serrated on specimens <27 mm. The preocular 

 spine appears as a blunt bump at 14 mm and usu- 

 ally as a moderately strong, sharp spine on most 

 specimens >15 mm. The first inferior infraorbital 

 spine is present as a sharp spine on all specimens 

 to 35 mm and as a blunt bump in the benthic 

 juveniles examined (65.0-74.8 mm). The second 



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