DEVELOPMENT OF EGGS AND LARVAE OF THE WHITE CROAKER, 



GENYONEMUS LINEATUS AYRES (PISCES: SCIAENIDAE), 



OFF THE SOUTHERN CALIFORNIA COAST 



William Watson 1 



ABSTRACT 



Eggs and larvae of the white croaker, Genyonemus lineatus, were collected near the San Onofre 

 Nuclear Generating Station in 1978 and 1979. A developmental series based on 59 eggs and 168 lar- 

 vae and early juveniles was assembled. 



Live G. lineatus eggs are pelagic, transparent, and spherical, averaging0.85 mm in diameter with 

 a single oil droplet of 0.23 mm. Preserved, newly hatched larvae average 1.57 mm SL and are not 

 well developed. Larval development is a gradual process. Notochord flexion begins at ca. 5.4 mmSL 

 and is complete by ca. 6.4 mm SL. Dorsal and anal fin anlagen appear at ca. 5 mm SL and the full 

 complement of rays is present in each fin by ca. 8.2 mm SL. Pelvic differentiation begins atca. 5.3 

 mm SL and is finished by ca. 8.6 mm SL. Pectoral rays begin to develop at ca. 7.8 mm SL and all are 

 present by ca. 13 mm SL. 



Larval pigmentation is largely restricted to the dorsum at hatching, but migrates to the ventral 

 midline during early development. Melanophores are restricted to the ventrum and gut through 

 much of the subsequent larval period. A barred pattern develops during transition to the juvenile 

 stage. 



Genyonemus lineatus larvae are distinguishable from similar cooccurring species by the presence 

 of a nape melanophore and larger melanophores in the midventral trunk series at myomeres 9-10 

 and 16-18. 



The sciaenid genus, Genyonemus, is represented 

 by a single species, G. lineatus (Ay res), the white 

 croaker. It occurs along the west coast of North 

 America from central Baja California to south- 

 ern British Columbia (Miller and Lea 1972), 

 although its numbers are reduced north of San 

 Francisco, Calif. (Frey 1971). In southern Cali- 

 fornia the white croaker is a common inshore 

 species of modest sport and commercial value 

 ( Skogsberg 1939; Frey 1971 ). Its larvae rank sec- 

 ond in abundance only to those of the northern 

 anchovy, Engraulis mordax, among the inshore 

 ichthyoplankters off San Onofre, Calif. (Walker 

 et al. 1980 2 ). 



Despite its abundance in southern California, 

 the early life history of G. lineatus is poorly 

 known. Seasonal spawning cycles are described 

 based on gonadal studies (Goldberg 1976), and 

 the duration of the egg stage is mentioned by 

 Morris (1956), who reared G. lineatus from field- 



1 Marine Ecological Consultants, 533 Stevens Avenue, Sol- 

 ana Beach, CA 92075. 



2 Walker, H.J., A. M. Barnett.andP.D. Sertic. 1980. Sea- 

 sonal patterns and abundance of larval fishes in the nearshore 

 Southern California Bight off San Onofre, California. Ma- 

 rine Ecological Consultants of Southern California, 533 

 Stevens Ave., Solana Beach, CA 92075, 16 p. 



collected eggs through 19-d-old larvae. Larvae 

 are not described, although Morris (1956) gives 

 dimensions of the egg. 



Beginning in January 1978, Marine Ecologi- 

 cal Consultants of Southern California initiated 

 a study of the inshore ichthyoplankton off San 

 Onofre (Fig. 1) for the Marine Review Commit- 

 tee of the California Coastal Commission (Bar- 

 nettand Sertic 1979 3 ). During this study approxi- 

 mately 48,000 G. lineatus larvae were sorted 

 from the samples, providing an opportunity to 

 construct a developmental series through the 

 early juvenile stage. Live plankton samples pro- 

 vided eggs for rearing purposes. This paper de- 

 scribes the egg and larval developmentof G. line- 

 atus as determined from these series. 



MATERIALS AND METHODS 



Egg and larval descriptions are based on de- 

 tailed observation of 59 eggs, 29 reared larvae. 



Manuscript accepted December 1981. 

 FISHERY BULLETIN: VOL. 80, NO. 3, 1982. 



'Barnett, A. M., and P. D. Sertic. 1979. Preliminary re- 

 port of patterns of abundance of ichthyoplankton off San 

 Onofre and their relationship to the cooling operations of 

 SONGS. Marine Review Committee Document 79-01, p. 1-1 

 to 4-5. Marine Review Committee of the California Coastal 

 Commission, San Francisco, Calif. 



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