Abstract.- Young-of-the-year 

 pelagic juvenile rockfish (genus Se- 

 bastes) were collected during annual 

 surveys in the spring and early sum- 

 mer, 1983-88, off the central Califor- 

 nia coast. Growth rates and back- 

 calculated birthdate distributions of 

 five species (shortbelly rockfish S. 

 jordani, bocaccio S. paucispinis, 

 chilipepper S. goodei, widow rockfish 

 S. entomelas, and yellowtail rockfish 

 S. flavidus) were estimated from 

 daily otolith increments. 



Interspecific variation in growth 

 rates was evident, with bocaccio ex- 

 hibiting the fastest growth (0.56- 

 0.97 mm/day) and yellowtail rockfish 

 growing slowest (0.19-0.46 mm/day). 

 Growth rates of all species varied 

 among years. Comparisons of annual 

 growth performance, measured by 

 predicting standard length at a se- 

 lected standard age, revealed strong 

 positive interannual covariation 

 among the five species studied; in 

 general, growth was relatively good 

 in 1987 and was poor in 1985. 



Back-calculated birthdate distribu- 

 tions also revealed strong positive in- 

 terannual covariation among these 

 species; most distributions were uni- 

 modal. The years 1985 and 1988 

 were characterized by distributions 

 that were centered early in the year; 

 whereas in 1986 (and possibly in 

 1983) these distributions occurred 

 later. 



Interannual Variation in Growth 

 Rates and Back-Calculated Birthdate 

 Distributions of Pelagic Juvenile 

 Rockfishes [Sebastes spp.) off 

 the Central California Coast 



David Woodbury 

 Stephen Ralston 



Tiburon Laboratory, Southwest Fisheries Science Center 



National Marine Fisheries Service, NOAA 



3 1 50 Paradise Drive, Tiburon, California 94920 



Manuscript accepted 20 February 1991. 

 Fishery Bulletin, U.S. 89:523-533 (1991). 



Understanding recruitment fluctua- 

 tions and the interplay of factors af- 

 fecting the establishment of year-class 

 strength is the single most challeng- 

 ing issue in fisheries today (Roths- 

 child 1986). In particular, rockfishes 

 of the genus Sebastes are known to 

 exhibit large fluctuations in recruit- 

 ment (Leaman and Beamish 1984), 

 wherein a single dominant year-class 

 can sustain a fishery for a number of 

 years. Rockfishes are an important 

 component of the west coast ground- 

 fish fishery, with combined 1988 

 landings of 35,000 MT (PFMC 1989). 

 Historically, rockfish stock assess- 

 ments have relied almost exclusive- 

 ly on catch-at-age data (e.g., High- 

 tower and Lenarz 1989); such analyses 

 do not perform well in the absence of 

 auxiliary information (e.g., an index 

 of pre-recruit abundance). Knowledge 

 of mechanisms affecting first-year 

 survival could improve our ability to 

 predict recruitment, which in turn 

 could have major implications to the 

 management of this group (Deriso 

 etal. 1985, Methot 1989, but see 

 Walters 1989). 



In some situations starvation and 

 food limitation have been shown to 

 control larval abundance (Lasker 

 1981), although predation is believed 

 to be important in others (reviewed 

 in Sissenwine 1984, Bailey and Houde 

 1989). In either case, if mortality 



decreases with increasing size (Miller 

 et al. 1988), larval and pelagic juve- 

 nile growth rates can have a major 

 impact on survivorship during the 

 first year of life. This is because fast- 

 growing fish are exposed to high 

 mortality rates for shorter periods of 

 time (Houde 1987). 



As part of an ongoing study to 

 monitor annual fluctuations in the 

 abundance of young-of-the-year pela- 

 gic juvenile rockfishes inhabiting the 

 coastal waters off central California, 

 the growth of five species (shortbelly 

 rockfish S. jordani, bocaccio S. pau- 

 cispinis, chilipepper S. goodei, widow 

 rockfish S. entomelas, and yellowtail 

 rockfish S. flavidus) was assessed 

 through the study of otolith daily- 

 increment microstructure formed 

 during the pelagic larval and juvenile 

 life stages (Jones 1986). Intraspecific 

 differences in growth performance 

 over the period 1983-88 were then 

 examined statistically and trends 

 were compared among species. 



Birthdate frequency distributions 

 of the fish that survived from birth 

 to the time of sampling were back- 

 calculated from aged subsamples, 

 length measurements, and known 

 dates of capture (Bolz and Lough 

 1983). These projected distributions 

 were compared intraspecifically 

 among years to evaluate whether the 

 preponderance of juvenile survivors 



523 



