530 



Fishery Bulletin 89(3). 1991 



c » 



I) 



3 20 



Shortbelly 



1983 N - 99 



1984 N = 1.526 



1985 N = 5.875 



1986 N - 6,0+8 



JL 



1987 N - 6.579 



■™- - 



1988 N - 3.921 



"LA 



Bocaccio 



1 984 N = 353 



1985 N = 21 



AL 



1986 N - 357 



1987 N-217 



1988 N - 210 



Chilipepper 



Widow 



Yellowtail 



1985 N - 79 



1986 N - 62 



1987 N - 903 



Jlw 



1 988 N - 738 



JUv 



1985 N = 3.296 



1986 



1987 N = 821 



19B8 N - 390 



1985 N - 306 



1986  N = 44 



1987 N = 124 



1988 N = 166 



1 



k J« Fab Mor Apr May Da Jon Fab Mar Apr May Oao Jon Fob Mar Apr May Doc Jon Fob Mor Apr May Doc Jon Fob Mor Apr May 



Back-calculated Birthdate 



Figure 9 



Composite annual back-calculated birthdate distributions of shortbelly, bocaccio, chilipepper, widow, and yellowtail rockfishes 

 (1983-88). 



species (bocaccio and shortbelly rockfish), 1984 pro- 

 duced faster growth than in any other year. 



Overall, growth performance shows remarkable 

 coherency in this time series. This conclusion is further 

 reinforced with results from principal component 

 analysis. Following ordination, 83.3% of the variation 

 in growth-performance standard scores was accounted 

 for by the first principal component (A. 4.16). First 

 component scores (£.) for each year were ranked in 

 descending order as follows: 1987 (^ 2.74) > 1986 (£■ 

 0.36)>1988 (£i - 1.40)>1985 fo - 1.71). These values 

 follow the general pattern evident in Figure 8. 



Back-calculated birthdate distributions 



As with the aged subsample data, the birthdate fre- 

 quency distributions that were generated from length- 



frequency data were pooled across sweeps within each 

 year, even though in some cases significant differences 

 occurred. Although sweep-to-sweep differences would 

 be useful in elucidating within-season patterns of mor- 

 tality, movement, and growth, we ignored them be- 

 cause an analysis of the components of variance showed 

 that, with the exception of yellowtail rockfish, varia- 

 tion of this kind was quite minor in comparison to 

 yearly fluctuations in birthdate distributions. 



Results of back-calculating time of birth (Fig. 9) 

 show that, typically, surviving juveniles were born dur- 

 ing a two-month period. For most species-year com- 

 binations, a unimodal distribution is evident. Bocaccio 

 display somewhat broader birthdate distributions than 

 the other species, perhaps reflecting their multiple 

 spawning capability in southern California waters 

 (MacGregor 1970). Positive skewness in the birthdate 



