Laidig et al.; Relationship between abundance of juvenile Sebastes spp. and environmental variables 



43 



with the unique pattern in abundance of black rockfish, 

 especially in contrast to yellowtail rockfish. 



Correlations varied between the log-transformed 

 abundance indices and the monthly means of the 

 oceanographic variables (Table 3). All three species 

 were significantly and negatively correlated with sea 

 level anomaly during some of the months from Janu- 

 ary to June. For nearshore monthly temperature, there 

 was a similar pattern of negative correlation with in- 

 dex for all species during January to June. Only blue 

 rockfish were significantly correlated (P<0.001, r=0.58) 

 with offshore Ekman Transport, and only in Febru- 

 ary (Table 3). Months of high nearshore temperature 

 or sea level anomaly resulted in low juvenile rockfish 

 abundances. For example, when the abundance index 

 for blue rockfish was compared with sea level anomaly 

 in February (Fig. 3), years of highest abundance of blue 

 rockfish were always years of low sea level anomaly 

 (i.e., 1985, 1987, 1988, 2001, and 2002), but years of low 

 sea level anomaly did not always lead to particularly 

 high rockfish abundance (i.e., 1989). However, years of 

 highest sea level anomaly (e.g., 1983, 1992, and 1998) 

 resulted in the lowest blue rockfish abundance. 



The results of the CCA also indicate that low annual 

 abundance was associated with years of high nearshore 

 temperatures and high sea level anomaly. The first 

 canonical correlation was 0.57, which was significantly 

 different from zero (P<0.0001), and explained 97 % of 

 the covariance between the two data sets. The remain- 

 ing two canonical correlations were not significant and 

 explained little of the variability. Blue, yellowtail, and 

 black rockfish were negatively correlated with the first 

 canonical variable for the oceanographic data set (-0.43, 

 -0.45, and -0.55, respectively; Fig. 4). This indicates 

 that fish abundances were low when temperatures and 

 sea level anomalies were high. 



Blue rockfish annual abundance 





x=25-1 

 SD=45.2 





= =  



Jl 



I 



S3 M es B6 87 



90 9I9293W9S96 97 989900 0I 



S3 B4 85 ee a? 88 S9 90 31 9£ 93 



Black rockfish annual abundance 



x=3.5 

 SD=5.0 



jiil 



i.E 



Itail 



83 B4 as 86 87 88 89 90 91 92 93 W 95 96 97 98 99 00 01 02 03 



Year 



Figure 2 



Mean annual juvenile rockfish abundance index 

 for all one-minute surveys in two kelp beds for 

 blue iSebastes mystinus), yellowtail (S. flavidus), 

 and black (S. melanops) rockfish by year. Note the 

 different scale for black rockfish. Error bar=one 

 standard error. The 21-year mean (represented by 

 a dashed line) and the standard deviation for each 

 species are given on each plot. The sample size for 

 each year is reported in Table 1. 



The data for year-class strength of commercially 

 caught adult yellowtail rockfish corresponded with the 

 annual abundance index for juvenile yellowtail rockfish 

 (Table 4), and were significantly correlated for all ports 

 combined for 1997 (P<0.01, n= 29, r=0.48) and 1999 

 (P<0.04, n = 31, r=0.36), but not for 1998 {P<0.1, n=21, 

 r=0.37). For 1997, juvenile rockfish abundance was sig- 

 nificantly correlated with adult fish numbers at Bodega 



