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Fishery Bulletin 105(1) 



(1993), using seabird diet to assess the abun- 

 dance of juvenile rockfishes, also reported the 

 greatest abundance of rockfishes in years of 

 intermediate upwelling. Yoklavich et al. (1996) 

 and Johnson et al. (2001) observed that, dur- 

 ing years when upwelling was delayed, those 

 rockfishes released later in the year had in- 

 creased survivorship. In addition, Fasten et 

 al. (2003) observed that monthly tidal cycles 

 were important in estimating the numbers of 

 newly recruited black rockfish (S. inermis) in 

 the western Pacific. 



In our study, we examined the relationship 

 between the annual abundance of juvenile rock- 

 fishes recruiting to the nearshore kelp beds off 

 northern California and three oceanographic 

 variables (sea level anomaly, nearshore temper- 

 ature, and offshore Ekman transport) over 21 

 years. Three species of juvenile rockfishes (blue, 

 yellowtail, and black rockfish, [S. melanops]) 

 were surveyed. Parturition (the release of lar- 

 vae from the mother) in these species occurs in 

 the winter and the resulting pelagic larvae and 

 juveniles spend between three to five months 

 in the offshore midwater environment (Love et 

 al., 2002). All juveniles of these species migrate 

 in mid to late spring and early summer from 

 the offshore pelagic environment to nearshore 

 midwater and benthic environments on or next 

 to rocky outcrops, commonly with dense algal 

 growth; this movement we define here as juve- 

 nile recruitment (Anderson, 1983). 



Materials and methods 



Surveys of young-of-the-year (YOY) rockfishes 

 were conducted annually between 1 July and 15 Sep- 

 tember from 1983 to 2003 within two kelp beds along 

 the northern California coast (Dark Gulch [39°14'N; 

 123°46'W] and Salmon Point [39°12'N; 123°46'W]) in 

 Mendocino County (Fig. 1). Each kelp bed included 

 high-relief bedrock interspersed with low-relief cobble 

 and sand areas. They were bounded by shoreline on two 

 sides, a sand channel on one side, and deep water on the 

 remaining side, and thus each kelp bed was isolated. 



Strip transects were conducted by using SCUBA. 

 Researchers swam in one direction 2 m above the sea 

 floor and counted all juvenile rockfishes within 3 m in 

 any direction for one minute. At the end of each one- 

 minute survey, the numbers of each species were re- 

 corded. The researcher would then haphazardly choose 

 another direction to swim and conduct rockfish counts 

 for another minute. Surveys were made throughout the 

 kelp bed at both sites from the surface to 20 m. YOY 

 rockfishes were distinguished from older conspecif- 

 ics by their size (less than 80 mm standard length 

 in August) and from other rockfish species by body 

 shape and pigment patterns (Anderson, 1983; Love et 

 al., 2002). 



Figure 1 



The survey sites in Mendocino County, California. Dark Gulch 

 and Salmon Point kelp beds are represented by the stars. 



Surveys were conducted only when appropriate condi- 

 tions occurred. First, surveys were conducted between 

 the hours of 0900 and 1700 to standardize light condi- 

 tions. Second, surveys were made only when underwater 

 visibility was greater than 4 m. Underwater visibility 

 was measured by Secchi disk, transect line, and by 

 estimating the distance at which objects (i.e., fishes 

 and rocks) could be seen. Third, swell height had to be 

 less than 2 m for diver safety and to standardize sea 

 conditions. 



An index of annual abundance (index) for each spe- 

 cies of juvenile rockfish was computed by pooling 

 all one-minute surveys for a year at each study site, 

 and dividing by the total number of one-minute sur- 

 veys for that year. We used a paired t-test to compare 

 species-specific indices between the two study sites. 

 Data were log-transformed to equalize the variance 

 among years. We used cross-correlation analysis to 

 examine patterns in the index among species. For no 

 time series (either biological or environmental) was 

 there a significant autocorrelation present. Therefore, 

 our observations complied with the assumption of 

 independence. 



