800 



Abstract— Otoliths from blue rockfish 

 (Sebastes mystinus), were aged by 

 using a combination of surface and 

 break-and-burn methods. The samples 

 were collected between 1978 and 1998 

 off central and northern California. 

 Annual growth increments in the oto- 

 liths were validated by using edge 

 analysis for females up to age 23 and for 

 males to age 25. The first annual growth 

 increment was identified by comparing 

 the diameter of the otolith from fish 

 known to be one year old collected in 

 May (when translucent zone formation 

 was completed) to the mean diameter of 

 the first translucent zone in the otoliths 

 from older fish. Our estimated maxi- 

 mum ages of 44 years for males and 41 

 years for females were much older than 

 those reported in previous studies. Von 

 Bertalanffy growth models were devel- 

 oped for each sex. Females grew faster 

 and reached larger maximum length 

 than males. The growth models were 

 similar to those generated in other 

 studies of this species in southern and 

 central California. Fish from northern 

 and central California had similar 

 maximum sizes, maximum ages, and 

 growth model parameters. 



Age and growth of blue rockfish 

 {Sebastes mystinus) from central and 

 northern California 



Thomas E. Laidig 

 Donald E. Pearson 



Southwest Fisheries Science Center 

 National Marine Fisheries Service 

 1 10 Shaffer Rd, 

 Santa Cruz, California 95060 

 E-mail lorn, laidig@noaa.gov 



Lorraine L. Sinclair 



Pacific States Manne Fisheries Commission 



411 Burgess Drive 



Menio Park, California 94025 



Manuscript approved for publication 

 17 April 2003 by Scientific Editor 



Manuscript received 26 June 2003 at 

 NMFS Scientific Publications Office. 



Fish Bull. 101:800-808. 



Accurate information on age and 

 growth is critical for reliable assess- 

 ments and effective management of 

 fish stocks. Most assessments of west 

 coast groundfish stocks use age-based 

 models (PFMC, 2001). It is important 

 to obtain reliable ages for maturity 

 schedules, age-specific fecundity, and 

 age-specific selectivity, as well as esti- 

 mates of aging accuracy, in order to 

 correctly estimate biomass and accept- 

 able biological catch numbers for these 

 assessments. Inaccurate age estimates 

 can lead to over-harvesting or denial of 

 fishing opportunities. 



In the present study, we examine 

 age and growth of blue rockfish (Se- 

 bastes mystinus). The blue rockfish is a 

 schooling species that occurs from Sitka 

 Strait (southeast Alaska) to northern 

 Baja California (Love et al., 2002). 

 They reach a maximum size of 508 

 mm fork length (FL). Blue rockfish are 

 frequent inhabitants of nearshore rocky 

 reefs, and are commonly found from the 

 surface to about 90 m water depth. Blue 

 rockfish comprise a major fraction of the 

 recreational fishery off California (Mill- 

 er and Geibel, 1973; Karpov et al., 1995) 

 but are less common in the commercial 

 fishery. In 1994, blue rockfish landings 

 off California totaled 172 metric tons 

 (t) from recreational fisheries and only 

 68 t from commercial fisheries (Rogers 

 etal, 1996). 



Age structure of blue rockfish has 

 been determined previously by using 



length-frequency analyses, tag-and- 

 recapture studies, scales, and whole 

 otoliths (Wales, 1952; Miller and Gei- 

 bel, 1973; McClure, 1982; MacGregor, 

 1983; Karpov et al., 1995). We esti- 

 mated age by examining the surface 

 of whole otoliths and broken-and-burnt 

 cross sections of otoliths. Aging the 

 surface of whole otoliths is only effec- 

 tive for young rockfish (Six and Horton, 

 1977; Kimura et al., 1979; Chilton and 

 Beamish, 1982). The break-and-burn 

 technique (Chilton and Beamish, 1982) 

 is used widely for age determinations of 

 west coast groundfish (including Dover 

 sole [Microstomas pacificus], sablefish 

 [Anoplopoma fimbria], and numerous 

 species of rockfishes). 



We used edge analysis to verify the 

 annual periodicity of growth incre- 

 ments in the otoliths of blue rockfish. 

 Edge analysis and marginal increment 

 analysis have been used to validate an- 

 nual growth increments in numerous 

 species. In recent studies, Crabtree 

 and Bullock (1998) validated the first 

 seven annual growth increments in 

 black grouper, and Brown and Sump- 

 ton (1998) validated the ages of the 

 redthroat emperor off Australia. The 

 procedure has been used to validate 

 annual growth increments in many 

 rockfish species, including redfish, 

 (Mayo et al., 1981), yellowtail (Kimura 

 et al., 1979), shortbelly (Pearson et al., 

 1991), widow (Pearson, 1996), gopher, 

 and kelp rockfish (Lea et al., 1999). 



