Laidig et al.: Descriptions and growth of larval and juvenile Sebostes wilsoni 



461 



but these patterns can be easily separated by using 

 meristic characters. 



Pelagic juvenile pygmy rockfish have a distinctive 

 pigment pattern consisting of three body bars that can 

 be used to discriminate this species from other Sebastes 

 species. Yellowtail, halfbanded, and redstripe rockfish 

 are the only species that have a similar three-barred 

 pigment pattern (Matarese et al., 1989; Moser, 1996; 

 Laroche 1 ). Yellowtail rockfish can be distinguished by 

 the lack of cheek bars and the presence of body bars 

 that extend all the way to the ventral surface. Also, in 

 yellowtail rockfish, the body bars form at a larger size 

 than in pygmy rockfish. In halfbanded rockfish, the 

 most anterior body bar is more densely pigmented than 

 the other bars and typically forms a diamond shape. 

 The caudal body bar is much wider and covers the en- 

 tire peduncle. Redstripe rockfish are the most similar 

 and are difficult to separate from pygmy rockfish by 

 using pigmentation alone. However, these two species 

 can be separated with greater than 90% certainty by 

 using meristic counts. Pygmy rockfish have a mean 

 anal-fin ray count of 6 (95% from the present study, and 

 93% from Laroche 1 ), whereas redstripe rockfish have an 

 average of 7 anal-fin rays (100% from Chen, 1986; 97% 

 from Laroche 1 ). 



It should be noted that the only illustration of pygmy 

 rockfish prior to our study was a 35.0-mm pelagic juve- 

 nile by Laroche, 1 which showed several pigment differ- 

 ences from our specimens of equivalent size. Laroche's 

 illustrated specimen had only faint body barring, no 

 cheek bars, and no ventral pigment, whereas all our 

 specimens had prominent body barring, at least one 

 cheek bar, and ventral pigment along the anal-fin ar- 

 ticulations. At this time we cannot determine whether 

 these differences were due to geographic variability in 

 pigment patterns (Laroche's specimen probably was 

 collected farther north than all of our specimens), or 

 a misidentification of the original specimen illustrated 

 by Laroche. 1 



The identification of larval and pelagic juvenile pygmy 

 rockfish used in our study was confirmed by using DNA 

 sequence analyses. Previous molecular identifications 

 and subsequent descriptions of juvenile starry rockfish 

 (S. constellatus) and swordspine rockfish (S. ensifer) 

 also were based on mitochondrial cytochrome b data 

 (Rocha-Olivares et al., 2000). In our study, orthologous 

 cytochrome b sequence was sufficient for identifica- 

 tion purposes, particularly for those specimens exhibit- 

 ing exact haplotype matches to reference adult pygmy 

 rockfish (e.g., FT2/FT3: 0.0% sequence divergence). 

 Relatively low levels of interspecific genetic variation 

 occurred between larval specimens and several refer- 

 ence species (pygmy, sharpchin. harlequin, and Puget 

 Sound rockfish, and, to a lesser extent, redstripe rock- 

 fish). Rocha-Olivares et al. (1999a) used control region 

 sequence, in addition to cytochrome b, to resolve phy- 

 logenetic relationships among recently diverged species 

 of the Sebastes subgenus Sebastomus. In the present 

 study, the control region sequence was used to increase 

 divergence levels between species and to aid in insur- 



ing correct molecular identifications of specimens FT1 

 and FT4. Species assignment to pygmy rockfish was 

 supported by the smallest divergence (based on cyt-6 

 and cyt-6+CR) from reference pygmy rockfish compared 

 with the other Sebastes species. 



Larval and juvenile pygmy rockfish can also be sepa- 

 rated from other Sebastes species by comparing the 

 radius of the extrusion check on their otoliths. Of the 

 fourteen other Sebastes species or species complexes 

 with measured otolith extrusion check radii ( Laidig and 

 Ralston, 1995; Laidig et al., 1996; Laidig and Sakuma, 

 1998), only four species and two complexes have radii 

 close to the average extrusion check radii for pygmy 

 rockfish (10.5 nm, SD = 0.3). Stripetail rockfish (S. saxi- 

 cola) had an average extrusion check radius (11.6 (im, 

 SD = 0.5) that was larger than the largest radius for 

 pygmy rockfish (11.0 (jm). Quillback rockfish (S. ma- 

 liger) had an average extrusion check radius of 9.1 jim 

 (SD = 0.1). which was smaller than the smallest radius 

 for pygmy rockfish (9.5 p.m). Species with extrusion 

 check radii similar to pygmy rockfish were kelp rockfish 

 (S. atrovirens) at 10.6 ^m (SD = 0.2), blue rockfish at 

 10.9 /./m (SD = 1.1), and the copper rockfish (S. caurinus, 

 extrusion check radius = 10.5 /jm; SD = 0.4) and gopher 

 rockfish (S. carnatus, extrusion check radius = 10.6 ,um; 

 SD = 0.3) complexes (see Laidig et al., 1996. for complex 

 definitions). Of these species, the only one that would be 

 confused with pygmy rockfish, by pigmentation alone, 

 would be blue rockfish at small sizes. However, pygmy 

 rockfish and blue rockfish are easily separated by using 

 meristic characters. 



Growth rates of larval rockfish generally are slow 

 during the first month of life and increase thereafter 

 (Laidig et al., 1991; Sakuma and Laidig, 1995; Laidig 

 et al., 1996). Because the youngest fish in our study 

 was estimated to be 40 days old, our linear model can 

 not be used to estimate early larval growth rates. For 

 pygmy rockfish older than 40 days, the growth rate of 

 0.28 mm/day was somewhat slower than that observed 

 for other Sebastes. Woodbury and Ralston (1991) found 

 that, for fish older than 40 days, growth rates varied 

 from 0.30 for widow rockfish (S. entomelas) to 0.97 mm/ 

 day for bocaccio. Other species exhibiting slightly faster 

 growth rates after 40 days of age include stripetail 

 rockfish (0.37 mm/day; Laidig et al., 1996), grass rock- 

 fish (S. rastrelliger; 0.36 mm/day; Laidig and Sakuma, 

 1998), and shortbelly rockfish (S. jordani; 0.53 mm/day; 

 Laidig et al., 1991). Yellowtail rockfish had a more 

 similar growth rate, ranging from 0.19 to 0.46 mm/day 

 (Woodbury and Ralston, 1991). These differences in 

 growth may reflect genetic variability or responses to 

 environmental variables. Woodbury and Ralston (1991) 

 suggested that annual variability in growth rates of 

 juvenile rockfish was related to year-to-year changes 

 in environmental conditions, especially temperature. 

 Boehlert (1981) determined that temperature greatly 

 affected growth rate of young splitnose rockfish (S. dip- 

 loproa) in the laboratory. Boehlert and Yoklavich (1983) 

 observed slower growth rates for black rockfish in colder 

 temperatures. Lenarz et al. (1991) analyzed the vertical 



