Abstract. — Upwelling and its as- 

 sociated offshore advection of surface 

 waters can affect the recruitment of 

 nearshore organisms. Late-stage pelagic 

 Pacific and speckled sanddabs, Citha- 

 richthys sordidus and C. stigmaeus, were 

 collected with a midwater trawl off cen- 

 tral California during the spring and 

 summer upwelling season. In both spe- 

 cies, otolith size increased linearly with 

 metamorphic development; standard 

 length, however, increased asymptoti- 

 cally. Earlier stages of both species oc- 

 curred shallower in the water column, 

 whereas later stages occurred deeper. 

 The deeper distribution of later stages 

 may have been due to decreased buoy- 

 ancy as a result of increased otolith size 

 and ossification of bony structures co- 

 incident with metamorphosis. Earlier 

 stages of both species were more abun- 

 dant offshore and less abundant in ar- 

 eas of upwelling, whereas later stages 

 were more abundant nearshore regard- 

 less of upwelling. The difference in the 

 horizontal distributions of early and 

 late stages may have been passively 

 driven by different current patterns as a 

 result of the difference in vertical distri- 

 butions between early and late stages. 



Distribution of pelagic 

 metamorphic-stage sanddabs 

 Citharichthys sordidus and 

 C. stigmaeus within areas of 

 upwelling off central California 



Keith M. Sakuma 



Tiburon Laboratory, Southwest Fisheries Science Center 



National Marine Fisheries Service. NOAA 



3 1 50 Paradise Drive, Tiburon, California 94920 



Ralph J. Larson 



Department of Biology, San Francisco State University 

 1 600 Holloway Avenue, San Francisco, California 94 1 32 



Manuscript accepted 27 February 1995. 

 Fishery Bulletin 93:516-529 (1995). 



Pacific and speckled sanddabs, Ci- 

 tharichthys sordidus and C. stig- 

 maeus, are abundant along the Pa- 

 cific coast of North America (Miller 

 and Lea, 1976). In both species, 

 spawning peaks during the summer 

 months but also occurs at lower lev- 

 els during the remainder of the 

 year; individuals may spawn more 

 than once during a given season 

 (Arora, 1951; Ford, 1965; Goldberg 

 and Pham, 1987; Matarese et al., 

 1989; Rackowski and Pikitch, 1989). 

 Sanddabs have a long pelagic stage, 

 which may exceed 324 days in 

 speckled sanddabs and 271 days in 

 Pacific sanddabs (Kendall, 1992; 

 Brothers 1 ), and settle at a relatively 

 large size (20 to greater than 39 mm 

 standard length (SL) for Pacific 

 sanddabs and 24 to greater than 36 

 mm for speckled sanddabs) (Ahl- 

 strom et al., 1984; Matarese et al., 

 1989). Kramer (1990) noted that 

 flatfish with nearshore nurseries 

 had brief pelagic stages and settled 

 at small sizes, whereas those with 

 less restricted coastal nurseries had 

 longer pelagic stages and settled at 

 larger sizes. Kramer (1990) placed 

 sanddabs in the latter category; 

 however, speckled sanddabs, in par- 

 ticular, have a somewhat restricted 



bathymetric distribution as settled 

 individuals (usually found at depths 

 of 40 m and less )( Rackowski and 

 Pikitch, 1989; Kramer, 1990). Both 

 species are widely distributed as 

 pelagic larvae (as far as 724 km off- 

 shore for Pacific sanddabs and 320 

 km offshore for speckled sanddabs) 

 (Rackowski and Pikitch, 1989), but 

 settled individuals occur within a 

 somewhat more restricted coastal 

 region. 



The existence of late-stage Pacific 

 and speckled sanddabs in midwater 

 trawls conducted off central Califor- 

 nia by the National Marine Fisher- 

 ies Service (NMFS) Tiburon Labo- 

 ratory (Wyllie-Echeverria et al., 

 1990) provided an opportunity to 

 examine ontogenetic changes in dis- 

 tribution associated with metamor- 

 phosis and settlement of these two 

 sanddabs. In this paper we investi- 

 gated the vertical and horizontal 

 distribution of pelagic-stage sand- 

 dabs, with the general purpose of 

 elucidating the changes that take 

 place at metamorphosis and settle- 

 ment. Because the NMFS collec- 

 tions were made during the spring 



1 Brothers, E. B. EFS Consultants, Ithaca, 

 NY 14850. Personal commun., 1993. 



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