526 



Fishery Bulletin 93(3), 1995 



0.3 

 0.2 

 0.1 

 

 -0.1 

 -0.2 

 i -0.3 



ing to stage 3 to those corre- 

 sponding to stage 5 takes ap- 

 proximately five weeks. 



Morphological changes associ- 

 ated with metamorphosis prob- 

 ably decrease the buoyancy of 

 pelagic sanddabs. Laroche et al. 

 (1982) found an increase in 

 otolith growth relative to growth 

 in length at metamorphosis for 

 Parophrys vetulus, which was 

 similar to that observed for the 

 two sanddab species in this study 

 and for Rhombosolea tapirina 

 (Jenkins, 1987). Reared Paro- 

 phrys vetulus that were close to 

 settlement frequently rested on 

 their sides on the bottom and 

 swam with their bodies at an angle 

 (Laroche et al., 1982). This behav- 

 ior may be related to decreased 

 buoyancy as a result of the ossifi- 

 cation of bony structures and to the 

 large increase in otolith size 

 (Laroche et al., 1982). In addition, 

 the gas bladder is lost during meta- 

 morphosis in some species of flat- 

 fish, including the related Atlan- 

 tic species Citharichthys arctifrons (Richardson and 

 Joseph, 1973; Ahlstrom et al., 1984). Laidig 2 observed 

 that the gas bladder was reduced in stage-4 Pacific 

 sanddabs and absent in 90% of stage-5 specimens. 



Upwelled 

 Non-upwelled 



Mid-depth 



Stage 2 Stage 3 Stage 4 



Stage 3 Stage 4 Stage 5 



Stage 5 Stage 2 



Figure 10 



Mean standard scores and standard errors of metamorphic stages of Pacific and 

 speckled sanddabs, Citharichthys sordidus and C. stigmaeus, collected in shallow 

 and mid-depth trawls during 1990 and 1991 in upwelling and non-upwelling areas 

 (upwelling=surface salinity >33.6 ppt and surface temperature <11°C). 



2 Laidig, T. E. Tiburon Laboratory, Southwest Fish. Sci. Cent., 

 Natl. Mar. Fish. Serv., NOAA, 3150 Paradise Drive, Tiburon, 

 CA 94920. Personal commun., 1994. 



