750 



Fishery Bulletin 91 (4), 1993 



Table 6 



Summary oflarval and juvenile Dover sole. Microstomias pacificus, metamorphic stages (as described in text and Markle et al., 1992) 

 structural landmarks on otoliths, chemical landmarks on otoliths, and habitat. 



least 70 days in some individuals. The termination 

 event of metamorphosis, as defined by Markle et al. 

 (1992), is not associated with discrete structural or 

 chemical signals. 



We propose that the landmark most likely to corre- 

 spond with the behavioral change of settlement from 

 water column to benthos is enclosure of growth from 

 the central primordium by growth from accessory pri- 

 mordia. In some individuals a minimal Sr/Ca value 

 near 0.002 may also signal this event. This behav- 

 ioral change is not instantaneous, because both Stage- 

 3 and Stage-4 larvae were collected in midwater 

 trawls. Markle et al. (1992) characterized settlement 

 in Dover sole as a gradual process in which larvae 

 make their way from an initial deep-water landing 

 zone to a shallower nursery area. Enclosure of growth 

 from the central primordium occurs near the begin- 

 ning of Stage 3, when Dover sole larvae are first col- 

 lected on the bottom in significant numbers. Thus, it 

 is reasonable to expect that this is the point at which 

 they first begin to spend a significant amount of time 

 on the bottom. 



Chronology of metamorphosis 



Periodicity of increments emanating from the central 

 primordium has not been validated, so assignment of 

 dates to otolith landmarks formed during Stage 1 and 

 Stage 2 can only be speculative. However, if incre- 

 ments are deposited approximately daily, then Stage-1 

 larvae reached a length of 20-30 mm in approximately 

 2-3 months, some Stage-1 larvae reached 46-50 mm 

 in approximately 5-8 months, and most larvae reached 

 the end of Stage 2 or beginning of Stage 3 about a year 

 after increments first formed. These rates are approxi- 

 mately double those determined from seasonal collec- 

 tions of Dover sole larvae (Markle et al., 1992). Reso- 

 lution of this discrepency must await validation of 

 increment periodicity in premetamorphic larval otoliths. 

 Periodicity of growth increments was confirmed for 

 Stage-3 and Stage-4 larvae and Stage-5 juveniles. In 

 general, duration of these stages is in agreement with 

 other studies. The duration of Stage 3 following enclo- 

 sure averaged 28 days, although it extended at least 

 65 days for one individual. Because enclosure may oc- 



