Abstract. -Patterns of otolith 

 microstructure and microchemistry 

 (Sr/Ca ratios) are described in lar- 

 val and juvenile Dover sole and re- 

 lated to developmental events and 

 habitat. The initiation of metamor- 

 phosis is associated with a transi- 

 tion from clear (protein rich) to 

 opaque (protein poor) material and 

 formation of the first accessory pri- 

 mordium. Settlement is associated 

 with the point at which growth from 

 accessory primordia completely en- 

 closes growth from the central pri- 

 mordium and Sr/Ca ratio is mini- 

 mal. No discrete otolith landmarks 

 coincide with termination of meta- 

 morphosis. 



Contrary to other flatfish that 

 have a more abrupt metamorphosis, 

 accessory primordia do not form un- 

 til the left eye traverses the mid- 

 dorsal ridge of the cranium in Do- 

 ver sole, an event that may occur 

 months after the eye first reaches 

 that position. A period of 70 days or 

 more can separate the first- and last- 

 formed accessory primordia in Do- 

 ver sole, suggesting that all acces- 

 sory primordia do not form in 

 response to a single event. 



A relationship between increments 

 and days is validated for Stage 3-5 

 metamorphic and post-metamorphic 

 stages. Duration of Stages 3 and 4 

 was in close agreement with predic- 

 tions based on seasonal distribu- 

 tions. Duration of Stages 1 and 2, 

 as determined by unvalidated incre- 

 ment counts, was about half as long 

 as determined from seasonal distri- 

 butions. 



Relationships between otolith 

 microstructure, microchemistry, and 

 early life history events in Dover 

 sole, M/crostomus pac/ficus 



Christopher L. Toole 



Department of Fisheries and Wildlife 



1 04 Nash Hall, Oregon State University 



Corvallis, OR 9733 1 -3803 



Present address: Environmental and Technical Services Division 



National Marine Fisheries Service 



91 I NE I 1th Ave., Suite 620, Portland, OR 97232 



Douglas F. Markle 

 Phillip M. Harris 



Department of Fisheries and Wildlife 

 1 04 Nash Hall, Oregon State University 

 Corvallis, OR 9733 1 -3803 



Manuscript accepted 18 May 199:!. 

 Fishery Bulletin 91:732-753 1 1993 1. 



Changes in otolith microstructure 

 often correlate, and are presumed syn- 

 chronous, with morphological and be- 

 havioral changes in larval and juve- 

 nile fish (Brothers and McFarland, 

 1981; Victor. 1982; Fowler, 1989; 

 Ozawa and Penaflor, 1990; Gartner, 

 1991). The formation of secondary 

 growth centers (accessory primordia) 

 on flatfish otoliths is associated with 

 metamorphosis in starry flounder, 

 Platichthys stellatus (Campana, 

 1984a); plaice, Pleuronectes platessa 

 (Alhossaini et al., 1989, Karakiri et 

 al., 1989); California halibut, Para- 

 lichthys californicus (Kramer, 1991); 

 and winter flounder, Pseudopleu- 

 ronectes americanus (Sogard, 1991). 

 Daily growth increments from acces- 

 sory primordia are wider and are 

 more likely composed of subdaily in- 

 crements than those from the cen- 

 tral primordium (Campana, 1984a; 

 Karakiri et al., 1989; but also see 

 Alhossaini et al., 1989). 



Metamorphosis in flatfish includes 

 a number of morphological and be- 

 havioral changes, most notably, eye 

 migration and settlement from the 

 water column to the sea floor. In most 



flatfish species, metamorphosis ap- 

 pears to be rapid; eye migration and 

 settlement occur nearly simulta- 

 neously over a period of about 1 week 

 (starry flounder, winter flounder, 

 California halibut) to 3 weeks (pla- 

 ice) (Ryland, 1966; Policansky, 1982; 

 Campana, 1984a; Chambers and 

 Leggett, 1987; Gadomski et al, 1992). 

 Although timing of accessory primor- 

 dium formation is not discussed in 

 these studies, examination of pub- 

 lished photographs suggests that the 

 oldest and most recent accessory pri- 

 mordia are separated by only a few 

 daily growth increments. In plaice, 

 the earliest-formed accessory primor- 

 dium (Alhossaini et al., 1989) or an 

 unspecified accessory primordium 

 (Karakiri et al., 1989) have been in- 

 terpreted as settlement marks. In 

 winter flounder, the earliest-formed 

 accessory primordium has been in- 

 terpreted as the point from which 

 post-metamorphic age of an indi- 

 vidual is determined (Sogard and 

 Able, 1992). Counts and measure- 

 ments of growth increments from 

 accessory primordia to the otolith 

 edge have been used to infer settle- 



732 



