Jearld et al.: Early growth, behavior, and otolith development of Pleuronectes amencanus 



67 



. M < Wjt 



 





Figure 2 



Light microscope (A) and SEM (B) photographs of winter flounder Pleuronectes 

 americanus otoliths showing similarity of detail visible in both. Scale bars represent 

 10 p.. 



30 d and older, sagittae were 

 measured and used for increment 

 counts. 



Otoliths were measured to the 

 nearest micron (under a com- 

 pound microscope) along the 

 longest axis through the central 

 core and along the axis perpen- 

 dicular to that dimension using 

 an optical micrometer at 200- 

 lOOOx (depending on otolith 

 size). Most increment counts 

 were done on photographs at 

 1000 X. All increments visible in 

 at least two places on an otolith 

 were counted. Varying the focus 

 changed the resolution of incre- 

 ments; therefore the maximum 

 number of increments seen in a 

 series of pictures taken at 

 slightly-varying focal planes was 

 counted. Two or three separate 

 counts by two age-readers were 

 averaged. If the two readers dis- 

 agreed by more than two incre- 

 ments or the photographs were 

 considered unclear, that otolith 

 set was not used in daily growth- 

 increment calculations. Incre- 

 ments formed prior to yolksac 

 absorption were either absent or 

 difficult to resolve and were not 

 included in the total count. Based 

 on the work of Radtke & Scherer 

 (1982), a correction factor of 10 

 was added to the number of ob- 

 served increments in order to es- 

 tablish each larva's estimated age 

 in days from hatch. 



For scanning electron micros- 

 copy (SEM) viewing, some of the 

 larger ( 600-840 u along the larg- 

 est dimension) sagittae were pre- 

 pared according to the methods 

 in Radtke & Dean (1982). Light 

 microscope pictures of an otolith 

 were compared with SEM photo- 

 graphs of the same specimen 

 (Fig. 2) and counts were found 

 to be comparable. 



Behavioral observations 



Larval behavior was observed 

 from hatching through metamor- 



