INTERPRETATION OF OTOLITH MICROSTRUCTURE IN JUVENILE WINTER FLOUNDER (PSEUDOPLEURONECTES-AMERICANUS) - ONTOGENIC DEVELOPMENT, DAILY INCREMENT VALIDATION, AND SOMATIC GROWTH RELATIONSHIPS

In winter flounder (Pseudopleuronectes americanus), sagittae developed secondary origins of calcium carbonate deposition during metamorphosis just prior to completion of eye migration. Sagittae and lapilli of larvae were bilaterally symmetrical, but those of postmetamorphic individuals showed increasing morphological asymmetry between the left and right side. In juveniles marked with oxytetracycline and maintained in field enclosures for 10 d, increment deposition on sagittae was daily if somatic growth following marking was good (> 0.25 mm.d-1), but less than daily in individuals with poor or negative somatic growth (< 0.25 mm.d-1). Narrowly spaced increments or divergence of otolith growth from the main rostral-postrostral growth axis, where counts were made, may have limited detection of daily deposition. Lack of detectable daily increments occurred primarily in larger juveniles (> 50 mm total length), which had lower absolute growth rates than newly settled juveniles. In oxytetracycline-marked fish there was a significant correspondence between otolith growth and somatic growth in both length and weight. The strength of this relationship, which varied with the specific radius used, was highest (r = 0.854) for the rostral radius of the left sagitta; increment widths along this radius are reliable estimators of prior somatic growth rates.