INCREMENT FORMATION IN OTOLITHS OF SLOW-GROWING WINTER FLOUNDER (PLEURONECTES-AMERICANUS) LARVAE IN COLD-WATER

Known-age winter flounder (Pleuronectes americanus) larvae were reared in large outdoor mesocosms where the temperatures were <5 degrees C f or the first 40 days and increased slowly after this and in field encl osures where the temperature ranged between 12.3 and 19.6 degrees C. I n the cold-water group, somatic and otolith growth were suppressed at the low initial temperatures and no increments were visible. After tem peratures increased, somatic growth was evident and a variable number of initial narrow increments (0.2-0.6 mu m) was observed. As larvae em erged from this initial period of slow growth, they began to develop r apidly and otolith increment widths increased to 1.0-3.0 mu m. In cont rast, larvae reared at the warmer temperature grew rapidly and laid do wn daily increments beginning 5 days after hatching.