Increment formation in otoliths of slow-growing winter flounder (Pleuronectes americanus) larvae in cold water

Abstract

Known-age winter flounder (Pleuronectes americanus) larvae were reared in large outdoor mesocosms where the temperatures were <5°C for the first 40 days and increased slowly after this and in field enclosures where the temperature ranged between 12.3 and 19.6°C. In the cold-water group, somatic and otolith growth were suppressed at the low initial temperatures and no increments were visible. After temperatures increased, somatic growth was evident and a variable number of initial narrow increments (0.2-0.6 µm) was observed. As larvae emerged from this initial period of slow growth, they began to develop rapidly and otolith increment widths increased to 1.0-3.0 µm. In contrast, larvae reared at the warmer temperature grew rapidly and laid down daily increments beginning 5 days after hatching.