SEASONAL AND ONTOGENIC CHANGES IN DISTRIBUTION AND ABUNDANCE OF SMOOTH FLOUNDER, PLEURONECTES PUTNAMI, AND WINTER FLOUNDER, PLEURONECTES-AMERICANUS, ALONG ESTUARINE DEPTH AND SALINITY GRADIENTS

The distribution and abundance of two potentially competing flatfish s pecies, smooth flounder, Pleuronectes putnami, and winter flounder, Pl euronectes americanus, were examined along salinity and depth gradient s in upper Great Bay Estuary, New Hampshire. Both species were abundan t in the estuary but exhibited differential use of habitats along both gradients. Smooth flounder were most abundant at the mesohaline, rive rine habitat, whereas winter flounder were most abundant at the polyha line, open-bay habitat. Both species exhibited a generalized up-river movement as salinity increased with the seasons. Smooth flounder showe d ontogenetic changes in distribution along the depth gradient, with s mallest individuals occupying shallowest depths. Intertidal mudflats w ere an important nursery area for young-of-the-year smooth flounder. W inter flounder showed little separation by size along the depth gradie nt, and few were found in the intertidal mudflat habitat. The potentia l for competition between these two species is lessened by their parti al segregation along the gradients examined.