Copeia,

1992(l), pp. 120-128

Growth and Temperature-Induced Mortality of

Young-of-the-Year Summer Flounder (Paralichthys dentatus)

in Southern New Jersey

S. T. SZEDLMAYER, K. W. ABLE, AND R. A. ROUNTREE

From Nov. 1988 through Oct. 1989, we examined the spatial and temporal distribution, growth, and temperature-induced mortality of young-of-the-year summer flounder (Paralichthys dentatus) from Great Bay and Little Egg Harbor, Newjersey. We collected P. dentatus undergoing metamorphosis (11-15 mm TL) with plankton nets from Nov. 1988 through May 1989, as they entered the study area from adjacent continental shelf waters. Temperature-induced mortality of early postmetamorphic individuals in the laboratory was largely limited to the one instance that ambient winter temperatures dropped below 2 C (58 mortality). Mortality of a control group held in heated water (approx. 15 C) was low (3). More important, we observed recruitment of postmetamorphic larvae well after this low temperature period in Feb. In mid-June we collected by trawl, benthic young-of-the-year fish almost exclusively (98) at the mouth of two mesohaline subtidal marsh creeks. After June, young-of-the-year fish became more widespread, and we collected P. dentatus in a variety of habitats throughout the study area. In Aug. and Sept. P. dentatus were apparently able to avoid the trawl, but we collected large numbers by block nets in polyhaline subtidal marsh creeks. Young-of-the-year P. dentatus ranged 200-326 mm TL by Sept. In early Oct. 1989,we collected only two individuals by any method, and presumably most fish had migrated offshore by this time. We estimated growth rate by linear regression of TL on collection date at 1.9 mm/d from May through Sept. (n = 579, r² = 0.89). Examination of otoliths for annuli formation (n = 313, range = 126-418 mm TL) showed that the first annulus formed over a range of 275-326 mm TL. The growth rate of young-of-the-year P. dentatus in New Jersey was among the fastest for juvenile estuarine fishes. This fast growth rate and the size at first annulus formation indicate that the first mark on otoliths is indeed the first annulus, a conclusion contrary to some earlier interpretations. Thus, P. dentatus can survive New Jersey winter temperatures, grow very quickly, and attain a large size at the end of the first summer. These characteristics imply that southern New Jersey estuaries act as important nurseries for this species.

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