Laboratory experiments were conducted on juvenile summer flounder Paralichthys dentatus (41 to 80 mm total length) to determine low temperature tolerance (2 to 3 "C) a t 10, 20, and 30 %salinity, and to measure feeding rate, assimilation efficiency, growth rate and growth efficiency at 2, 6, 10. 14, 18 "C and 10, 20 and 30 '7' salinity. There was 100 % sunival at temperatures above 3 'C, suggesting that juvenile summer flounder are able to survive most winter water temperatures encountered in north/central Mid-Atlantic Bight (MAB) estuaries. Mortality was 42 % after 16 d at 2 to 3 'C, and was highest in fish < 50 mm TL (1 g). Mean specific growth rates were not significantly different between 2 and 10 "C (mean = 0.14 % d-'), and these rates were not significantly different from zero. Mean growth rate increased to 2.4 "0 d-' at 14 ' C and 3.8 O/ O d-' at 18 OC. Ad libitum feeding rate showed a similar relationship to temperature. Mean assimilation efficiency (60.1 %) was not affected by temperature. Mean growth efficiency ( K , ) was significantly lower at 6 "C (-23.1 "h) than a t 14 and 18 "C (18.4 and 22.1 %, respectively), and was highly variable. Salinity had no significant effect on any parameters measured, suggesting that factors other than salinity are controlling spatial distributions. Mortality resulting from acute exposure to low temperature probably occurs during one 2 to 4 wk period each winter Recruitment success from north/central MAB estuaries may be lower in years with late winter cold periods (i.e. March vs December) due to increased numbers of fish being exposed to lethal low temperatures. Additional mortahty probably results from low growth rates caused by sub-optimal temperatures (i.e. < 10 "C) throughout the spring. The annual contribution of new recruits from northern estuanes appears to b e dependent on winter temperature regime, particularly on the magnitude and timing of temperature minima.
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Malloy et al. (1991) studied this question.