Growth of winter flounder ( Pseudopleuronectes americanus) and smooth flounder ( Liopsetta putnami) in heated and unheated water

Abstract

0-group and I-group winter ( Pseudopleuronectes americanus) and smooth ( Liopsetta putnami) flounder were reared at the Jackson Estuarine Laboratory, Durham, NH, U.S.A., between November 1975 and June 1976. Both species gained weight approximately three times more rapidly in heated than in unheated water. In unheated water the smallest winter flounder gained, on average, 116% of their body weight per month. Larger 0-group winter flounder increased body weight by 55% per month, while comparably sized female and male smooth flounder gained 52% and 28% per month, respectively. I-group female smooth flounder gained 9.5% and male smooth flounder 8.5% per month in heated water. In unheated water increases were 13%, 22%, and 14% per month for 0-group winter, female smooth, and male smooth flounder, respectively. I-group winter flounder in unheated water gained weight twice as rapidly (9.5% per month) as I-group female and male smooth flounder (4.0% and 4.5% per month, respectively). Fish were fed a moist diet at a level of 10% of their body weight per day. Conversions (dry weight of food/wet weight of fish) ranged from 1:1 for 0-group winter flounder in heated water to 27:1 for I-group smooth flounder in unheated water. Disease was a major cause of mortality. Vibrio anguillarum was confirmed as a pathogen; myxobacteria, and the protozoan parasites Kudoa sp. and Nosema sp. were associated with losses.