The interaction of temperature and salinity on growth and food conversion in juvenile turbot (Scophthalmus maximus)

The effects of temperature and salinity on growth and feed conversion of juvenile turbot (initial mean weight 14 g) were investigated by rearing fish at (mean +/- SD) 10 +/- 0.2 degreesC, 14 +/- 0.2 degreesC, 18 +/- 0.3 degreesC and 22 +/- 0.2 degreesC and 15 +/- 0.4 parts per thousand, 15 +/- 0.4 parts per thousand and 33.5 +/- 0.1 parts per thousand for 3 months. Growth, food consumption, and food conversion efficiency were highest at 15 parts per thousand, and lowest at 33.5 parts per thousand. There was an interactive effect of temperature and salinity at the two highest temperatures (18 degreesC and 22 degreesC) but not at 10 degreesC and 14 degreesC. The optimal temperature for growth (T-opt. G) varied with salinity: T-opt. G. at 33.5 parts per thousand was 19.6 +/- 0.3 degreesC(+/- SEM), whereas the T-opt. G. at 15 parts per thousand was 22.9 +/- 1.0 degreesC, and at 25 parts per thousand was 24.7 +/- 2.1 degreesC. A similar trend was found for food conversion efficiency (FCE). The optimal temperatures for FCE were 17.4 +/- 0.5 degreesC, 17.9 +/- 1.0 degreesC and 19.0 +/- 0.9 degreesC at 33.5 parts per thousand, 25 parts per thousand and 15 parts per thousand, respectively. Overall, we found the optimal temperature-salinity combination for growth to be 21.8 +/- 0.9 degreesC and 18.5 +/- 0.8 parts per thousand. The optimal temperature-salinity combination for food conversion efficiency was found to be 18.3 +/- 0.6 degreesC and 19.0 +/- 1.0 parts per thousand. It is concluded that growth and food conversion efficiency of juvenile turbot can be improved by rearing them at intermediate salinities in the upper temperature range. (C) 2001 Elsevier Science B.V. All rights reserved.