Growth in length of newly metamorphosed young plaice and flounders was measured in the laboratory at different constant temperatures. The fish, varying in size from 15 to 40 mm, were kept in groups in plastic pails or perforated plastic crates suspended in large sea water tanks kept at 2° ,6°, 10° , 15° and 20°C. At the same time some fish were reared in perforated plastic crates suspended in the N.I.O.Z.-harbour at ambient sea water temperatures (9°C- 16°C) from 6 May to 6 June (1980) . All pails and crates were provided with aeration and sand on the bottom, and the fish were fed daily (slightly) excess amounts of chopped fresh musselmeat. Their total length was measured in millimeters at the start, after 14 days and after one month. Total length increased linearly with time, and the calculated growth-rate in length (dL/dt, mm per month) showed a highly significant positive correlation with water temperature. Mortality of the fish in the harbour was high, while in the laboratory many fish showed poor growth. However, when only the good growing fish are considered, the growth rate in the laboratory and in the harbour agreed very well. The relation with temperature can be bescribed as: 0 plaice: dL/dt (mm per month) = 1,3 (°C) + 1,7 flounder: dL/dt (mm per month) = 1,2 (°C) -7,2 Calculated growth rates for young plaice in the Wadden Sea with this model agree fairly well with the actually observed growth rates from monthly young plaice surveys. |
