Scaling relationships, individual variation and the influence of temperature on maximum swimming speed in early settled stages of the turbot Scophthalmus maximus

Abstract

Escape-swimming speeds (U max) were studied in settled turbot (Scophthalmus maximus L.) reared at 18°C. Metamorphosis was complete at 4.0 cm total length (TL). U max scaled in proportion to TL0.74 in fish of 0.88 5o 8.00 cm TL at 18▿C. The scaling relationship for U max was similar for temperatures between 13 and 23°C and could be fitted by the model: $$U_{\max } = 28.4 + 10.9\left( {\frac{{temp - 13}}{5}} \right) + 10.3{\text{ }}TL$$ . U max temperature-dependent, with a Q10 of 1.77 over the temperature range studied. Analysis of covariance showed that U max for farmed turbot was 14% lower than for wild fish filmed within 2 wk of capture; 3 mo after capture the average differences in escape performance were no longer significant, which suggests that the lower escape speeds of farmed fish are due to acclimation effects and not genetic stock differences. In order to assess the individual variability of U max, 18 wild juvenile turbot [TL=6.2±0.4 cm (Week 1) to 7.5±0.5 cm (Week 17); means±SD] were maintained in individual containers at 18°C. U max was determined weekly for 6 wk, standardised for fish length using the scaling relationship U max=1.46 TL 0.74, and individuals were ranked in order of performance. Temperature was reduced after 6 wk to 13°C, resulting in a significant decline in U max from 104.0±14.4 to 87.8±12.5 cm s-1 (means±SD). After 3 wk at 13°C U max had increased to a level not significantly different from that at 18°C. Kendall's coefficient of concordance showed that repeatability of ranking of the experimental U max of individuals was maintained over a 13 wk period and through temperature change. The results demonstrate that escape-swimming speeds in juvenile turbot are repeatable, individually variable, and can be modified in response to temperature acclination.