Burst‐Swimming Performance of Larval Zebra Danios and the Effects of Diel Temperature Fluctuations

Abstract

Zebra danios Danio [Brachydanio] rerio were spawned and their eggs and larvae were reared in a simulated natural thermal regime, increasing from 21 to 30°C for 7 h and decreasing to 21°C for 17 h, daily. Burst‐swimming performance was provoked by electrical stimulation of larvae (mean total length = 3.6 mm). Responses were filmed at 400 frames/s at temperature intervals of 3°C. Distance travelled in a specified time (St), maximum velocity, and maximum acceleration increased with temperature. Size‐specific maximum velocity was considerably higher than previously reported for larvae. A predictive model relating St to temperature was developed. In theory, the observed effects of temperature could have been due to changes in physiological rates or in water viscosity, but Reynolds numbers were too high for a substantial viscosity effect. The Q10 for St was 1.6, that for maximum velocity was 1.4. Results suggest that, other factors being equal, larvae are potentially more vulnerable to predation at sunrise or at other times when water temperature is low.