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Turkish Journal of Zoology

DOI

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Abstract

Seasonal changes in sea temperature levels affect the swimming performance of fish. This study investigates if a change of 5°C from 7 to 12°C in water temperature has a significant effect on the maximum swimming performance of whiting, Merlangius merlangus, which is one of the most common species caught in the bottom trawl fisheries of the North Sea. The effect of this seasonal change on swimming performance was shown by two experiments. A temperature increase from 7°C to 12°C was shown to cause a decrease in the minimum twitch contraction time of the lateral muscle, when stimulated by an electric pulse, from 45.8ms to 33.9ms. This gives a maximum tail beat frequency of 10.9Hz at 7°C rising to 14.7Hz at 12°C. In the second set of experiments, the escape response of fish to sound stimuli at these two temperatures was investigated. The Mauthner Escape Reflexes of the fish were found to be significantly slower at 7°C than at 12°C. Mean escape latency at 12°C (27.6) was significantly shorter than that at 7°C (34.8) (t test, P< 0.001). The mean value of the time taken to complete stage 1 at 12°C (45.6ms) was significantly faster than that at 7°C (57.7ms) (t test, P< 0.001). Similarly, the mean value of the time taken to complete stage 2 at 12°C (119.9ms) was significantly faster than that at 7°C (154.3ms) (t test, P< 0.05). The general underlying physiological effect of a temperature increase of 10°C was to almost double the speed of fish maximum swimming ability (Q_{10°C} =1.81). The results of these experiments have shown that, due to low water temperature, the maximum swimming speed of whiting in late winter and spring is lower than that in late summer and autumn.

Keywords

Merlangius merlangus, temperature effect, muscle contraction, escape speed.

First Page

255

Last Page

262

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