Effects of increasing temperature on swimming activity of sardine, Sardina pilchardus, from two populations

Hamida Mbwana

On a global level, the average temperature is expected to increase between 1-4°C by the end of the 21st century due to the increase of anthropogenic activities . This could lead to physiological changes and behavioral alterations on marine species especially for small pelagic fishes (SPF) that are particularly sensitive to climate variabilities. This study tested the effects of high temperature exposure on the swimming activity of adult European pilchard, Sardina pilchardus, from two geographic populations that live under different thermal regimes, Olhão (south of Portugal) and Gulf du Lion, south of France. Fish were exposed to three temperature treatment, (16ºC, 20ºC, 24ºC) for one month. Fish swimming activities were recorded for 15 minutes by a video camera(GOPRO) placed 1m above the tanks. Three Swimming variables including the average speed, total distance travelled and exploration rates were calculated by using a free computerized video analysis software, ToxTrack. The results showed that temperature did not influence swimming activity in either population. Fish from France had similar average speeds across the three temperature treatments, and there is a tendency for fish from Olhão to show higher swimming activity at 20ºC, which decreased at 24ºC. Sardines from France had greater performance in speed with an increase in temperature compared to that of Olhao. The distance travelled by sardines and exploration rate from French population were usually higher than those from Olhão. The results suggest that increased water temperature might have the potential to directly affect this species through changes in swimming activity