Swim fitness of European eel (Anguilla anguilia)

Palstra, A. and Székely, Csaba and Ginneken, V. van and Thillart, G. van den (2005) Swim fitness of European eel (Anguilla anguilia). In: Society for Experimental Biology Annual Main Meeting, 2005. július 11-15., Barcelona, Spanyolország.

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Abstract

European silver eels migrate 5500-km to their assumed spawning grounds in the Sargasso Sea. We found that eels swim 4–6 times more efficient than non eel-like fish and utilise ca. 60 g fat per kg for migration. In order to be able to compare the performance of eels from different locations and under different conditions we developed a swim fitness test. Swim trials with 162 female eels weighing 200–1500 g were performed in 22 Blazka-type swimtunnels in a climatised room at 18 -C with running fresh or salt water. Speed and endurance swim trials started at 0.5 up to 1 meter per second (m/s) with increments of 0.1 m/s. Eels reached maximum aerobic swim speeds of 1.64 body-length per second (BL/s). Although they did not swim fast, they swam almost equally efficient at all speeds between 0.5 and 1.5 BL/s. Both maximum and optimum swim speeds were found lower in silver eels than in yellow eels. Absolute performance in m/s and cost of transport were similar since silver eels were bigger. A single day swim test was developed to discriminate between good and poor swimmers. For the infection with the swim-bladder parasite Anguillicola crassus, a negative correlation was found between infection pressure and optimum swim speeds. A positive correlation was found between bladder damage and cost of transport. Thus it is clear that the swim-bladder parasite reduces the capacity for long distance migration to the Sargasso Sea.

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