Food, Growth and Biological Production of European Eel Anguilla anguilla in a Small Stream in Jutland, Denmark

Yellow eels were sampled by electrofishing in 1979, 1980 and 1981 in Vester Vedsted Baeck, Denmark, stem 6 km, catchment 24 km2, with outlet to the North Sea. Yellow eels were aged by burning the otoliths. The eels were not sexed, and they varied from 6.5 to 44 cm in length. The ages varied from 0+ to 10+ year. The annual growth rate ∆ varied from 3.4 cm for 0+ eel to 2.2 cm for 10+ eel with a mean of 3.1 cm. Body mass wet wt. was recalculated to Kcal energy, with an annual growth rate ∆ of 5.33 Kcal. In contrast to body mass, the annual growth rate ∆ in Kcal increased with age. Von Bertalanffy growth trajectory (cm) of length-at-age was calculated and L∞ = 118.4 cm. Annual natural mortality M was estimated, and M was significantly depending on body mass, i.e. high M and low body mass vs. low M at high body mass. The biological production was calculated to 13.5 g wet weight m-2 year-1. Total 780 eel stomachs were analyzed, of which 287 (37%) were empty. The weight of food content (2.1% of eel body mass) increased proportional with eel body mass. Chironomid larvae, Ephemeroptera nymph, Simulium larvae and Gammarus pulix were the dominating food taxa, followed by Trichoptera larvae. Size of prey were independent on length of eel.