Reference |
Niva, T. & M. Julkunen. 1998. Effect of population fluctuation of vendace (Coregonus albula) on the diet and growth of stocked brown trout (Salmo trutta). Arch. Hydrobiol. Spec. Issues Advanc. Limnol. 50:295-303. |
Abstract |
In 1991, a strong year-class of vendace (Coregonus albula) was born in an oligotropic Lake Iso-Porontima (3.45 km2), northeastern Finland. The fish of the year-class grew slowly: after the first summer, the mean wet body mass of 2.0 g was reached and after the third summer 6.9 g. The year-class 1991 dominated the vendace population until 1994. Juvenile brown trout (Salmo trutta) were stocked annually to the lake (6 fish per hectare in 1991-1994). In 1991, the brown trout fed predominantly on vendace and the average wet body mass of vendace in the stomachs was 1.2 g. In 1992, 1993, and 1994 proportion of vendace in the diet decreased as the mean wet body mass of vendace increased. While the annual proportion of vendace in the diet decreased, the proportion of nine-spined stickleback (Pungitius pungitius) in the diet of brown trout increased. The mean wet body mass of nine-spined stickleback in the stomachs was 0.2-0.4 g in 1991-1994. The diet shifted from vendace to nine-spined stickleback was consequently affected by the increase in the mean size of vendace of the year-class 1991 and by the lack of strong vendace year-classes in 1992-1994. The diet shift decreased the growth rate of brown trout in 1993. In spite of the predation pressure by brown trout, the year-class 1991 of vendace resulted in a total catch of 15 kg per hectare, predominantly in 1993. This indicates that the growth pattern of vendace population was not predator-induced, suggesting a ‘bottom-up’ control between the trophic levels. |
Tag |
Coded Wire Tag (CWT) Visible Implant Elastomer (VIE) |
Objective |
Evaluate stocking programs |
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