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- Brönmark, Christer, et al.
(author)
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Indirect effects of fish community structure on submerged vegetation in shallow, eutrophic lakes : an alternative mechanism
- 1992
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In: Hydrobiologia. - Dordrecht : Springer Netherlands. - 0018-8158 .- 1573-5117. ; 243/244:1, s. 293-301
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Journal article (peer-reviewed)abstract
- The loss of submerged macrophytes during eutrophication of shallow takes is a commonly observed phenomenon. The proximate reason for this decline is a reduction of available light due to increasing phytoplankton and/or epiphyton biomass. Here we argue that the ultimate cause for the transition from a macrophyte-dominated state to a phytoplankton-dominated state is a change in fish community structure. A catastrophic disturbance event (e.g. winterkill) acting selectively on piscivores, cascades down food chains, eventually reducing macrophyte growth through shading by epiphyton, an effect that is reinforced by increasing phytoplankton biomass. The transition back from the phytoplankton to the macrophyte state depends on an increase in piscivore standing stock and a reduction of planktivores. A conceptual model of these mechanisms is presented and supported by literature data and preliminary observations from a field experiment. © 1992 Kluwer Academic Publishers.
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- Pettersson, Lars B., et al.
(author)
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Trading off safety against food : state dependent habitat choice and foraging in crucian carp
- 1993
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In: Oecologia. - 0029-8549. ; 95:3, s. 353-357
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Journal article (peer-reviewed)abstract
- The influence of hunger level and predation risk on habitat choice and foraging in crucian carp, Carassius carassius, were studied in a laboratory experiment. Experiments were carried out in aquaria with or without a predator (pike, Esox lucius). Habitat use and foraging activity of three-fish foraging groups of either fed or hungry crucian carp were studied. Fish were allowed to choose between an open (risky) habitat with Tubifex worms and a habitat with dense vegetation (safe) without food. Habitat use was significantly affected by both risk of predation and hunger level. Crucian carp spent less time in the open habitat when there was a predator present and they also spent less time there when fed than when hungry. Furthermore, there was a significant interaction between risk of predation and hunger level, indicating a state-dependent trade-off between food acquisition and predator avoidance.
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