Foraging behaviour in benthivorous fish

University dissertation from Department of Ecology, Lund University

Abstract: The foraging ability of an organism is essential since it affects various traits, e.g. growth, reproduction effort, social status and, ultimately, fitness. Foraging is often associated with food intake but includes more aspects such as searching for and assessing food patches and evaluating the patch as good or bad compared to the rest of the environment. On top of that, a forager also has to survive while foraging, and consequently, has to trade-off food and safety. Moreover, foragers are not always foraging alone but in groups. For individuals foraging in groups it may be a way of diluting the individual risk of predation and enhancing their information on predation risk and where to find food, but it may also lead to increased competition for resources. Hence, foraging decisions made in a food patch rely on estimations of several factors. In my thesis I have investigated the effect of resource distribution, resource density, predation risk and group size dynamics on foraging behaviour in benthivorous fish. I have used artificial food patches in all studies and measured giving-up density (GUD) of benthivorous fish in those food patches. In both pools and natural lakes I have shown that benthivorous fish are capable of assessing resources in their environment. I have found that benthivorous fish harvest and leave experimental patches at harvest rates (i.e. GUD) that correspond to both the quality of the surrounding environment and to their prior expectations of potential lifetime growth. My results also show that perceived risk of predation affect how, where and when benthivorous fish utilize resources. In my studies benthivorous fish mainly foraged in group, which may be a way to enhance information on predation risk and where to find food. Hence, patch use behaviour may be used successfully to gain insights about the ecology of benthivorous fish and ultimately to properties of different lake ecosystems (e.g. to reveal which mechanisms structure communities).

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