Variability in the functional role of Arctic charr Salvelinus alpinus as it relates to lake ecosystem characteristics
This study investigated how dietary habits vary with lake characteristics in a fish species that exhibits extensive morphological and ecological variability, the Arctic charr Salvelinus alpinus. Iceland is a hotspot of geological activity, so its freshwater ecosystems vary greatly in physical and chemical attributes. Associations of dietary items within guts of charr were used to form prey categories that reflect habitat-specific feeding behavior. Six prey categories were defined and dominated by snails (Radix peregra), fish (Gasterosteus aculeatus), tadpole shrimp (Lepidurus arcticus), chironomid pupae, pea clam (Pisidium spp.), and the cladoceran Bosmina sp.. These reflected different combinations of feeding in littoral stone, offshore benthic, and limnetic habitats. Certain habitat-specific feeding strategies consistently occurred alongside each other within lakes. For example, zooplanktivory occurred in the same lakes as consumption from offshore habitats; piscivory occurred in the same lakes as consumption from littoral benthic habitats. Redundancy analyses (RDA) were used to investigate how lake environment was related to consumption of different prey categories. The RDA indicated that piscivory exhibited by Arctic charr was reduced where brown trout were abundant and lakes were shallow, greater zooplanktivory occurred at lower latitudes and under decreased nutrient but higher silicon dioxide concentrations, and benthic resource consumption was associated with shallower lakes and higher altitudes. This study showed that trends previously observed across fish species were supported at the intraspecific level, indicating that a single species with flexible dietary habits can fill functional roles expected of multiple species in more diverse food webs.
KeywordsPrey habitat Diet Lake ecosystem Piscivory Zooplanktivory Consumer
This research has been supported by the European Marie Curie Research Training Network Fish ACE (Fisheries-induced Adaptive Changes in Exploited Stocks), funded through the European Community’s Sixth Framework Programme (Contract MRTN-CT-2004-005578), and a research grant provided by the Icelandic Centre for Research and the University of Washington Graduate School Fund for Excellence and Innovation. The ESIL project was funded with grants from the Icelandic Research Council, the Ministry of the Environment, the Ministry of Agriculture, and the Icelandic Fisheries Research Fund. Special thanks are given to those who participated in the Ecological Survey of Icelandic lakes, especially the Icelandic Institute of Freshwater Fisheries. We also thank Thomas Quinn, Daniel Schindler, Ulf Dieckmann, Åke Brännström, and 3 anonymous reviewers for discussing and reviewing earlier versions of this study.
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