Interactions between invading benthivorous fish and native whitefish in subarctic lakes

• Published in: Freshwater Biology
• Main Authors: Hayden, Brian, Holopainen, Tiina, Amundsen, Per‐Arne, Eloranta, Antti P., Knudsen, Rune, Præbel, Kim, Kahilainen, Kimmo K.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2013
• Subjects: Aquatic Science; Subarctic
• Online Access: http://dx.doi.org/10.1111/fwb.12123; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Ffwb.12123; https://onlinelibrary.wiley.com/doi/pdf/10.1111/fwb.12123

Summary Many species are expanding their distribution towards higher latitudes and altitudes in response to climate change. These range shifts are expected to change fish community structure and alter food‐web dynamics in subarctic lakes. However, the impacts of invading species on native fish and invertebrate prey communities remain understudied. The trophic ecology of invasive species determines the likelihood of direct resource competition with native taxa. In N orthern E urope, perch ( P erca fluviatilis ), a trophic generalist, and ruffe ( G ymnocephalus cernuus ), a benthic specialist, are expanding their distribution ranges northwards, colonising lakes inhabited by a native generalist, whitefish ( C oregonus lavaretus ). We predicted that increased fish diversity and density would deplete the invertebrate community and increase resource competition between native and invasive species. To assess the degree of resource competition between native and invasive species, we compared (i) fish and invertebrate community structure; (ii) diet and stable carbon and nitrogen ratios of whitefish, ruffe and perch and (iii) growth, condition and relative population size of whitefish in two non‐invaded lakes with two lakes containing one and two lakes containing both invasive species. Each lake was sampled on a single occasion between A ugust and S eptember. Benthic macroinvertebrate density and community structure were unaffected by increased consumer diversity, while top‐down control of pelagic zooplankton density and size was evident in lakes with increased fish diversity. Differences in diet and stable isotope ratios were evident between all whitefish populations, although these were not directly related to the presence of invasive species. Specialised adaptations of invasive species may confer a competitive advantage in invaded lakes; ruffe dominated the profundal niche, while perch displayed an ontogenetic shift to piscivory, reducing niche overlap with native whitefish. Growth rate and population density of ...