Interactions between invading benthivorous fish and native whitefish in subarctic lakes

Abstract

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 Northern Europe, perch (Perca fluviatilis), a trophic generalist, and ruffe (Gymnocephalus cernuus), a benthic specialist, are expanding their distribution ranges northwards, colonising lakes inhabited by a native generalist, whitefish (Coregonus 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 August and September. 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 whitefish were largely independent of fish community structure and were governed by local variations in lake productivity. However, there was a sign of lowered condition of whitefish in invaded systems. Shallow and more productive lakes with higher food availability supported populations of native and invasive species. Our findings indicate that trophic specialisations of invasive species play a key role in determining their impacts on the systems they invade. This study focussed on early stages of invasion, and the outcome of species interactions may change following the establishment of new species. In addition, these impacts will not be uniform across the invaded landscape as lake‐specific variations in morphometry and resource availability will alter the competitive balance between native and invasive species.

Niche segregation facilitates coexistence between native and introduced fishes in a deep Patagonian lake

“…Fish introductions into freshwater constitute an important threat to the structure and functioning of ecosystems, as introduced species may interfere with the use of resources by native species, altering food web functioning, and leading to a decline in native fish populations due to predation and competition for food and habitat (Vander Zanden et al, 1999;Hayden et al, 2013). The ecological strategies of native and introduced species are important in terms of the invader's success in becoming established in the novel environment and the impact of that invasion (Marchetti et al, 2004).…”

“…The ecological strategies of native and introduced species are important in terms of the invader's success in becoming established in the novel environment and the impact of that invasion (Marchetti et al, 2004). Among introduced species, generalists are more likely to become successfully established (Clavel et al, 2010), since an introduced generalist may be able to use a variety of resources in the invaded habitat, thus alleviating direct competition with native taxa (Hayden et al, 2013). Conversely, an introduced specialist may be able to dominate its preferred resource and exclude native competitors (Bøhn et al, 2008).…”

Can fish introductions alter nutrient cycles in previously fishless high-latitude lakes?

“…While some studies exist on the food web changes induced by introduced fish in Fennoscandia (Bøhn and Amundsen, 2001;Hayden et al, 2013), none have focused on the consequences on nutrient cycling. Palaeolimnological analyses (i.e.…”

Visual pigments of Arctic charr (Salvelinus alpinus (L.)) and whitefish (Coregonus lavaretus (L.)) morphs in subarctic lakes

“…Population genetic studies indicate reproductive isolation among sympatric morphs of both species (Westgaard et al, 2004;Østbye et al, 2006;Praebel et al, 2013), suggesting adaptive radiation and incipient ecological speciation as a mechanisms behind their divergence. Besides the general pattern of divergence in polymorphic fish populations along the littoral-pelagic resource axis, both Arctic charr and whitefish may also diverge into the third principal niche available in subarctic lakes, the profundal habitat (Kahilainen & Østbye, 2006;Knudsen et al, 2006).…”

“…Whitefish in Lake Muddusjärvi have ecomorphologically and genetically diverged into three specialized morphs (Harrod et al, 2010;Couton, 2012). The number of gill rakers is a heritable trait in whitefish and correlated with niche utilization (Kahilainen et al, 2011;Praebel et al, 2013). The morphs are named according to body size and gill raker traits: the small sparsely rakered (SSR) whitefish is a profundal dwelling morph with the lowest number of gill rakers, the large sparsely rakered (LSR) whitefish a littoral morph having intermediate numbers of gill rakers and the densely rakered whitefish (DR) is a small sized pelagic morph with the highest number of gill rakers (Kahilainen & Østbye, 2006;Kahilainen et al, 2011).…”