Does the introduced brook trout (Salvelinus fontinalis) affect growth of the native brown trout (Salmo trutta)?
Non-native brook trout have become widely established in North European streams. We combined evidence from an artificial-stream experiment and drainage-scale field surveys to examine whether brook trout suppressed the growth of the native brown trout (age 0 to age 2). Our experimental results demonstrated that brown trout were unaffected by the presence of brook trout but that brook trout showed reduced growth in the presence of brown trout. However, the growth reduction only appeared in the experimental setting, indicating that the reduced spatial constraint of the experimental system may have forced the fish to unnaturally intense interactions. Indeed, in the field, no effect of either species on the growth of the putative competitor was detected. These results caution against uncritical acceptance of findings from small-scale experiments because they rarely scale up to more complex field situations. This and earlier work suggest that the establishment of brook trout in North European streams has taken place mainly because of the availability of unoccupied (or underutilized) niche space, rather than as a result of species trait combinations or interspecific competition per se.
KeywordsAlien species Boreal streams Interspecific competition Multiscale Salmonids
- Blanchet S, Loot G, Grenouillet G, Brosse S (2007) Competitive interactions between native and exotic salmonids: a combined field and laboratory demonstration. Ecol Freshw Fish 16:133–143Google Scholar
- Kerr SJ, Grant RE (1999) Ecological impacts of fish introductions: Evaluating the risk. Fish and Wildlife Branch, Ontario Ministry of Natural Resources, Petersborough, OntarioGoogle Scholar
- Korsu K, Huusko A, Muotka T (2008) Ecology of alien species with special reference to stream salmonids. Boreal Env Res 13(Suppl. A):43–52Google Scholar
- Nakano S, Miyasaka H, Kuhara N (1999) Terrestrial-aquatic linkages: riparian arthropod inputs alter trophic cascades in a stream food web. Ecology 80:2435–2441Google Scholar
- Ruesink JL (2005) Global analysis of factors affecting the outcome of freshwater fish introductions. Cons Biol 19:1883–1893Google Scholar
- Werner EE (1998) Ecological experiments and a research program in community ecology. In: Resetarits Jr WJ, Bernardo J (eds) Experimental ecology. Issues and perspectives. Oxford University Press, pp 3–26Google Scholar