Performance of four salmonids species in competition with Atlantic salmon Aimee Lee S. Houde a , Chris C. Wilson b , Bryan D. Neff a, ⁎ a Department of Biology, Western University, London, Ontario N6A 5B7, Canada b Aquatic Research and Monitoring Section, Ontario Ministry of Natural Resources and Forestry, Trent University, Peterborough, Ontario K9J 7B8, Canada abstract article info Article history: Received 29 May 2016 Accepted 28 October 2016 Economically and culturally important salmonid species often compete with Atlantic salmon (Salmo salar) re- leased from stocking programs or that escaped during aquaculture production. Such competitive interactions may lower the individual fitness of these species by reducing survival and body growth. Here, we exposed juve- nile brown trout (S. trutta), rainbow trout (Oncorhynchus mykiss), Chinook salmon (O. tshawytscha), and coho salmon (O. kisutch) to juvenile Atlantic salmon in artificial streams for 10 months. Survival and fitness-related traits of the four species were not negatively impacted by the presence of Atlantic salmon. The results suggest that brown trout and rainbow trout have better competitive abilities than Atlantic salmon, and that Chinook salmon and coho salmon have limited competitive interactions with Atlantic salmon. Although we discuss certain environmental conditions that can favor Atlantic salmon as a competitor at the juvenile life stage, Atlantic salmon may have little impact on the productivity of these four species. © 2017 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved. Keywords: Ecological niche overlap Aggression Stocking Aquaculture Survival Growth Introduction Salmonids, such as Pacific salmon (Oncorhynchus sp.), Atlantic salm- on (Salmo salar), rainbow trout (O. mykiss), and brown trout (S. trutta), have been intentionally introduced globally to provide fisheries, con- tributing millions of dollars to local economies (Crawford and Muir, 2008; Gozlan et al., 2010). Salmonid aquaculture has also been expanding globally and may be a source of unintentional introductions of salmonids into foreign locations (Naylor et al., 2000; Bostock et al., 2010). The intentional and unintentional introductions of salmonids have inadvertently created the potential for interspecific competition with native salmonids (Crawford, 2001). On one hand, this interspecific competition may limit the production of these intentionally introduced salmonids (Gozlan et al., 2010). On the other hand, interspecific compe- tition may negatively impact the production of culturally or economi- cally important native salmonid populations (Hearn, 1987; Fausch, 1988). A better understanding of interspecific competition among sal- monids is therefore relevant for both supporting local economies and conserving native biodiversity (Simberloff and Stiling, 1996; Gozlan et al., 2010). Interspecific competition is typically greater between species with higher ecological niche overlap than those with lower overlap (Hutchinson, 1957; Maskell et al., 2006). Salmonids are territorial at ju- venile life stages and tend to compete for similar resources in nursery streams (Kalleberg, 1958; Gibson, 1981; Scott et al., 2005b), but there are differences in the degree of niche overlap between species (e.g. Gibson, 1981; Heland and Beall, 1997). Competing individuals may re- duce niche overlap by utilizing sub-optimal habitats (MacArthur and Levins, 1967; Berg et al., 2014; Houde et al., 2016), which may reduce survival and growth (Hearn and Kynard, 1986). Species that are more aggressive may be more likely to secure optimal resources than those that are less aggressive (Holway and Suarez, 1999). Overall, the extent of interspecific competition between salmonid species pairs should co- vary with both the degree of niche overlap and interspecific differences in aggressive behaviour. Concerns have been expressed that Atlantic salmon may negatively impact the production of culturally important native salmonids on the West Coast of North American where escapes from aquaculture net pens sometimes occur (Naylor et al., 2000; Bostock et al., 2010). Wild reproduction and population establishment from aquaculture escapes have been identified as a potential threat to native populations of Pacific salmon such as Chinook salmon (O. tshawytscha), coho salmon (O. kisutch), and rainbow trout, among others (Volpe et al., 2001; Piccolo and Orlikowska, 2012; Fisher et al., 2014). As these species sup- port significant fisheries and are the focus of conservation efforts on the West Coast (Willson and Halpuka, 1995), potential ecological effects from aquaculture escapes and establishment of Atlantic salmon are a significant concern (Piccolo and Orlikowska, 2012; Fisher et al., 2014). Each of these species as well as brown trout were historically introduced into the Laurentian Great Lakes and became naturalized (Crawford, 2001; Stanfield et al., 2006). Ironically, rehabilitative stocking of Atlantic salmon in Lake Ontario, where it was historically native (Crawford, 2001), has been identified as a potential concern for affecting the pro- duction of these naturalized introduced salmonids that support eco- nomically important fisheries (Dietrich et al., 2008), which has been Journal of Great Lakes Research 43 (2017) 211–215 ⁎ Corresponding author. E-mail address: bneff@uwo.ca (B.D. Neff). http://dx.doi.org/10.1016/j.jglr.2016.10.017 0380-1330/© 2017 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Journal of Great Lakes Research journal homepage: www.elsevier.com/locate/jglr