Rainbow trout (Oncorhynchus mykiss) habitat overlap with wild Atlantic salmon (Salmo salar) and brook trout (Salvelinus fontinalis) in natural streams: do habitat and landscape factors override competitive interactions?

Abstract

The purpose of this study was to update rainbow trout (Oncorhynchus mykiss) invasion status, delineate factors that increase the invasion probability, and quantify habitat overlap between invasive rainbow trout and native Atlantic salmon (Salmo salar) and brook trout (Salvelinus fontinalis) on Prince Edward Island, Canada. Analysis of landscape-level variables in 26 watersheds (14 with and 12 without rainbow trout) demonstrated that watershed slope, percent agricultural land use, and distance to the nearest rainbow trout population significantly increased the probability of rainbow trout establishment. Two independent reach-level fish community surveys were conducted by electrofishing in combination with habitat surveys. Reaches with rainbow trout had higher stream slope, Atlantic salmon were found in wider reaches with larger substrate, and brook trout were typically dominant in headwater reaches with finer substrate. Findings at multiple ecological scales illustrated that rainbow trout invasion success is positively influenced by the presence of high-slope habitat. Habitat separation of the three salmonid species indicates that competition with introduced rainbow trout may not be the most significant threat to native salmonid populations.

Otolith microchemistry and acoustic telemetry reveal anadromy in non-native rainbow trout (Oncorhynchus mykiss) in Prince Edward Island, Canada

“…However, we did observe short-distance movements between adjacent estuaries (>20 km), suggesting that PEI rainbow trout may act as interconnected metapopulations (Schtickzelle and Quinn 2007). Indeed, proximity to an established population of rainbow trout is an important factor influencing the probability of rainbow trout establishing in any given system on PEI (Roloson et al 2018). The species has had populations present in the area for a century (MacCrimmon 1971;Quinn et al 2001;Hendry et al 2000;Phillis et al 2016); however, a long-term, long-distance migratory strategy has apparently yet to develop.…”

“…] found in about two dozen watersheds (Cairns and MacFarlane 2015). Rainbow trout have expanded their distribution and are now found in at least 32 watersheds (Roloson et al 2018).…”

“…Once the species establishes itself, subsequent invasions occur through dispersal between interconnected freshwater watersheds and potentially to neighboring coastal watersheds where the population has access to the sea. Despite the widespread introductions, only a few instances of anadromy in rainbow trout have been reported in South America (Pascual et al 2001) and several locations in eastern Canada, including Quebec (Thibault et al 2009), Bras D'Or Lakes in Nova Scotia (Madden et al 2010), and Prince Edward Island (PEI) (Roloson et al 2018).…”

“…On PEI, Canada, over one million rainbow trout were introduced to a variety of watersheds via stocking and aquaculture escapes, and established populations were reported as early as 1971 (MacCrimmon 1971;Guignion et al 2010). As of 2018, rainbow trout had established populations in 32 rivers (Gormley et al 2005;Roloson et al 2018). Watersheds with recently established rainbow trout had source populations nearby, suggesting that anadromous movements between adjacent rivers were perpetuating invasion (Roloson et al 2018).…”

“…As of 2018, rainbow trout had established populations in 32 rivers (Gormley et al 2005;Roloson et al 2018). Watersheds with recently established rainbow trout had source populations nearby, suggesting that anadromous movements between adjacent rivers were perpetuating invasion (Roloson et al 2018). In eastern Quebec, where some populations of introduced rainbow trout have become anadromous, a genetic study reported several individuals had similar genetic signatures to rainbow trout on PEI, raising questions about the geographic scale of anadromous rainbow trout originating on PEI (Thibault et al 2009).…”