Comparison of competitive ability between native and introduced salmonids: evidence from pairwise contests

Hasegawa, Kou; Yamamoto, Toshiaki; Murakami, Masashi; Maekawa, Koji

doi:10.1007/s10228-004-0214-x

Cited by 55 publications

(48 citation statements)

References 26 publications

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“…In addition, Kawaguchi et al (2003) showed that excluding terrestrial prey, as rainbow trout do, caused Dolly Varden to emigrate. Regardless of the combination of mechanisms, the problem is likely to be widespread because rainbow trout are rapidly invading other Hokkaido streams (Takami and Aoyama 1999) and have been reported to displace Dolly Varden as well as other native salmonids such as white-spotted charr (Salvelinus leucomaenis), Sakhalin taimen (Hucho perryi), and masu salmon (O. masou; Hasegawa et al 2004;Kitano 2004;Morita et al 2004).…”

Section: Discussionmentioning

confidence: 99%

Invading rainbow trout usurp a terrestrial prey subsidy from native charr and reduce their growth and abundance

et al. 2007

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Movements of prey organisms across ecosystem boundaries often subsidize consumer populations in adjacent habitats. Human disturbances such as habitat degradation or non-native species invasions may alter the characteristics or fate of these prey subsidies, but few studies have measured the direct effects of this disruption on the growth and local abundance of predators in recipient habitats. Here we present evidence, obtained from a combined experimental and comparative study in northern Japan, that an invading stream fish usurped the flux of allochthonous prey to a native fish, consequently altering the diet and reducing the growth and abundance of the native species. A large-scale field experiment showed that excluding terrestrial invertebrates that fell into the stream with a mesh greenhouse reduced terrestrial prey in diets of native Dolly Varden charr (Salvelinus malma) by 46-70%, and reduced their growth by 25% over six weeks. However, when nonnative rainbow trout (Oncorhynchus mykiss) were introduced, they monopolized these prey and caused an even greater reduction of terrestrial prey in charr diets of 82-93%, and reduced charr growth by 31% over the same period. Adding both greenhouse and rainbow trout treatments together produced similar results to adding either alone. Results from a comparative field study of six other stream sites in the region corroborated the experimental findings, showing that at invaded sites rainbow trout usurped the terrestrial prey subsidy, causing a more than 75% decrease in the biomass of terrestrial invertebrates in Dolly Varden diets and forcing them to shift their foraging to insects on the stream bottom. Moreover, at sites with even low densities of rainbow trout, biomass of Dolly Varden was more than 75% lower than at sites without rainbow trout. Disruption of resource fluxes between habitats may be a common, but unidentified, consequence of invasions, and an additional mechanism contributing to the loss of native species.

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Section: Discussionmentioning

confidence: 99%

Invading rainbow trout usurp a terrestrial prey subsidy from native charr and reduce their growth and abundance

et al. 2007

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“…data). Interspecific competition [23,24], predation [25] and redd superimposition [26] could be mechanisms responsible for the displacement of white-spotted charr by brown trout, because larger pools with good water visibility generally provide an increased opportunity for direct contact among individuals. Further detailed field and experimental studies are needed to elucidate the mechanisms responsible for the displacement of native salmonid fishes, and to allow the implementation of control measures for harmful exotic salmonid fishes.…”

Section: Resultsmentioning

confidence: 99%

Differences in longitudinal distribution patterns along a Honshu stream of brown trout Salmo trutta, white-spotted charr Salvelinus leucomaenis and masu salmon Oncorhynchus masou

et al. 2010

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Brown trout Salmo trutta were first introduced into Japan in 1892, and they currently naturally reproduce in several rivers in Honshu and Hokkaido, Japan. Although negative impacts of brown trout introductions on native salmonid fishes have been documented in some Hokkaido rivers, studies of ecological interactions between brown trout and native salmonid fishes on Honshu are limited. In this study, we describe the longitudinal distribution patterns of introduced brown trout, white-spotted charr Salvelinus leucomaenis and masu salmon Oncorhynchus masou in a 4 km stretch of a stream in central Honshu. Underwater observations were conducted in all pools within upstream, middle and downstream sections (190-400 m in length) of this stretch in order to estimate the densities of these species. Only white-spotted charr was observed in the upstream section, while brown trout and masu salmon were observed in the middle and downstream sections. Masu salmon densities, however, were much lower than brown trout densities. In the downstream section, white-spotted charr was absent. These results are consistent with results from previous studies of Hokkaido rivers, where it was found that white-spotted charr in low-gradient areas tend to be displaced by brown trout.

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“…The rainbow trout also tend to become larger than the masu salmon. A large body size is an advantage in interference interspecific competition among salmonid species [32], although the competitive abilities of the rainbow trout and the masu salmon are equivalent when they are similar in body size [14]. Predation and redd superimposition are also thought to be involved in the impact of rainbow trout on masu salmon [13,33].…”

Section: Discussionmentioning

confidence: 99%

“…It was first introduced into Hokkaido in 1920, and has successfully established populations in many river systems where native salmonid species occur, such as the masu salmon O. masou and the white-spotted charr [12]. Some experimental studies have suggested that the rainbow trout does not thoroughly dominate the native species, especially the masu salmon, by interspecific interference competition (direct aggression; [13,14]). Moreover, the rainbow trout prefers a deeper range in the water column than the masu salmon does in these streams, suggesting that the rainbow trout naturally occupies a different habitat niche from that of the masu salmon [15].…”

Section: Introductionmentioning

confidence: 99%

Habitat niche separation of the nonnative rainbow trout and native masu salmon in the Atsuta River, Hokkaido, Japan

2010

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The mechanisms by which nonnative species establish populations can be classified into two broad categories: they usurp the niches of native species through interspecific competition, or they avoid this intense interspecific competition by making use of minimal niche overlap with the native species. In this study, we considered how a nonnative salmonid species, the rainbow trout Oncorhynchus mykiss, established a population in the presence of the native salmonid species, the masu salmon O. masou, in Hokkaido, Japan. Circumstantial field evidence shows that the masu salmon exceeds the rainbow trout in abundance and suggests that these species use different types of cover habitat (rainbow trout abundance increases with increasing abundance of large woody debris aggregates, whereas masu salmon abundance increases with increasing abundance of undercut banks). These results imply that the rainbow trout established a population due to minimal niche overlap with the masu salmon, and not by competitive exclusion of the native species.

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Comparison of competitive ability between native and introduced salmonids: evidence from pairwise contests

Cited by 55 publications

References 26 publications

Invading rainbow trout usurp a terrestrial prey subsidy from native charr and reduce their growth and abundance

Invading rainbow trout usurp a terrestrial prey subsidy from native charr and reduce their growth and abundance

Differences in longitudinal distribution patterns along a Honshu stream of brown trout Salmo trutta, white-spotted charr Salvelinus leucomaenis and masu salmon Oncorhynchus masou

Habitat niche separation of the nonnative rainbow trout and native masu salmon in the Atsuta River, Hokkaido, Japan

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