Abiotic factors associated with the occurrence of introduced rainbow trout in the Atsuta River

Kumano, Shigeru; Yamamoto, Toshiaki; Nakagawa, Masanori

doi:10.1007/s10228-010-0151-9

Cited by 7 publications

(4 citation statements)

References 18 publications

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“…In one of the studied tributaries, white-spotted charr were the dominant species during the summer, but masu salmon and rainbow trout were the dominant species during the winter. Species composition of stream salmonids often varies along environmental gradients, and there have been extensive studies of species distribution patterns at various scales (e.g., Fausch et al 1994;Rieman et al 2006;Inoue et al 2009;Kitanishi et al 2010). However, most of these studies have focused on summer distributions and summer temperatures (but see Benjamin et al 2007).…”

Section: Discussionmentioning

confidence: 97%

Seasonal changes in stream salmonid population densities in two tributaries of a boreal river in northern Japan

Morita¹,

Morita²,

Nagasawa³

2011

Ichthyol Res

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We examined seasonal changes in population densities of stream salmonids (masu salmon Oncorhynchus masou, white-spotted charr Salvelinus leucomaenis, and rainbow trout O. mykiss) in two tributaries of the Shoro River, eastern Hokkaido, Japan. In one small tributary, water temperature was relatively high during the winter, and populations of salmon and trout increased through immigration at this time of the year, becoming dominant components of the salmonid assemblage; the density of charr in this stream decreased during the winter, but charr was dominant during the summer. In another medium-sized tributary, the water temperature fell to close to 0°C during the winter, and densities of salmon and charr decreased in this season, through emigration; trout were very rare in this stream. Seasonal patterns of stream salmonid densities vary among species and between localities, resulting in seasonal changes in species composition. For a comprehensive understanding of population processes, a whole-river survey across seasons will be necessary.

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Section: Discussionmentioning

confidence: 97%

Seasonal changes in stream salmonid population densities in two tributaries of a boreal river in northern Japan

Morita¹,

Morita²,

Nagasawa³

2011

Ichthyol Res

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“…Initially, native white‐spotted charr were predominant in the upper river reaches, while rainbow trout were predominant in the middle reaches, and brown trout in the lower reaches (Morita et al, 2004). In some locations in Japan non‐native brown and rainbow trouts prevail in the lower reaches, while native species prevail in the upper river reaches (Hasegawa & Maekawa, 2008; Kitanishi et al, 2010; Yamamoto et al, 2010). The habitat of native species is often segregated along longitudinal gradients, suggesting coexistence mechanisms such as condition‐specific competition exist (Fausch et al, 1994; Taniguchi & Nakano, 2000).…”

Section: Non‐native Species Thrive and Native Species Declinementioning

confidence: 99%

Ups and downs of non‐native and native stream‐dwelling salmonids: Lessons from two contrasting rivers

Morita

2022

Ecological Research

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Freshwater rivers and lakes are particularly vulnerable to anthropogenic disturbance because of their proximity to human occupation. Anthropogenic impacts in fresh water include those caused by dams, water pollution, channelization, and invasive species. One common action to conserve freshwater biodiversity involves supplementing or reintroducing extirpated species, though the benefits of these efforts are controversial. Installation of fishways to dams and removal of invasive alien species has also resulted in recovery of native species. Herein results of long‐term monitoring of salmonids in two rivers in Japan are presented. The first case involves a river above a dam where native white‐spotted charr Salvelinus leucomaenis and masu salmon Oncorhynchus masou declined rapidly in number following dam construction, where non‐native rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta increased in number, and where stocking of native masu salmon was unsuccessful. The second case involves a river formerly dominated by non‐native rainbow trout, in which native Dolly Varden charr Salvelinus curilus and masu salmon increased in numbers following removal of non‐native species and fishway installation. Results reveal natural recovery of masu salmon in a river within which they were once completely extirpated, without stocking. Because salmonids are migratory fish and return to natal rivers, when locally extinct, human intervention to stock or reintroduce them has often been deemed necessary. However, restoration of wildlife would not require stocking or reintroduction if factors that impede the self‐recovery capability of species are removed.

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“…The Atsuta River, located in Hokkaido, Japan (Figure 1; 43°23 0 N, 141°25 0 E), encompasses a watershed area of 136.5 km 2 and extends for approximately 34 km, and is composed of two large (5-10 m in width) and many smaller tributaries (1-2 m in width, Table 1; see also Kitanishi, Yamamoto, & Nakagawa, 2010). One tributary, SG, contains a waterfall at the mouth of the tributary (c. 3 m height), although anadromous fish can still move up this tributary except during times of drought.…”

Section: Study Area and Sample Collectionmentioning

confidence: 99%

“…Characteristics of each tributary measured from 1:20,000 scale topographic map. This table was modified fromTable 1inKitanishi et al (2010) …”

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confidence: 99%

Short‐term temporal instability in fine‐scale genetic structure of masu salmon

2017

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Identifying spatial extent and temporal patterns of population genetic structure is important for understanding evolutionary relationships among local populations and for designing conservation programmes. However, little attention has been devoted to understand whether genetic structure is temporally stable or unstable, and how genetic characteristics may change over time. The goal of this study was to assess the temporal stability of the genetic structure of masu salmon (Oncorhynchus masou). To examine the temporal component of genetic variation in genetic structuring within a river system, we used 810 masu salmon collected from eight tributaries of the Atsuta River, Hokkaido, Japan, over three consecutive years (i.e. 2007–09). We assessed the temporal stability of the genetic structure in 15 microsatellite loci by comparing genetic diversity, effective population size and the relationships between genetic and geographical distances among samples collected from different tributaries and over time. Significant genetic differences were observed among most of the temporal samples collected from the same tributary, and analysis of molecular variance indicated that the temporal component explained about 10 times more of the genetic variation (1.98%) than did the spatial component (0.18%). Isolation by distance (IBD) was detected only in 2009. In addition, a significant correlation in population genetic structure was observed between samples collected in 2008 and those in 2009. In 2007, decomposed pairwise regression analysis identified one population as an outlier population and, following exclusion of the outlier sample, IBD was observed in 2007. This population is small and physically isolated by waterfall, in which the effective population size or effective number of breeders would be expected to be small. We found that fine‐scale genetic structure in masu salmon populations was temporally unstable, due perhaps to genetic drift in small isolated populations, temporal changes in environmental conditions (e.g. drought), and a combination of these factors. This study also highlights that the genetic structure among populations could easily be affected by temporal and/or sampling issues. Studies focused on temporal genetic structuring are likely to be important for conservation of species inhabiting unstable or isolated habitats such as freshwater fish.

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Abiotic factors associated with the occurrence of introduced rainbow trout in the Atsuta River

Cited by 7 publications

References 18 publications

Seasonal changes in stream salmonid population densities in two tributaries of a boreal river in northern Japan

Seasonal changes in stream salmonid population densities in two tributaries of a boreal river in northern Japan

Ups and downs of non‐native and native stream‐dwelling salmonids: Lessons from two contrasting rivers

Short‐term temporal instability in fine‐scale genetic structure of masu salmon

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