Role of visual barriers on mitigation of interspecific interference competition between native and non-native salmonid species

2009 ◽  
Vol 87 (9) ◽  
pp. 781-786 ◽  
Author(s):  
Koh Hasegawa ◽  
Koji Maekawa
Keyword(s):  
Interspecific Competition ◽  
Relative Intensity ◽  
Native Species ◽  
Salmo Trutta ◽  
Woody Debris ◽  
Interference Competition ◽  
Potential Method ◽  
Salvelinus Leucomaenis ◽  
Brown Trout Salmo Trutta ◽  
Native Salmonids

Interspecific competition is a mechanism by which native salmonids can be replaced by non-native species. According to the two-species Lotka–Volterra competition model, replacement of the native species would occur when the non-native species has a competitive advantage over the native species and interspecific competition is more intense than competition within each of the two species. However, field observations have implied that visual barriers such as woody debris may slow down the replacement by mitigating interspecific competition. Using an experimental stream with white-spotted charr ( Salvelinus leucomaenis (Pallas, 1814)) as the native species and brown trout ( Salmo trutta L., 1758) as the non-native species, this study examined aggressive actions within and between species to assess the relative intensities of interspecific and intraspecific competitons within native species and the effect of visual barriers for reducing the relative intensity. In a sympatric and no-barrier treatment where trout was the dominant species, interspecific competition occurred more intensely than intraspecific competition among native charr. However, the relative intensity of interspecific competition decreased in a sympatric and with-barrier treatment. Our results suggest that interspecific competition may contribute to the replacement of native species by more competitive, non-native species. However, restoring visual barriers is a potential method to mitigate interference interactions and may deter the replacement.

Potential of habitat complexity for mitigating interference competition between native and non-native salmonid species

2008 ◽  
Vol 86 (5) ◽  
pp. 386-393 ◽  
Author(s):  
Koh Hasegawa ◽  
Koji Maekawa
Keyword(s):  
Brown Trout ◽  
Habitat Complexity ◽  
Salmo Trutta ◽  
Woody Debris ◽  
Interference Competition ◽  
Salvelinus Leucomaenis ◽  
Salmonid Species ◽  
Local Abundance ◽  
Native White ◽  
White Spotted Char

This study aimed to confirm the mitigation effect of structurally complex habitat on interspecific interference competition between native and non-native salmonid species. We evaluated the effects of habitat complexity (number and size of aggregates of large woody debris and length of undercut banks) and other habitat components that were related to the local abundance of salmonids (dimension and mean depth of pool, mean particle size, and mean current velocity) on the local abundance of native white-spotted char ( Salvelinus leucomaenis (Pallas, 1814)) in allopatry and sympatry with non-native brown trout ( Salmo trutta L., 1758). The field survey was conducted in a Japanese montane stream. The number of char in pool habitats in the allopatric area correlated positively with habitat size, i.e., pool dimension. The number of char in the sympatric area with trout was positively correlated with habitat complexity, while it was negatively correlated with number of trout. In this study, we found that structurally complex habitats might be effective in mitigating interspecific competition between native white-spotted char and non-native brown trout in a montane stream.

Stable isotope niche convergence in coexisting native and non-native salmonids across age classes

2020 ◽  
Vol 77 (8) ◽  
pp. 1359-1365 ◽  
Author(s):  
Julien Cucherousset ◽  
Libor Závorka ◽  
Sergine Ponsard ◽  
Régis Céréghino ◽  
Frédéric Santoul
Keyword(s):  
Stable Isotope ◽  
Brown Trout ◽  
Brook Trout ◽  
Native Species ◽  
Salmo Trutta ◽  
Niche Overlap ◽  
Age Classes ◽  
Terrestrial Invertebrates ◽  
Brown Trout Salmo Trutta ◽  
Native Salmonids

Niche divergence resulting from coevolution is commonly believed to favour coexistence among competing species; however, recent investigations have demonstrated that an unexpected niche convergence can occur when native and non-native species coexist. Yet, our understanding of the ontogenetic characteristics of this niche convergence remains limited. In the present study, we quantified the stable isotope niche of native brown trout (Salmo trutta) in allopatry and sympatry with non-native brook trout (Salvelinus fontinalis) across four age classes. Our results demonstrated that brown trout displayed a stable isotope niche closer to brook trout in sympatry than in allopatry, which was likely driven by an increased consumption of terrestrial invertebrates by sympatric brown trout. Stable isotope niche overlap was the strongest for young-of-the-year individuals and the intensity of overlap between sympatric native brown trout and non-native brook trout decreased during ontogeny. These findings indicate that niche convergence between the species occur at the earliest age class of the native species and are maintained across ontogeny.

scholarly journals Conservation of endangered galaxiid fishes in the Falkland Islands requires urgent action on invasive brown trout

2021 ◽  
Author(s):  
Jessica F. Minett ◽  
Daniel M. Fowler ◽  
Josh Jones ◽  
Paul Brickle ◽  
Glen T. Crossin ◽  
...  
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Legal Protection ◽  
Falkland Islands ◽  
Historical Records ◽  
Establishment Success ◽  
Freshwater Habitats ◽  
Brown Trout Salmo Trutta ◽  
Native Salmonids ◽  
Urgent Action

Non-native salmonids are protected in the Southern hemisphere where they sustain aquaculture and valuable sport fisheries, but also impact on native galaxiid fishes, which poses a conservation conundrum. Legal protection and human-assisted secondary releases may have helped salmonids to spread, but this has seldom been tested. We reconstructed the introduction of brown trout (Salmo trutta) to the Falkland Islands using historical records and modelled its dispersal. Our results indicate that establishment success was ~88%, and that dispersal was facilitated by proximity to introduction sites and density of stream-road crossings, suggesting it was human assisted. Brown trout has already invaded 54% of Falkland rivers, which are 2.9-4.5 times less likely to contain native galaxiids than uninvaded streams. Without strong containment we predict brown trout will invade nearly all suitable freshwater habitats in the Falklands within the next ~70 years, which might put native freshwater fishes at a high risk of extinction

Effects of woody debris on the growth and behaviour of brown trout in experimental stream channels

1998 ◽  
Vol 76 (1) ◽  
pp. 56-61 ◽  
Author(s):  
Karl Sundbaum ◽  
Ingemar Näslund
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Woody Debris ◽  
Feeding Activity ◽  
Control Channel ◽  
Invertebrate Drift ◽  
Stream Channels ◽  
Gravel Bed ◽  
Brown Trout Salmo Trutta ◽  
Experimental Stream

We examined the effects of woody debris on the growth and behaviour of brown trout (Salmo trutta) in experimental stream channels. Two types of habitat were used in the study: a complex habitat created by placing woody debris on a gravel bed and a uniform habitat consisting of a gravel bed only. The experiment was run both outdoors with wild fish that fed on natural invertebrate drift and indoors with hatchery fish that were fed artificial food. In both treatments most of the fish lost mass. In all trials, however, the fish in the woody debris channel lost less mass than the fish in the control channel. Study of the fishes' behaviour revealed less swimming activity, less aggression, and less feeding activity in the woody debris channel than in the control channel. The results of this study indicate that the presence of woody debris decreases intraspecific competition through visual isolation, allowing fish to reduce aggressive interactions and energy expenditure.

scholarly journals Long-term monitoring reveals the success of salmonid habitat restoration

2016 ◽  
Vol 73 (12) ◽  
pp. 1733-1741 ◽  
Author(s):  
Pauliina Louhi ◽  
Teppo Vehanen ◽  
Ari Huusko ◽  
Aki Mäki-Petäys ◽  
Timo Muotka
Keyword(s):  
Salmo Trutta ◽  
Habitat Restoration ◽  
Woody Debris ◽  
Stream Habitat ◽  
Age Classes ◽  
Brown Trout Salmo Trutta ◽  
Extreme Hydrological Events ◽  
Juvenile Brown Trout ◽  
Forest Streams

The growing concern on declining salmonid populations has resulted in numerous restoration projects with variable responses worldwide. In this spatially replicated multiyear study, we assessed the long-term (12 years postrestoration) effects of in-stream habitat restoration (i.e., addition of boulders or large woody debris (LWD) together with boulders) on densities of three age-classes of juvenile brown trout (Salmo trutta) in six forest streams in northern Finland. LWD combined with boulders was more beneficial, particularly for the larger trout (age-2 and older), than were boulder structures alone, indicating that the more diverse habitat created by LWD may have provided a safeguard against drought for the larger fish. Density of age-0+ trout showed a significant long-term increase in boulder-restored sections, providing evidence that log structures may need to be complemented by stony enhancement structures to guarantee the availability of suitable stream habitat for all trout age-classes. As trout densities are known to exhibit inherently wide interannual variability that tracks climatically induced hydrological variation, long-term postrestoration monitoring that encompasses extreme hydrological events is critical for evaluating the success of restoration projects.

Feeding relationships of galaxiids, bullies, eels and trout in a New Zealand river

1975 ◽  
Vol 26 (3) ◽  
pp. 299 ◽  
Author(s):  
PL Cadwallader
Keyword(s):  
New Zealand ◽  
Native Species ◽  
Salmo Trutta ◽  
Relative Proportion ◽  
Rank Correlation ◽  
Correlation Coefficients ◽  
Food Type ◽  
Kendall Rank Correlation ◽  
Direct Competition ◽  
Brown Trout Salmo Trutta

The feeding relationships of the common river galaxias, Galaxias vulgaris Stokell, upland bully, Gobiomorphus breviceps (Stokell), long-finned eel, Anguilla diefenbachii Gray, short-finned eel, A. australis schmidtii Phillipps, and brown trout, Salmo trutta L., were examined in the Glentui River, Canterbury, New Zealand, in February, May and November 1971. With few exceptions, the same food organisms were utilized by all species, but the relative proportion of each food type in the diet varied between species. Kendall rank correlation coefficients indicated that the diets of native fish were dissimilar, with the exception of galaxiids and bullies in May, but in six out of nine comparisons involving the introduced trout, the coefficients indicated varying degrees of similarity with the diets of the native species. Since their feeding mechanisms and feeding localities are different, similarities in the diets of eels and trout, trout and bullies, and bullies and galaxiids can be regarded as giving rise to indirect competition. However, since trout (C 200 mm long) and galaxiids occupy the same microhabitat and feed in the same manner, similarity in their diets can be regarded as giving rise to direct competition. Such direct competition for food, combined with interspecific aggression and similar microhabitat requirements, may help to explain the reduction in abundance of other galaxiids in areas in which trout have been introduced.

scholarly journals Within-stream phenotypic divergence in head shape of brown trout associated with invasive brook trout

2019 ◽  
Vol 129 (2) ◽  
pp. 347-355 ◽  
Author(s):  
Libor Závorka ◽  
Nicolas Larranaga ◽  
Magnus Lovén Wallerius ◽  
Joacim Näslund ◽  
Barbara Koeck ◽  
...  
Keyword(s):  
Brown Trout ◽  
Brook Trout ◽  
Native Species ◽  
Salmo Trutta ◽  
Morphological Changes ◽  
Foraging Strategies ◽  
The Novel ◽  
Head Shape ◽  
Apparent Survival ◽  
Brown Trout Salmo Trutta

Abstract Competition with a non-native species can lead to morphological changes in native organisms induced by phenotypic plasticity, and by selection against individuals that do not adjust their morphology to the novel selection pressure. The morphological changes in native organisms are often associated with rapid behavioural responses to competition with the invader. However, knowledge of the interaction between the behaviour and morphology of native organisms competing with a non-native species remains scarce. Here, we investigated the effect of competition with non-native brook trout Salvelinus fontinalis on head shape of native brown trout Salmo trutta in a stream system where changes in diet and territorial behaviour of sympatric brown trout have previously been demonstrated. We found that sympatric brown trout had smaller eyes, shorter lower jaws and more terminal mouth than allopatric conspecifics. These differences in head shape were highly repeatable over a period of 12 months. Apparent survival indicated that the selection on head shape of brown trout was weaker in the sympatric than in the allopatric stretch of the stream. The results suggest that these changes reinforce divergences of foraging strategies between the allopatric and sympatric brown trout, which can negatively affect their population dynamics and trophic function in the food-web.

Ecological and Genetic Effects of Salmonid Introductions in North America

1991 ◽  
Vol 48 (S1) ◽  
pp. 66-77 ◽  
Author(s):  
C. C. Krueger ◽  
B. May
Keyword(s):  
North America ◽  
North American ◽  
Native Species ◽  
Salmo Trutta ◽  
Management Practice ◽  
Transgenic Fish ◽  
Genetic Effects ◽  
Effective Population ◽  
Management Actions ◽  
Native Salmonids

Stocking of non-native Salmoninae into North American waters began around 1870. Brown trout (Salmo trutta) from Europe established populations across North America and is the only successful inter-continental introduction. Introductions of native salmonids within North America but outside their native ranges have been common. Ecological effects of salmonid introductions. include competition, predation on native salmonids and other fishes, environmental modification through digging of redds in stream bottom substrates during spawning, and introduction of parasites and disease to native fish. Direct genetic effects from stocked salmonids are caused by interbreeding with native species. Indirect genetic effects may result through selective forces and/or a reduction of effective population size, genetic drift, and inbreeding. Management actions used to remove non-native salmonid populations include chemical reclamation and construction of barriers to movement. Salmonid stocking as a management practice is appropriate for species or population rehabilitation. Continued stocking of non-native salmonids should cease where viable native salmonid populations exist. New introductions of Eurasian species should not be made because effects are unpredictable. Aquaculture and the creation of transgenic fish pose special threats to North American salmonids. The era of widespread, intentional introductions of salmonids by man justifiably is drawing to a close.

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