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.

Benthic Invertebrate Fauna and Feeding Relationships of Brown Trout, Salmo trutta Linnaeus, and River Blackfish, Gadopsis marmoratus Richardson, in the Aberfeldy River, Victoria

1978 ◽  
Vol 29 (6) ◽  
pp. 725 ◽  
Author(s):  
PD Jackson
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Rank Correlation ◽  
Correlation Coefficients ◽  
Benthic Invertebrate ◽  
Invertebrate Fauna ◽  
Kendall Rank Correlation ◽  
Brown Trout Salmo Trutta

The benthic invertebrate fauna and the stomachs of brown trout and river blackfish in a section of the Aberfeldy River, Victoria, were sampled regularly from October 1971 to November 1972. The ranges of food organisms utilized by the two species were very similar as were the proportions of the different food categories. Kendall rank correlation coefficients indicated that the diets of the two fishes were similar on all but the July sampling date. Due to apparent differences in habitat prefer- ences this similarity in diets may be regarded as giving rise to indirect competition.

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.

scholarly journals A comparison of trends in population size and life history features of Atlantic salmon (Salmo salar) and anadromous and non-anadromous Brown trout (Salmo trutta) in a single catchment over 116 years

Hydrobiologia ◽  
2021 ◽  
Author(s):  
Colin E. Adams ◽  
Hannele M. Honkanen ◽  
Ellen Bryson ◽  
Isabel E. Moore ◽  
Malcolm MacCormick ◽  
...  
Keyword(s):  
Time Series ◽  
Atlantic Salmon ◽  
Brown Trout ◽  
Salmo Trutta ◽  
Relative Proportion ◽  
Population Trends ◽  
Sea Trout ◽  
Salmon Population ◽  
Brown Trout Salmo Trutta ◽  
Long Time

AbstractWe use a long time series of catch abundance from a recreational fishery over 116 years to look for population trends in Atlantic salmon, and anadromous (sea trout) and non-anadromous (brown) trout for a single catchment, Loch Lomond, west central Scotland. Year strongly predicted variation in catches but catch effort did not meaningfully increase explained variation. Salmon showed periods of increasing and decreasing trends, for sea trout and brown trout there was an overall declining trend. Since 1952, Lomond salmon population trends differed from both wider Scotland and southern Europe, indicating that the Lomond population is partially buffered from drivers of change in salmon populations more widely. In contrast Lomond sea trout showed a similar declining trend to that of populations from the wider west of Scotland over this period. The Lomond populations showed some evidence of shorter-term cycling patterns; the drivers for which are unknown. Body size in salmon and sea trout declined but increased in brown trout; salmon returned to freshwater later, and the relative proportion of all caught trout that were anadromous increased across the time series. This study shows a long and protracted period of fundamental change to populations of these two species over 116 years.

scholarly journals Regional analysis of multivariate compound coastal flooding potential around Europe and environs: sensitivity analysis and spatial patterns

2021 ◽  
Vol 21 (7) ◽  
pp. 2021-2040
Author(s):  
Paula Camus ◽  
Ivan D. Haigh ◽  
Ahmed A. Nasr ◽  
Thomas Wahl ◽  
Stephen E. Darby ◽  
...  
Keyword(s):  
Time Window ◽  
North Atlantic Ocean ◽  
Regional Analysis ◽  
Rank Correlation ◽  
Correlation Coefficients ◽  
Northern Coast ◽  
The North ◽  
Run Off ◽  
Kendall Rank Correlation ◽  
Driver Assessment

Abstract. In coastal regions, floods can arise through a combination of multiple drivers, including direct surface run-off, river discharge, storm surge, and waves. In this study, we analyse compound flood potential in Europe and environs caused by these four main flooding sources using state-of-the-art databases with coherent forcing (i.e. ERA5). First, we analyse the sensitivity of the compound flooding potential to several factors: (1) sampling method, (2) time window to select the concurrent event of the conditioned driver, (3) dependence metrics, and (4) wave-driven sea level definition. We observe higher correlation coefficients using annual maxima than peaks over threshold. Regarding the other factors, our results show similar spatial distributions of the compound flooding potential. Second, the dependence between the pairs of drivers using the Kendall rank correlation coefficient and the joint occurrence are synthesized for coherent patterns of compound flooding potential using a clustering technique. This quantitative multi-driver assessment not only distinguishes where overall compound flooding potential is the highest, but also discriminates which driver combinations are more likely to contribute to compound flooding. We identify that hotspots of compound flooding potential are located along the southern coast of the North Atlantic Ocean and the northern coast of the Mediterranean Sea.

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 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.

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