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Characterizing the trophic niches of stocked and resident cyprinid fishes: consistency in partitioning over time, space and body sizes

View Article: PubMed Central - PubMed

ABSTRACT

Hatchery‐reared fish are commonly stocked into freshwaters to enhance recreational angling. As these fishes are often of high trophic position and attain relatively large sizes, they potentially interact with functionally similar resident fishes and modify food‐web structure. Hatchery‐reared barbel Barbus barbus are frequently stocked to enhance riverine cyprinid fish communities in Europe; these fish can survive for over 20 years and exceed 8 kg. Here, their trophic consequences for resident fish communities were tested using cohabitation studies, mainly involving chub Squalius cephalus, a similarly large‐bodied, omnivorous and long‐lived species. These studies were completed over three spatial scales: pond mesocosms, two streams and three lowland rivers, and used stable isotope analysis. Experiments in mesocosms over 100 days revealed rapid formation of dietary specializations and discrete trophic niches in juvenile B. barbus and S. cephalus. This niche partitioning between the species was also apparent in the streams over 2 years. In the lowland rivers, where fish were mature individuals within established populations, this pattern was also generally apparent in fishes of much larger body sizes. Thus, the stocking of these hatchery‐reared fish only incurred minor consequences for the trophic ecology of resident fish, with strong patterns of trophic niche partitioning and diet specialization. Application of these results to decision‐making frameworks should enable managers to make objective decisions on whether cyprinid fish should be stocked into lowland rivers according to ecological risk.

No MeSH data available.


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Stable isotope bi‐plots for the Site 1 (Top) and 2 (Middle) on the Great Ouse, and the River Avon (Bottom), where (○) Barbus barbus individuals, (Δ) Squalius cephalus individuals and (+) Leuciscus leuciscus individuals with mean (± SE) values of putative food sources: macro‐invertebrates (●) and signal crayfish (■). Solid lines enclose the standard ellipse areas for each species, where black: B. barbus, dark grey: S. cephalus, light grey: L. leuciscus. Note the different scales on the axes.
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ece32272-fig-0006: Stable isotope bi‐plots for the Site 1 (Top) and 2 (Middle) on the Great Ouse, and the River Avon (Bottom), where (○) Barbus barbus individuals, (Δ) Squalius cephalus individuals and (+) Leuciscus leuciscus individuals with mean (± SE) values of putative food sources: macro‐invertebrates (●) and signal crayfish (■). Solid lines enclose the standard ellipse areas for each species, where black: B. barbus, dark grey: S. cephalus, light grey: L. leuciscus. Note the different scales on the axes.

Mentions: The fish sampled across the three rivers tended to be the largest used in the study, with some B. barbus present in samples >600 mm (Table 4). In the River Lea, two size classes of B. barbus and S. cephalus were present and so were analyzed and tested separately. As with the second pond mesocosm experiment and the side channels, the extent of the trophic overlap of B. barbus with other cyprinid species was minimal (Table 4; Figs. 5, 6). This was the case for both size classes of fish in the River Lea, although there was some shift in this pattern between the size classes (Fig. 5). In the fish of lengths 186–237, the B. barbus stable isotopes were nitrogen enriched by approximately 3‰ compared to S. cephalus, but had similar values of δ13C (Table 4; Fig. 5). By contrast, for the fish of above 400 mm, the B. barbus has enriched δ13C and δ15N compared to S. cephalus (Table 4; Fig. 5).


Characterizing the trophic niches of stocked and resident cyprinid fishes: consistency in partitioning over time, space and body sizes
Stable isotope bi‐plots for the Site 1 (Top) and 2 (Middle) on the Great Ouse, and the River Avon (Bottom), where (○) Barbus barbus individuals, (Δ) Squalius cephalus individuals and (+) Leuciscus leuciscus individuals with mean (± SE) values of putative food sources: macro‐invertebrates (●) and signal crayfish (■). Solid lines enclose the standard ellipse areas for each species, where black: B. barbus, dark grey: S. cephalus, light grey: L. leuciscus. Note the different scales on the axes.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4979730&req=5

ece32272-fig-0006: Stable isotope bi‐plots for the Site 1 (Top) and 2 (Middle) on the Great Ouse, and the River Avon (Bottom), where (○) Barbus barbus individuals, (Δ) Squalius cephalus individuals and (+) Leuciscus leuciscus individuals with mean (± SE) values of putative food sources: macro‐invertebrates (●) and signal crayfish (■). Solid lines enclose the standard ellipse areas for each species, where black: B. barbus, dark grey: S. cephalus, light grey: L. leuciscus. Note the different scales on the axes.
Mentions: The fish sampled across the three rivers tended to be the largest used in the study, with some B. barbus present in samples >600 mm (Table 4). In the River Lea, two size classes of B. barbus and S. cephalus were present and so were analyzed and tested separately. As with the second pond mesocosm experiment and the side channels, the extent of the trophic overlap of B. barbus with other cyprinid species was minimal (Table 4; Figs. 5, 6). This was the case for both size classes of fish in the River Lea, although there was some shift in this pattern between the size classes (Fig. 5). In the fish of lengths 186–237, the B. barbus stable isotopes were nitrogen enriched by approximately 3‰ compared to S. cephalus, but had similar values of δ13C (Table 4; Fig. 5). By contrast, for the fish of above 400 mm, the B. barbus has enriched δ13C and δ15N compared to S. cephalus (Table 4; Fig. 5).

View Article: PubMed Central - PubMed

ABSTRACT

Hatchery‐reared fish are commonly stocked into freshwaters to enhance recreational angling. As these fishes are often of high trophic position and attain relatively large sizes, they potentially interact with functionally similar resident fishes and modify food‐web structure. Hatchery‐reared barbel Barbus barbus are frequently stocked to enhance riverine cyprinid fish communities in Europe; these fish can survive for over 20 years and exceed 8 kg. Here, their trophic consequences for resident fish communities were tested using cohabitation studies, mainly involving chub Squalius cephalus, a similarly large‐bodied, omnivorous and long‐lived species. These studies were completed over three spatial scales: pond mesocosms, two streams and three lowland rivers, and used stable isotope analysis. Experiments in mesocosms over 100 days revealed rapid formation of dietary specializations and discrete trophic niches in juvenile B. barbus and S. cephalus. This niche partitioning between the species was also apparent in the streams over 2 years. In the lowland rivers, where fish were mature individuals within established populations, this pattern was also generally apparent in fishes of much larger body sizes. Thus, the stocking of these hatchery‐reared fish only incurred minor consequences for the trophic ecology of resident fish, with strong patterns of trophic niche partitioning and diet specialization. Application of these results to decision‐making frameworks should enable managers to make objective decisions on whether cyprinid fish should be stocked into lowland rivers according to ecological risk.

No MeSH data available.


Related in: MedlinePlus