Influences of angler subsidies on the trophic ecology of European barbel Barbus barbus

Santis, Vanessa De; Roberts, Catherine Gutmann; Britton, J. Robert

doi:10.1016/j.fishres.2019.01.028

Cited by 9 publications

(16 citation statements)

References 47 publications

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“…For example, Mehner et al (2019) revealed that after a 3-month exposure period to these baits in a German lake, some omnivorous cyprinid species had diets comprising substantial amounts of these baits. Adult European barbel in 11 English rivers all showed patterns of strong δ 13 C enrichment away from macroinvertebrate putative prey resources, with this enrichment associated with the high consumption of marine fishmeal baits (De Santis et al, 2019), with this also apparent in adult chub Squalius cephalus (Gutmann Roberts & Britton, 2018).…”

Section: Discussionmentioning

confidence: 99%

“…Corn and boilie baits are also strongly δ 13 C enriched versus natural prey resources, with these differences enabling their diet contributions to be quantified after a 3‐month exposure period in the cyprinid fishes (high contribution in some species) and macroinvertebrates (low contribution) of a German lake (Mehner et al, 2019). This isotopic differentiation between natural prey and angler baits means that when fish feed on these baits, it would be expected that their isotopic niche (analogous to the trophic niche; Jackson et al, 2012) would shift to enriched δ 13 C (Bašić et al, 2015; De Santis et al, 2019). The extent of this δ 13 C enrichment would be dependent upon the proportion of angling baits in their diet, with higher proportions resulting in greater shifts (Gutmann Roberts et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Novel trophic subsidies from recreational angling transform the trophic ecology of freshwater fishes

Britton

Almela

2022

Journal of Applied Ecology

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1. Angling is a globally popular leisure activity. There are over 31 million anglers in Europe, many of which target species of the Cyprinidae family in lowland freshwater ecosystems using methods generally involving bait (e.g. groundbaits, seeds and pellets), with large bait inputs possible in periods of high angling activity. While these bait inputs act as novel trophic subsidies ('angling subsidy'), substantial knowledge gaps remain on their influence on freshwater food webs, including on fish trophic niche size and position.2. The effects of angling subsidies on the trophic ecology of cyprinid fish populations and their macroinvertebrate prey resources were investigated in field studies comparing waters of high angling activity ('subsidised fisheries') versus low angling activity ('non-subsidised fisheries'), and complemented by a pond experiment using two cyprinid species in subsidy absence/presence. Methods were based on stable isotope analysis, with angling subsidies being δ 13 C enriched and, generally, δ 15 N depleted compared to macroinvertebrate prey resources.3. In the subsidised fisheries, while there were minimal influences of the baits on macroinvertebrate stable isotope values, the effects of the subsidies on all fish species were to substantially δ 13 C enrich and δ 15 N deplete their isotopic niches.However, patterns of interspecific niche divergence remained similar between the species in subsidy presence.4. In the pond experiment, there was strong isotopic association between the two fish species and macroinvertebrate putative prey in subsidy absence. In treatments that then exposed both species to angling subsidies, their stable isotope values shifted to enriched δ 13 C. Synthesis and application.Where angling activity is high, angling baits can provide strong trophic subsidies to freshwater fish, but with minimal effects on other trophic levels. Their regular input into freshwaters can provide some substantial benefits for fish (e.g. increased growth rates) and fisheries (e.g. elevated carrying capacity, higher catch rates), but can also increase nutrient enrichment and potentially raise concerns on angling ethics. Thus, in allowing the use of

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Novel trophic subsidies from recreational angling transform the trophic ecology of freshwater fishes

Britton

Almela

2022

Journal of Applied Ecology

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“…The relatively high proportion of prey fishes in the diet of the introgressed barbel of TL i aligns to some B. barbus populations having diets in which prey fishes are present, albeit usually in low frequencies (Piria et al 2005 ; Gutmann Roberts et al 2017 ). Recreational anglers also frequently capture larger individuals on baits comprising of high proportions of marine fishmeal, suggesting that fish prey are attractive to adult B. barbus (De Santis et al 2019 ). The barbel of TL i were the only population here where small benthic fishes were detected at relatively high frequency in diet by GCA, despite considerable overlap in the body sizes present, and the presence of small benthic fishes in all sites.…”

Section: Discussionmentioning

confidence: 99%

Biological and trophic consequences of genetic introgression between endemic and invasive Barbus fishes

et al. 2021

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Genetic introgression with native species is recognized as a detrimental impact resulting from biological invasions involving taxonomically similar invaders. Whilst the underlying genetic mechanisms are increasingly understood, the ecological consequences of introgression are relatively less studied, despite their utility for increasing knowledge on how invasion impacts can manifest. Here, the ecological consequences of genetic introgression from an invasive congener were tested using the endemic barbel populations of central Italy, where the invader was the European barbel Barbus barbus. Four populations of native Barbus species (B. plebejus and B. tyberinus) were studied: two purebred and two completely introgressed with alien B. barbus. Across the four populations, differences in their biological traits (growth, body condition and population demographic structure) and trophic ecology (gut content analysis and stable isotope analysis) were tested. While all populations had similar body condition and were dominated by fish up to 2 years of age, the introgressed fish had substantially greater lengths at the same age, with maximum lengths 410–460 mm in hybrids versus 340–360 mm in native purebred barbel. The population characterized by the highest number of introgressed B. barbus alleles (81 %) had the largest trophic niche and a substantially lower trophic position than the other populations through its exploitation of a wider range of resources (e.g. small fishes and plants). These results attest that the genetic introgression of an invasive congener with native species can result in substantial ecological consequences, including the potential for cascading effects.

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“…In rivers in eastern England, they coexist as native species, as barbel is considered indigenous in these areas due to its post‐Pleistocene colonisation of eastern flowing rivers that had connection with the Rhine and Danube (Antognazza et al., 2016; Wheeler & Jordan, 1990). The relatively large body sizes and omnivory of both species suggest they will also share similar prey resources, especially in the absence of recreational angling that can otherwise result in some barbel feeding mainly on angler bait (De Santis et al., 2019). Correspondingly, using a pond mesocosm experiment with chub as the model species and barbel as the co‐existing released species, the experiment tested the relative strength of increased inter‐ and intra‐specific competition on chub somatic growth rates, and their trophic and isotopic niche sizes.…”

Section: Introductionmentioning

confidence: 99%

Trophic consequences of competitive interactions in freshwater fish: Density dependent effects and impacts of inter‐specific versus intra‐specific competition

2020

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Determining the comparative impacts of increased intra‐ versus inter‐specific competition is important in freshwater ecosystems for understanding the ecological changes that can result from activities such as fish stocking events (using alien and/or native fish species), as well as from natural processes that elevate population abundances (e.g. increased annual recruitment success). While increased inter‐specific competition can result in slower growth rates and/or reduced population density in the weaker or less abundant competitor, it is important that this is assessed in relation to the impacts of increased intra‐specific competition. We tested how the strength of inter‐specific competition from a co‐existing species varies with abundance, and how this compares with increased intra‐specific competition. Fish were the model taxa, as their growth rates strongly correlate with competitive success. Replicated pond mesocosms (150 days) used chub Squalius cephalus in an allopatric control (n = 5; C5) and allopatric treatment (n = 10; C10), and in sympatric treatments (n = 5) with European barbel Barbus barbus (n = 5 (T1), 10 (T2) and 15 (T3)). Treatment effects were tested on fish‐specific growth rates (SGRs), and the size and position of the trophic and isotopic niche (stomach contents and stable isotope [SI] analyses respectively). Chub SGRs were significantly higher in C5 versus all other treatments, but did not differ among the other allopatric and sympatric treatments. Chub trophic niche sizes in T1 to T3 were significantly smaller than C5, indicating more specialised diets in the presence of barbel. Chub trophic niche size in C10 was, however, larger than C5 and T1, indicating a shift to a more generalised diet as intra‐specific competition increased. As SGRs reduced in treatments, so did the predicted extent of fish SI turnover, with SI data in T1 to T3 not at isotopic equilibrium with their diet in the mesocosms at the experiment's end. Following conversion of fish SI data to represent values at 95% isotopic turnover, chub isotopic niches also revealed shifts to a more general diet as intra‐specific competition increased, but to more specialised diets as inter‐specific competition increased. Increased intra‐ and inter‐specific competition impacts on the trophic and isotopic niches were contrasting; both metrics indicated niche constrictions in sympatry but niche expansions in allopatry. Impacts on fish growth were evident from both. These results emphasise that the trophic consequences of competition in freshwater fish can differ between stocking events involving the release of conspecifics or other species, with this having important considerations for how freshwater fish communities are managed for angling exploitation.

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Influences of angler subsidies on the trophic ecology of European barbel Barbus barbus

Cited by 9 publications

References 47 publications

Novel trophic subsidies from recreational angling transform the trophic ecology of freshwater fishes

Novel trophic subsidies from recreational angling transform the trophic ecology of freshwater fishes

Biological and trophic consequences of genetic introgression between endemic and invasive Barbus fishes

Trophic consequences of competitive interactions in freshwater fish: Density dependent effects and impacts of inter‐specific versus intra‐specific competition

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