The Experts below are selected from a list of 9222 Experts worldwide ranked by ideXlab platform
Nicholas Polunin - One of the best experts on this subject based on the ideXlab platform.
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long term changes in the trophic level of the celtic sea fish community and fish market price distribution
Journal of Applied Ecology, 2002Co-Authors: John K. Pinnegar, Carl M Obrien, Nicholas Polunin, Simon JenningsAbstract:Summary 1. The intensive exploitation of fish communities often leads to substantial reductions in the abundance of target species, with ramifications for the structure and stability of the ecosystem as a whole. 2. We explored changes in the mean trophic level of the Celtic Sea (ICES divisions VII f‐j) fish community using commercial landings, survey data and estimates of trophic level derived from the analysis of nitrogen stable isotopes. 3. Our analyses showed that there has been a significant decline in the mean trophic level of survey catches from 1982 to 2000 and a decline in the trophic level of landings from 1946 to 1998. 4. The decline in mean trophic level through time resulted from a reduction in the abundance of large piscivorous fishes and an increase in smaller pelagic species which feed at a lower trophic level. 5. Similar patterns of decline in the trophic level of both catches and landings imply that there have been substantial changes in the underlying structure of the Celtic Sea fish community and not simply a change in fishery preferences. 6. We suggest that the reported changes in trophic structure result from reductions in the spawning stock biomass of traditional target species associated with intensive fishing, together with long-term climate variability. 7. The relative distribution of fish market prices has changed significantly over the past 22 years, with high trophic level species experiencing greater price rises than lower trophic level species. 8. Although decreased abundance of high trophic level species will ultimately have negative economic consequences, the reduction in mean trophic level of the fish community as a whole may allow the system to sustain higher fishery yields. 9. Management objectives in this fishery will depend on the relative values that society attaches to economic profit and protein production.
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Long‐term changes in the trophic level of the Celtic Sea fish community and fish market price distribution
Journal of Applied Ecology, 2002Co-Authors: John K. Pinnegar, Carl M. O'brien, Simon Jennings, Nicholas PoluninAbstract:Summary 1. The intensive exploitation of fish communities often leads to substantial reductions in the abundance of target species, with ramifications for the structure and stability of the ecosystem as a whole. 2. We explored changes in the mean trophic level of the Celtic Sea (ICES divisions VII f‐j) fish community using commercial landings, survey data and estimates of trophic level derived from the analysis of nitrogen stable isotopes. 3. Our analyses showed that there has been a significant decline in the mean trophic level of survey catches from 1982 to 2000 and a decline in the trophic level of landings from 1946 to 1998. 4. The decline in mean trophic level through time resulted from a reduction in the abundance of large piscivorous fishes and an increase in smaller pelagic species which feed at a lower trophic level. 5. Similar patterns of decline in the trophic level of both catches and landings imply that there have been substantial changes in the underlying structure of the Celtic Sea fish community and not simply a change in fishery preferences. 6. We suggest that the reported changes in trophic structure result from reductions in the spawning stock biomass of traditional target species associated with intensive fishing, together with long-term climate variability. 7. The relative distribution of fish market prices has changed significantly over the past 22 years, with high trophic level species experiencing greater price rises than lower trophic level species. 8. Although decreased abundance of high trophic level species will ultimately have negative economic consequences, the reduction in mean trophic level of the fish community as a whole may allow the system to sustain higher fishery yields. 9. Management objectives in this fishery will depend on the relative values that society attaches to economic profit and protein production.
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linking size based and trophic analyses of benthic community structure
Marine Ecology Progress Series, 2002Co-Authors: Simon Jennings, John K. Pinnegar, Nicholas Polunin, Karema J WarrAbstract:Models of biomass size spectra assume that organisms with higher body mass feed at higher trophic levels, but explicit empirical tests of this pattern are rare. We used nitrogen stable isotopes (d15N) as an index of the trophic level in a benthic fish and invertebrate size-spectrum, and demonstrated that body mass was positively and significantly related to trophic level. This pattern was consistent with the expectation that predator-prey relationships led to powerful size-based trophic structuring in marine communities and ecosystems. Further analysis of intra- and interspecific relationships between body mass and trophic level in the community showed that increases in trophic level across the size spectrum were predominantly a consequence of intra-specific increases in trophic level with body mass and not a consequence of larger species (species with greater maximum body mass) feeding at higher trophic levels. We confirmed the absence of strong inter-specific relationships between maximum body mass and trophic level with cross-species and phylogenetic comparative approaches. Size-based models are easier and cheaper to parameterise than most food-web models. Subject to the persistence of relationships between body mass and trophic level in space and time, our results suggest that size spectra could be parameterised with body mass-trophic level relationships and used to describe the trophic structure of some marine communities and ecosystems.
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weak cross species relationships between body size and trophic level belie powerful size based trophic structuring in fish communities
Journal of Animal Ecology, 2001Co-Authors: Simon Jennings, John K. Pinnegar, Nicholas Polunin, Trevor W BoonAbstract:1. Body size determines rates of respiration and production, energy requirements, mortality rates, patterns of predation and vulnerability to mortality. Body size distributions are often used to describe structure and energy flux in communities and ecosystems. 2. If clear relationships can be established between body size and trophic level in fishes, they may provide a basis for integrating community and ecosystem analyses based on size spectra, food webs and life histories. 3. We investigated relationships between the body sizes (weight and length) of northeast Atlantic fishes and their trophic level. The abundance of 15N, as determined by stable isotope analysis, was used as an index of trophic level. 4. Cross-species and comparative analyses demonstrated that body size was unrelated or weakly related to trophic level. Thus allometric relationships between body size and trophic level could not be used to predict the trophic structure of fish communities. 5. The results of the cross-species analyses contrasted with patterns in the size and trophic structure of entire fish communities. When fish communities were divided into size classes, there were strong positive relationships between size class and trophic level. The slope suggested a mean predator: prey body mass ratio of 80:1. 6. Our results suggest that body size does not provide a useful surrogate of trophic level for individual species, but that body size is an excellent predictor of trophic level within the community, providing an empirical basis for integrating community analyses based on models of trophic structure and body size distributions.
John K. Pinnegar - One of the best experts on this subject based on the ideXlab platform.
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long term trends in the trophic structure of the north sea fish community evidence from stable isotope analysis size spectra and community metrics
Marine Biology, 2002Co-Authors: Simon Jennings, John K. Pinnegar, Simon P R Greenstreet, L Hill, G J Piet, Karema J WarrAbstract:Fishing has wide-ranging impacts on marine ecosystems. One of the most pervasive signs of intensive fishing is "fishing down the food web", with landings increasingly dominated by smaller species from lower trophic levels. Decreases in the trophic level of landings are assumed to reflect those in fish communities, because size-selective mortality causes decreases in the relative abundance of larger species and in mean body size within species. However, existing analyses of fishing impacts on the trophic level of fish communities have focused on the role of changes in species composition rather than size composition. This will provide a biased assessment of the magnitude of fishing impacts, because fishes feed at different trophic levels as they grow. Here, we combine body size versus trophic level relationships for North Sea fishes (trophic level assessed using nitrogen stable-isotope analysis) with species–size–abundance data from two time-series of trawl-survey data (whole North Sea 1982–2000, central and northern North Sea 1925–1996) to predict long-term trends in the trophic structure of the North Sea fish community. Analyses of the 1982–2000 time-series showed that there was a slow but progressive decline in the trophic level of the demersal community, while there was no trend in the trophic level of the combined pelagic and demersal community. Analyses of the longer time-series suggested that there was no trend in the trophic level of the demersal community. We related temporal changes in trophic level to temporal changes in the slopes of normalised biomass size-spectra (which theoretically represent the trophic structure of the community), mean log2 body mass and mean log2 maximum body mass. While the size-based metrics of community structure showed long-term trends that were consistent with the effects of increased fishery exploitation, these trends were only correlated with trophic level for the demersal community. Our analysis suggests that the effects of fishing on the trophic structure of fish communities can be much more complex than previously assumed. This is a consequence of sampled communities not reflecting all the pathways of energy transfer in a marine ecosystem and of the absence of historical data on temporal and spatial changes in the trophic level of individuals. For the North Sea fish community, changes in size structure due to the differential effects of fishing on species and populations with different life histories are a stronger and more universal indicator of fishing effects than changes in mean trophic level.
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long term changes in the trophic level of the celtic sea fish community and fish market price distribution
Journal of Applied Ecology, 2002Co-Authors: John K. Pinnegar, Carl M Obrien, Nicholas Polunin, Simon JenningsAbstract:Summary 1. The intensive exploitation of fish communities often leads to substantial reductions in the abundance of target species, with ramifications for the structure and stability of the ecosystem as a whole. 2. We explored changes in the mean trophic level of the Celtic Sea (ICES divisions VII f‐j) fish community using commercial landings, survey data and estimates of trophic level derived from the analysis of nitrogen stable isotopes. 3. Our analyses showed that there has been a significant decline in the mean trophic level of survey catches from 1982 to 2000 and a decline in the trophic level of landings from 1946 to 1998. 4. The decline in mean trophic level through time resulted from a reduction in the abundance of large piscivorous fishes and an increase in smaller pelagic species which feed at a lower trophic level. 5. Similar patterns of decline in the trophic level of both catches and landings imply that there have been substantial changes in the underlying structure of the Celtic Sea fish community and not simply a change in fishery preferences. 6. We suggest that the reported changes in trophic structure result from reductions in the spawning stock biomass of traditional target species associated with intensive fishing, together with long-term climate variability. 7. The relative distribution of fish market prices has changed significantly over the past 22 years, with high trophic level species experiencing greater price rises than lower trophic level species. 8. Although decreased abundance of high trophic level species will ultimately have negative economic consequences, the reduction in mean trophic level of the fish community as a whole may allow the system to sustain higher fishery yields. 9. Management objectives in this fishery will depend on the relative values that society attaches to economic profit and protein production.
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Long‐term changes in the trophic level of the Celtic Sea fish community and fish market price distribution
Journal of Applied Ecology, 2002Co-Authors: John K. Pinnegar, Carl M. O'brien, Simon Jennings, Nicholas PoluninAbstract:Summary 1. The intensive exploitation of fish communities often leads to substantial reductions in the abundance of target species, with ramifications for the structure and stability of the ecosystem as a whole. 2. We explored changes in the mean trophic level of the Celtic Sea (ICES divisions VII f‐j) fish community using commercial landings, survey data and estimates of trophic level derived from the analysis of nitrogen stable isotopes. 3. Our analyses showed that there has been a significant decline in the mean trophic level of survey catches from 1982 to 2000 and a decline in the trophic level of landings from 1946 to 1998. 4. The decline in mean trophic level through time resulted from a reduction in the abundance of large piscivorous fishes and an increase in smaller pelagic species which feed at a lower trophic level. 5. Similar patterns of decline in the trophic level of both catches and landings imply that there have been substantial changes in the underlying structure of the Celtic Sea fish community and not simply a change in fishery preferences. 6. We suggest that the reported changes in trophic structure result from reductions in the spawning stock biomass of traditional target species associated with intensive fishing, together with long-term climate variability. 7. The relative distribution of fish market prices has changed significantly over the past 22 years, with high trophic level species experiencing greater price rises than lower trophic level species. 8. Although decreased abundance of high trophic level species will ultimately have negative economic consequences, the reduction in mean trophic level of the fish community as a whole may allow the system to sustain higher fishery yields. 9. Management objectives in this fishery will depend on the relative values that society attaches to economic profit and protein production.
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linking size based and trophic analyses of benthic community structure
Marine Ecology Progress Series, 2002Co-Authors: Simon Jennings, John K. Pinnegar, Nicholas Polunin, Karema J WarrAbstract:Models of biomass size spectra assume that organisms with higher body mass feed at higher trophic levels, but explicit empirical tests of this pattern are rare. We used nitrogen stable isotopes (d15N) as an index of the trophic level in a benthic fish and invertebrate size-spectrum, and demonstrated that body mass was positively and significantly related to trophic level. This pattern was consistent with the expectation that predator-prey relationships led to powerful size-based trophic structuring in marine communities and ecosystems. Further analysis of intra- and interspecific relationships between body mass and trophic level in the community showed that increases in trophic level across the size spectrum were predominantly a consequence of intra-specific increases in trophic level with body mass and not a consequence of larger species (species with greater maximum body mass) feeding at higher trophic levels. We confirmed the absence of strong inter-specific relationships between maximum body mass and trophic level with cross-species and phylogenetic comparative approaches. Size-based models are easier and cheaper to parameterise than most food-web models. Subject to the persistence of relationships between body mass and trophic level in space and time, our results suggest that size spectra could be parameterised with body mass-trophic level relationships and used to describe the trophic structure of some marine communities and ecosystems.
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weak cross species relationships between body size and trophic level belie powerful size based trophic structuring in fish communities
Journal of Animal Ecology, 2001Co-Authors: Simon Jennings, John K. Pinnegar, Nicholas Polunin, Trevor W BoonAbstract:1. Body size determines rates of respiration and production, energy requirements, mortality rates, patterns of predation and vulnerability to mortality. Body size distributions are often used to describe structure and energy flux in communities and ecosystems. 2. If clear relationships can be established between body size and trophic level in fishes, they may provide a basis for integrating community and ecosystem analyses based on size spectra, food webs and life histories. 3. We investigated relationships between the body sizes (weight and length) of northeast Atlantic fishes and their trophic level. The abundance of 15N, as determined by stable isotope analysis, was used as an index of trophic level. 4. Cross-species and comparative analyses demonstrated that body size was unrelated or weakly related to trophic level. Thus allometric relationships between body size and trophic level could not be used to predict the trophic structure of fish communities. 5. The results of the cross-species analyses contrasted with patterns in the size and trophic structure of entire fish communities. When fish communities were divided into size classes, there were strong positive relationships between size class and trophic level. The slope suggested a mean predator: prey body mass ratio of 80:1. 6. Our results suggest that body size does not provide a useful surrogate of trophic level for individual species, but that body size is an excellent predictor of trophic level within the community, providing an empirical basis for integrating community analyses based on models of trophic structure and body size distributions.
Simon Jennings - One of the best experts on this subject based on the ideXlab platform.
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long term trends in the trophic structure of the north sea fish community evidence from stable isotope analysis size spectra and community metrics
Marine Biology, 2002Co-Authors: Simon Jennings, John K. Pinnegar, Simon P R Greenstreet, L Hill, G J Piet, Karema J WarrAbstract:Fishing has wide-ranging impacts on marine ecosystems. One of the most pervasive signs of intensive fishing is "fishing down the food web", with landings increasingly dominated by smaller species from lower trophic levels. Decreases in the trophic level of landings are assumed to reflect those in fish communities, because size-selective mortality causes decreases in the relative abundance of larger species and in mean body size within species. However, existing analyses of fishing impacts on the trophic level of fish communities have focused on the role of changes in species composition rather than size composition. This will provide a biased assessment of the magnitude of fishing impacts, because fishes feed at different trophic levels as they grow. Here, we combine body size versus trophic level relationships for North Sea fishes (trophic level assessed using nitrogen stable-isotope analysis) with species–size–abundance data from two time-series of trawl-survey data (whole North Sea 1982–2000, central and northern North Sea 1925–1996) to predict long-term trends in the trophic structure of the North Sea fish community. Analyses of the 1982–2000 time-series showed that there was a slow but progressive decline in the trophic level of the demersal community, while there was no trend in the trophic level of the combined pelagic and demersal community. Analyses of the longer time-series suggested that there was no trend in the trophic level of the demersal community. We related temporal changes in trophic level to temporal changes in the slopes of normalised biomass size-spectra (which theoretically represent the trophic structure of the community), mean log2 body mass and mean log2 maximum body mass. While the size-based metrics of community structure showed long-term trends that were consistent with the effects of increased fishery exploitation, these trends were only correlated with trophic level for the demersal community. Our analysis suggests that the effects of fishing on the trophic structure of fish communities can be much more complex than previously assumed. This is a consequence of sampled communities not reflecting all the pathways of energy transfer in a marine ecosystem and of the absence of historical data on temporal and spatial changes in the trophic level of individuals. For the North Sea fish community, changes in size structure due to the differential effects of fishing on species and populations with different life histories are a stronger and more universal indicator of fishing effects than changes in mean trophic level.
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long term changes in the trophic level of the celtic sea fish community and fish market price distribution
Journal of Applied Ecology, 2002Co-Authors: John K. Pinnegar, Carl M Obrien, Nicholas Polunin, Simon JenningsAbstract:Summary 1. The intensive exploitation of fish communities often leads to substantial reductions in the abundance of target species, with ramifications for the structure and stability of the ecosystem as a whole. 2. We explored changes in the mean trophic level of the Celtic Sea (ICES divisions VII f‐j) fish community using commercial landings, survey data and estimates of trophic level derived from the analysis of nitrogen stable isotopes. 3. Our analyses showed that there has been a significant decline in the mean trophic level of survey catches from 1982 to 2000 and a decline in the trophic level of landings from 1946 to 1998. 4. The decline in mean trophic level through time resulted from a reduction in the abundance of large piscivorous fishes and an increase in smaller pelagic species which feed at a lower trophic level. 5. Similar patterns of decline in the trophic level of both catches and landings imply that there have been substantial changes in the underlying structure of the Celtic Sea fish community and not simply a change in fishery preferences. 6. We suggest that the reported changes in trophic structure result from reductions in the spawning stock biomass of traditional target species associated with intensive fishing, together with long-term climate variability. 7. The relative distribution of fish market prices has changed significantly over the past 22 years, with high trophic level species experiencing greater price rises than lower trophic level species. 8. Although decreased abundance of high trophic level species will ultimately have negative economic consequences, the reduction in mean trophic level of the fish community as a whole may allow the system to sustain higher fishery yields. 9. Management objectives in this fishery will depend on the relative values that society attaches to economic profit and protein production.
-
Long‐term changes in the trophic level of the Celtic Sea fish community and fish market price distribution
Journal of Applied Ecology, 2002Co-Authors: John K. Pinnegar, Carl M. O'brien, Simon Jennings, Nicholas PoluninAbstract:Summary 1. The intensive exploitation of fish communities often leads to substantial reductions in the abundance of target species, with ramifications for the structure and stability of the ecosystem as a whole. 2. We explored changes in the mean trophic level of the Celtic Sea (ICES divisions VII f‐j) fish community using commercial landings, survey data and estimates of trophic level derived from the analysis of nitrogen stable isotopes. 3. Our analyses showed that there has been a significant decline in the mean trophic level of survey catches from 1982 to 2000 and a decline in the trophic level of landings from 1946 to 1998. 4. The decline in mean trophic level through time resulted from a reduction in the abundance of large piscivorous fishes and an increase in smaller pelagic species which feed at a lower trophic level. 5. Similar patterns of decline in the trophic level of both catches and landings imply that there have been substantial changes in the underlying structure of the Celtic Sea fish community and not simply a change in fishery preferences. 6. We suggest that the reported changes in trophic structure result from reductions in the spawning stock biomass of traditional target species associated with intensive fishing, together with long-term climate variability. 7. The relative distribution of fish market prices has changed significantly over the past 22 years, with high trophic level species experiencing greater price rises than lower trophic level species. 8. Although decreased abundance of high trophic level species will ultimately have negative economic consequences, the reduction in mean trophic level of the fish community as a whole may allow the system to sustain higher fishery yields. 9. Management objectives in this fishery will depend on the relative values that society attaches to economic profit and protein production.
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linking size based and trophic analyses of benthic community structure
Marine Ecology Progress Series, 2002Co-Authors: Simon Jennings, John K. Pinnegar, Nicholas Polunin, Karema J WarrAbstract:Models of biomass size spectra assume that organisms with higher body mass feed at higher trophic levels, but explicit empirical tests of this pattern are rare. We used nitrogen stable isotopes (d15N) as an index of the trophic level in a benthic fish and invertebrate size-spectrum, and demonstrated that body mass was positively and significantly related to trophic level. This pattern was consistent with the expectation that predator-prey relationships led to powerful size-based trophic structuring in marine communities and ecosystems. Further analysis of intra- and interspecific relationships between body mass and trophic level in the community showed that increases in trophic level across the size spectrum were predominantly a consequence of intra-specific increases in trophic level with body mass and not a consequence of larger species (species with greater maximum body mass) feeding at higher trophic levels. We confirmed the absence of strong inter-specific relationships between maximum body mass and trophic level with cross-species and phylogenetic comparative approaches. Size-based models are easier and cheaper to parameterise than most food-web models. Subject to the persistence of relationships between body mass and trophic level in space and time, our results suggest that size spectra could be parameterised with body mass-trophic level relationships and used to describe the trophic structure of some marine communities and ecosystems.
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weak cross species relationships between body size and trophic level belie powerful size based trophic structuring in fish communities
Journal of Animal Ecology, 2001Co-Authors: Simon Jennings, John K. Pinnegar, Nicholas Polunin, Trevor W BoonAbstract:1. Body size determines rates of respiration and production, energy requirements, mortality rates, patterns of predation and vulnerability to mortality. Body size distributions are often used to describe structure and energy flux in communities and ecosystems. 2. If clear relationships can be established between body size and trophic level in fishes, they may provide a basis for integrating community and ecosystem analyses based on size spectra, food webs and life histories. 3. We investigated relationships between the body sizes (weight and length) of northeast Atlantic fishes and their trophic level. The abundance of 15N, as determined by stable isotope analysis, was used as an index of trophic level. 4. Cross-species and comparative analyses demonstrated that body size was unrelated or weakly related to trophic level. Thus allometric relationships between body size and trophic level could not be used to predict the trophic structure of fish communities. 5. The results of the cross-species analyses contrasted with patterns in the size and trophic structure of entire fish communities. When fish communities were divided into size classes, there were strong positive relationships between size class and trophic level. The slope suggested a mean predator: prey body mass ratio of 80:1. 6. Our results suggest that body size does not provide a useful surrogate of trophic level for individual species, but that body size is an excellent predictor of trophic level within the community, providing an empirical basis for integrating community analyses based on models of trophic structure and body size distributions.
Robert Arlinghaus - One of the best experts on this subject based on the ideXlab platform.
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Size-dependent foraging niches of European Perch Perca fluviatilis (Linnaeus, 1758) and North American Yellow Perch Perca flavescens (Mitchill, 1814)
Environmental Biology of Fishes, 2018Co-Authors: Stefan M. Linzmaier, Laura A. Twardochleb, Julian D. Olden, Thomas Mehner, Robert ArlinghausAbstract:Body size of consumer species is a fundamental trait that influences the trophic ecology of individuals and their contribution to the functioning of freshwater ecosystems. However, the relationship between body size and trophic ecology can be highly variable both within and between closely-related and similarly-sized species. In this study we compared the intra- and interspecific relationship between body size and trophic position for North American Yellow Perch Perca flavescens and European Perch Perca fluviatilis , which share similarities in morphology, life history traits and trophic requirements. We used stable isotope ratios (δ^15N and δ^13C) to characterize differences in size-dependency of trophic position and to trace consumer foraging history of Yellow Perch in lakes in the Northwestern United States and European Perch in lakes in Germany. The trophic position and stable isotope ratios of Yellow Perch and European Perch steadily increased with total body length, but European Perch were consistently feeding at higher trophic positions than Yellow Perch at a given length. European Perch occupied considerably higher trophic positions (mean trophic position = 3.9) than Yellow Perch (mean trophic position = 2.8). Large European Perch were increasingly piscivorous, whereas large Yellow Perch were more opportunistic and omnivorous predators of invertebrate prey. Overall, the trophic position among individual Yellow Perch varied more strongly than in European Perch. We conclude that both species similarly increase in trophic position with size, but the specific size-dependency of both trophic position and resource use varies with taxonomy and local ecological conditions. Thus, body size as a sole measure of trophic position should be considered cautiously when generalizing across populations and species.
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Size-dependent foraging niches of European Perch Perca fluviatilis (Linnaeus, 1758) and North American Yellow Perch Perca flavescens (Mitchill, 1814)
Environmental Biology of Fishes, 2018Co-Authors: Stefan M. Linzmaier, Laura A. Twardochleb, Julian D. Olden, Thomas Mehner, Robert ArlinghausAbstract:Body size of consumer species is a fundamental trait that influences the trophic ecology of individuals and their contribution to the functioning of freshwater ecosystems. However, the relationship between body size and trophic ecology can be highly variable both within and between closely-related and similarly-sized species. In this study we compared the intra- and interspecific relationship between body size and trophic position for North American Yellow Perch Perca flavescens and European Perch Perca fluviatilis , which share similarities in morphology, life history traits and trophic requirements. We used stable isotope ratios (δ^15N and δ^13C) to characterize differences in size-dependency of trophic position and to trace consumer foraging history of Yellow Perch in lakes in the Northwestern United States and European Perch in lakes in Germany. The trophic position and stable isotope ratios of Yellow Perch and European Perch steadily increased with total body length, but European Perch were consistently feeding at higher trophic positions than Yellow Perch at a given length. European Perch occupied considerably higher trophic positions (mean trophic position = 3.9) than Yellow Perch (mean trophic position = 2.8). Large European Perch were increasingly piscivorous, whereas large Yellow Perch were more opportunistic and omnivorous predators of invertebrate prey. Overall, the trophic position among individual Yellow Perch varied more strongly than in European Perch. We conclude that both species similarly increase in trophic position with size, but the specific size-dependency of both trophic position and resource use varies with taxonomy and local ecological conditions. Thus, body size as a sole measure of trophic position should be considered cautiously when generalizing across populations and species.
L. Veselý - One of the best experts on this subject based on the ideXlab platform.
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Temperature and prey density jointly influence trophic and non‐trophic interactions in multiple predator communities
Freshwater Biology, 2019Co-Authors: L. Veselý, D.s. Boukal, M. Buřič, I. Kuklina, B. Yazicioglu, M. Prchal, P. Kozak, A. Kouba, Martin Fořt, Arnaud SentisAbstract:Environmental changes such as global warming can affect ecological communities by altering individual life histories and species interactions. Recent studies focusing on the consequences of environmental change on species interactions highlighted the need for a wider, multi‐species context including both trophic and non‐trophic interactions (e.g. predator interference). However, the effects of biotic and abiotic factors on trophic and non‐trophic interactions remain largely unexplored. To fill this gap, we combined laboratory experiments and functional response modelling to investigate how temperature and prey density influence trophic and non‐trophic interactions in multiple predator communities. The system under study consisted of predatory dragonfly larvae (Aeshna cyanea) and omnivorous marbled crayfish (Procambarus virginalis) preying on common carp fry (Cyprinus carpio). We estimated the functional response of each predator in single‐predator experiments and used this information to disentangle the trophic and non‐trophic interactions and their dependence on environmental conditions in multiple predator trials. We found that consumer identity, prey density, and temperature all affect the magnitude of trophic and non‐trophic interactions. Non‐trophic interactions mostly decreased predator feeding rates, corroborating previous observations that interference prevails in aquatic communities. Moreover, trophic interactions depended primarily on the environmental variables whereas non‐trophic interactions depended mainly on consumer identity. Our results indicate that non‐trophic interactions among true predators and omnivores can be substantial and that biotic and abiotic conditions further modify the magnitude and direction of these interactions, which can affect food web dynamics and stability.
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Temperature and prey density jointly influence trophic and non-trophic interactions in multiple predator communities
Freshwater Biology, 2019Co-Authors: L. Veselý, D.s. Boukal, M. Buřič, I. Kuklina, Myriam Fort, B. Yazicioglu, M. Prchal, P. Kozak, A. Kouba, A. SentisAbstract:Environmental changes such as global warming can affect ecological communities by altering individual life histories and species interactions. Recent studies focusing on the consequences of environmental change on species interactions highlighted the need for a wider, multi-species context including both trophic and non-trophic interactions (e.g. predator interference). However, the effects of biotic and abiotic factors on trophic and non-trophic interactions remain largely unexplored. To fill this gap, we combined laboratory experiments and functional response modelling to investigate how temperature and prey density influence trophic and non-trophic interactions in multiple predator communities. The system under study consisted of predatory dragonfly larvae (Aeshna cyanea) and omnivorous marbled crayfish (Procambarus virginalis) preying on common carp fry (Cyprinus carpio). We estimated the functional response of each predator in single-predator experiments and used this information to disentangle the trophic and non-trophic interactions and their dependence on environmental conditions in multiple predator trials. We found that consumer identity, prey density, and temperature all affect the magnitude of trophic and non-trophic interactions. Non-trophic interactions mostly decreased predator feeding rates, corroborating previous observations that interference prevails in aquatic communities. Moreover, trophic interactions depended primarily on the environmental variables whereas non-trophic interactions depended mainly on consumer identity. Our results indicate that non-trophic interactions among true predators and omnivores can be substantial and that biotic and abiotic conditions further modify the magnitude and direction of these interactions, which can affect food web dynamics and stability.
