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  • Online Resource  (9)
  • Wiley  (9)
  • 2020-2024  (9)
  • 1
    In: Ecology of Freshwater Fish, Wiley, Vol. 33, No. 1 ( 2024-01)
    Abstract: The trophic niche of aquatic generalist predators is influenced by ontogeny, habitat characteristics, availability and type of prey, and competitive interactions. Many interrelated lake characteristics influence the availability of prey and may thereby impact foraging niches and the trajectory of ontogenetic niche shifts. Our work uses Eurasian perch ( Perca fluviatilis ) as a model species to examine the correlation of multiple lake and fish community characteristics with the size‐dependency of perch populations' realised trophic niche. We used carbon and nitrogen stable isotopes to correlate the changes in perch trophic position across a gradient of total lengths in seven gravel pit lakes that differed in lake morphology, habitat heterogeneity, productivity, structural complexity, and fish community composition. Perch populations in lakes with more shallow‐water habitat reached a higher trophic position at smaller sizes than perch in deeper lakes. However, the changes in trophic position with increasing size were less pronounced compared to perch from deeper lakes. Large individuals from the latter perch populations ultimately achieved higher mean trophic positions compared to fish from shallow lakes. Perch in lakes with more shallow‐water habitat may, therefore, achieve lower rates of piscivory because of higher relative availability of macroinvertebrates or greater competition with zooplanktivores. Our results suggest that large, piscivorous perch are more likely to develop in deeper lakes, and that these changes in perch trophic position across ontogeny are more strongly related to the depth of lakes than to the type of structured habitat in the littoral zone.
    Type of Medium: Online Resource
    ISSN: 0906-6691 , 1600-0633
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2024
    detail.hit.zdb_id: 2028166-3
    SSG: 21,3
    SSG: 12
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  • 2
    In: Limnology and Oceanography, Wiley, Vol. 65, No. 4 ( 2020-04), p. 892-902
    Abstract: Fish community feeding and production rates may differ between lakes despite similar fish biomass levels because of differences in size structure and local temperature. Therefore, across‐lake comparisons of the strength and direction of top‐down and bottom‐up fish–phytoplankton relationships should consider these factors. We used the metabolic theory of ecology to calculate size‐ and temperature‐corrected community energy demand (CED om ) and community production (CP) of omnivorous fishes in 227 European lakes from major habitat types (MHTs) of polar freshwaters, temperate floodplain rivers and wetlands, and temperate coastal rivers. We related CED om with total phosphorus (TP)‐corrected chlorophyll a (Chl a ) concentrations to evaluate a potential top‐down directed trophic cascade from fish to phytoplankton. Furthermore, we related Chl a with CP to demonstrate potential bottom‐up effects of phytoplankton on fish. For both analyses, we added the CED of piscivorous fishes (CED pi ) as a predictor to account for potential predation effects on the omnivorous fish community. CED om was weakly positively related with TP‐corrected Chl a , but the strength of the relationship differed between MHTs. In contrast, CP was consistently positively related with Chl a in the entire dataset. CED pi did not contribute to top‐down or bottom‐up relationships. The application of metabolic variables characterizing fish community feeding and production rates makes these results robust because the approach accounted for the usually neglected effects of fish size and temperature in across‐lake comparisons. Our results suggest that bottom‐up effects from phytoplankton on fish secondary production in lakes are substantially stronger than top‐down effects from fish on phytoplankton biomass.
    Type of Medium: Online Resource
    ISSN: 0024-3590 , 1939-5590
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 2033191-5
    detail.hit.zdb_id: 412737-7
    SSG: 12
    SSG: 14
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  • 3
    In: Astronomische Nachrichten, Wiley, Vol. 341, No. 1 ( 2020-01), p. 26-31
    Abstract: We report the serendipitous discovery of a redshift 3.68 quasar while validating the star WD 0308‐565 as a spectrophotometric standard star for the Multi‐Unit Spectroscopic Explorer (MUSE) calibration plan. Based on the MUSE observations, the luminosity of the quasar at 1350A (L1350) is 4.71 × 10 45 erg s −1 . The black hole mass is 2.5 × 10 9   M ʘ , and bolometric luminosity is 1.57 × 10 47 erg s −1 . Present in the field of view of a star in the calibration plan of the instrument makes this a very valuable quasar as it will receive many repeated visits in the coming years making it an ideal candidate for reverberation mapping studies.
    Type of Medium: Online Resource
    ISSN: 0004-6337 , 1521-3994
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2020
    detail.hit.zdb_id: 2025762-4
    detail.hit.zdb_id: 2171222-0
    SSG: 16,12
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  • 4
    In: Diversity and Distributions, Wiley, Vol. 29, No. 8 ( 2023-08), p. 997-1008
    Abstract: The maintenance of broad‐scale connectivity patterns is suggested as a sustainable strategy for biodiversity preservation. However, explicit approaches for quantifying the functional role of different areas in biogeographic connectivity have been elusive. Freshwaters are spatially structured ecosystems critically endangered because of human activities and global change, demanding connectivity‐based approaches for their conservation. Mass effects—the increase in local diversity by immigration—and corridor effects—the connections with distant communities—are basic and relevant mechanisms connecting diversity with landscape configuration. Here, we identified freshwater hotspots areas for mass and corridor effects across Europe. Location Europe. Methods Using satellite images, we quantified the areas of ephemeral, temporal and permanent freshwaters. The landscape structure of the freshwater ecoregions was represented as a directed‐graph, and the link weights were determined by the distance between cells and the water cover. Three centrality metrics were used to rank freshwater areas with respect to their potential role in dispersal‐mediated mechanisms. Out‐degree represents the potential of an area to operate as a diversity source to other regions. In‐degree reflects the importance that incoming dispersal may have in local diversity. Betweenness refers to the importance of local areas for connecting other distant areas. Results We detected great concentrations of source hotspots on the northern regions associated to lentic ecosystems, main European rivers acting as ecological corridors for all freshwaters, and a mixed distribution of connectivity hotspots in southern and Mediterranean ecoregions, associated with lentic and/or lotic systems. Main Conclusions We showed an explicit connection between landscape structure and dispersal process at large geographic scales, highlighting hotspots of connectivity for the European waterscape. The spatial distribution of hotspots points to differences in landscape configurations potentially accounting for biogeographic diversity patterns and for mechanisms that have to be considered in conservation planning.
    Type of Medium: Online Resource
    ISSN: 1366-9516 , 1472-4642
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2020139-4
    detail.hit.zdb_id: 1443181-6
    SSG: 12
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  • 5
    In: Ecology and Evolution, Wiley, Vol. 12, No. 7 ( 2022-07)
    Abstract: An organism's body size plays an important role in ecological interactions such as predator–prey relationships. As predators are typically larger than their prey, this often leads to a strong positive relationship between body size and trophic position in aquatic ecosystems. The distribution of body sizes in a community can thus be an indicator of the strengths of predator–prey interactions. The aim of this study was to gain more insight into the relationship between fish body size distribution and trophic position in a wide range of European lakes. We used quantile regression to examine the relationship between fish species' trophic position and their log‐transformed maximum body mass for 48 fish species found in 235 European lakes. Subsequently, we examined whether the slopes of the continuous community size distributions, estimated by maximum likelihood, were predicted by trophic position, predator–prey mass ratio (PPMR), or abundance (number per unit effort) of fish communities in these lakes. We found a positive linear relationship between species' maximum body mass and average trophic position in fishes only for the 75% quantile, contrasting our expectation that species' trophic position systematically increases with maximum body mass for fish species in European lakes. Consequently, the size spectrum slope was not related to the average community trophic position, but there were negative effects of community PPMR and total fish abundance on the size spectrum slope. We conclude that predator–prey interactions likely do not contribute strongly to shaping community size distributions in these lakes.
    Type of Medium: Online Resource
    ISSN: 2045-7758 , 2045-7758
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 2635675-2
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  • 6
    In: Aquaculture, Fish and Fisheries, Wiley, Vol. 3, No. 3 ( 2023-06), p. 287-301
    Abstract: Traditionally, population sizes, ecology, and threats to species and their habitats have been obtained by empirical scientific studies. However, the knowledge of local and indigenous communities worldwide has been acknowledged as an extremely rich and underused source of information on how the environment, biodiversity, and local conditions are changing over time. In this view, the objective of the study was to investigate local fishers’ knowledge of local names, habitats, uses, market price, change in population abundance, and threats faced by the snakehead fish ( Parachanna obscura ) in Ivorian freshwaters. The study was conducted using face‐to‐face interviews and a structured questionnaire with 381 fishers during the period from October 2020 to February 2021. The results show that this fish species is strongly appreciated for the good taste of its flesh, with market prices varying between 1.5 and 3€ on average. All respondents confirmed that the species is not yet produced in aquaculture and mentioned their willingness to support its introduction into aquaculture. Several local names of P. obscura fish were recorded, with ‘Sounôgô‐djêguê’ (used in 36% of fishers’ ethnic groups), ‘Pino’ (21%), and ‘Édjoué‐bile’ (21%) being the most popular names used in Ivorian fishers’ communities. All respondents agreed that P. obscura is a potamodromous fish species living preferably in wetlands, rivers, lakes, and streams. A significant decrease in the abundance of this fish was observed by 71% of fishers, perceived mainly due to overfishing, deforestation around watersheds, habitat destruction/modification, obnoxious fishing practices, pesticide use in farms close to watersheds, and climate change, especially lack of rainfall. The study clearly demonstrated the importance of local ecological knowledge of fishers in identifying threats to fish populations, habitat types used by the species, and other relevant information; therefore, this ecological knowledge has to be integrated into biomonitoring and conservation policy of aquatic biodiversity. The information obtained from this study is also helpful for future studies on the management and cultivation of this species.
    Type of Medium: Online Resource
    ISSN: 2693-8847 , 2693-8847
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 3119348-1
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  • 7
    In: Ecology of Freshwater Fish, Wiley, Vol. 32, No. 4 ( 2023-10), p. 852-863
    Abstract: We investigated the relative influence of local environmental and spatial factors in structuring the community composition of fish at 15 sampling sites along the longitudinal gradient of the Lower Niger River Basin (LNRB) in dry and rainy seasons using distance‐based redundancy analysis and variation partitioning analysis. We collected a total of 3807 fish specimens representing 42 species. Our result indicated that the fish community composition differed between the upper and lower regions of the river. The communities in the upper region is influenced by high‐nutrient concentrations, while downstream sites were characterized by high concentrations of suspended solids. Variation partitioning revealed higher contributions of spatial than environmental predictors on fish community composition, with a higher total predicted variance in dry season. The variations in the community composition between upper and lower region may be attributable to the differences in the nature of anthropogenic activities within the regions, which influenced the local conditions differently. Differences in flow dynamics between upper and lower regions as attributable to black and white floods in the LNRB modify the connectivity between sites. Dispersal among sites may be more limited downstream than in the upper region, particularly in the dry season, because damming in the upper region also interrupts the natural flood regime such that there are low water levels in the lower region, which spatially isolate fish communities at certain sampling sites. The relatively higher total predicted variance during dry season may be attributable to the temporal differences in abiotic conditions between sites, which may have influenced site level community composition and abundance differently.
    Type of Medium: Online Resource
    ISSN: 0906-6691 , 1600-0633
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2028166-3
    SSG: 21,3
    SSG: 12
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  • 8
    In: Ecology and Evolution, Wiley, Vol. 13, No. 1 ( 2023-01)
    Abstract: An essential factor for aquatic conservation is genetic diversity or population divergence, which in natural populations reflects the interplay between geographical isolation with restricted gene flow and local evolution of populations. The long geological history of Africa may induce stronger among‐population divergence and lower within‐population divergence in fish populations of African watersheds. As an example, we studied population structure of the African snakehead fish Parachanna obscura. Our study aimed: (1) to develop a set of highly polymorphic microsatellite markers suitable for the analysis of genetic diversity among P. obscura and (2) to study the genetic diversity and structure of P. obscura populations from the West Africa region and mostly from Côte d'Ivoire, with respect to the effects of climate region and geographical distance on the genetic differentiation. A total of 259 specimens from 15 locations of P. obscura were collected over the West Africa region reflecting a high variability of pairwise geographical distances and variability of hydrological connectivity of the area. We developed a set of 21 polymorphic microsatellite markers for studying population genetics of the fish. The results showed relatively low intragenetic diversity for all the 15 locations, certainly attributable to confinement of fish in segregated catchments, resulting in limited gene flow. We also found evidence for local adaptation processes, suggested by five out of 21 microsatellite loci being under putative selection, according to BAYESCAN analysis. In turn, there was strong genetic differentiation ( F ST   〉  0.5) among fish from most locations, reflecting the allopatric development in watersheds without hydraulic connectivity. Neighbor‐joining dendrogram, Principal Coordinate Analysis, and analysis of ancestral groups by STRUCTURE suggested that the 15 locations can be divided into three clusters, mainly matching the dominant climate zones and the segregation of the watersheds in the region. The distinct genetic structure of the fish from the 15 locations obtained in this study suggests that conservation and sustainable management actions of this fish resource should avoid genetic mixing of potentially locally adapted populations.
    Type of Medium: Online Resource
    ISSN: 2045-7758 , 2045-7758
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2635675-2
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  • 9
    In: Global Ecology and Biogeography, Wiley, Vol. 30, No. 8 ( 2021-08), p. 1558-1571
    Abstract: We tested whether there is a strong effect of species interactions on assembly of local lake fish communities, in addition to environmental filters and dispersal. Location Seven hundred and seventy‐two European lakes and reservoirs. Time period 1993–2012. Major taxa studied Nineteen species of freshwater fishes. Methods We applied a latent variable approach using Bayesian Markov chain Monte Carlo algorithms (R package “BORAL”). We compared the contributions of six environmental predictors and the spatial organization of 772 European lakes in 209 river basins on the presence/absence of the 19 most frequent fish species and on the biomass and mean mass of the six dominant species. We inspected the residual correlation matrix for positive and negative correlations between species. Results Environmental (50%) and spatial (10%) predictors contributed to the presence/absence assembly of lake fish communities, whereas lake size and productivity contributed strongly to the biomass and mean mass structures. We found highly significant negative correlations between predator and prey fish species pairs in the presence/absence, biomass and mean mass datasets. There were more significantly positive than negative correlations between species pairs in all three datasets. In addition, unmeasured abiotic predictors might explain some of the correlations between species. Main conclusions Strong effects of species interactions on assembly of lake fish communities are very likely. We admit that our approach is of a correlational nature and does not generate mechanistic evidence that interactions strongly shape fish community structures; however, the results fit with present knowledge about the interactions between the most frequent fish species in European lakes and they support the assumption that, in particular, the mean masses of fish species in lakes are modified by species interactions.
    Type of Medium: Online Resource
    ISSN: 1466-822X , 1466-8238
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 1479787-2
    detail.hit.zdb_id: 2021283-5
    SSG: 12
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