Search

Copyright of Canadian Journal of Fisheries & Aquatic Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Fisheries & Aquatic Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Fisheries & Aquatic Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Nature-based solutions (NBS) are increasingly suggested to address biodiversity decline and climate change. However, many ecosystems are hardly used as NBS, including ponds and pondscapes. We therefore examine how policies and practices affect their implementation as NBS. Using a content analysis of policy documents and stakeholder inputs, we assess the policy context in eight countries but also zoom in on policies and practices in seventeen pondscapes. We derive three key insights: first, a protective status for a pond or pondscape interlinks with other enabling factors for NBS implementation, and protection and conservation should therefore be considered more often as NBS. Second, there is a shortage of, especially long-term, financing. Third, local leadership should be nurtured to overcome a lack of institutional cooperation and stakeholder awareness as well as fragmented land ownership. Beyond that, we show that implementation barriers interlink and interventions should therefore address several barriers simultaneously. [ABSTRACT FROM AUTHOR]

Transformation of the natural land cover is one of the most important global changes. Changes in land use may strongly affect ecosystem functions and biodiversity by directly or indirectly modifying key structural properties. Here, we examined the effects of land use on the size structure of fish communities in subtropical Uruguayan streams. We analysed the suitability of non-taxonomic, size-related variables as a tool to elucidate shifts in stream fish assemblages along a gradient in land use change. We also tested some taxonomic variables (e.g., species richness and species diversity) to compare their response with size-related variables. In the more anthropogenic disturbed basins (i.e., dominance of urban and agricultural land use), we found higher size diversity, slope of size spectrum (flatter slopes) and total range of fish length, whereas higher species richness, fish abundance and species diversity were detected in more pristine stream basins (i.e., dominance of rangelands). In combination with traditional taxonomic variables, size-related variables of fish communities in streams may be effective tools in evaluating the changes occurring in freshwater ecosystems associated with anthropogenic changes in land use. [ABSTRACT FROM AUTHOR]

Planktivorous and benthivorous fish have been documented to influence the density and size structure of their prey communities in lakes. We hypothesized that piscivorous fish modify their prey fish communities in the same way and sought to find evidence for such predation effects from a comparison across 356 lakes located in nine European ecoregions. We categorized individual fish as being piscivore, nonpiscivore, or prey of piscivores, depending on species and individual size. We calculated piscivore, nonpiscivore, and piscivore prey densities, respectively, and fit linear abundance size spectra (SS) on lake-specific piscivore, nonpiscivore, and piscivore-prey size distributions. Multiple linear regressions were calculated to quantify the effect of piscivore density and SS slopes on nonpiscivore and piscivore-prey densities and SS slopes by accounting for potentially confounding factors arising from lake morphometry, productivity, and local air temperature. Piscivore density correlated positively with piscivore-prey density but was uncorrelated with density of nonpiscivores. Across a subset of 76 lakes for which SS slopes of piscivores were statistically significant, SS slopes of piscivores were uncorrelated with SS slopes of either nonpiscivores or piscivore prey. However, densities of piscivores, nonpiscivores, or piscivore prey were a significant negative predictor of SS slopes of the respective groups. Our analyses suggest that direct predation effects by piscivorous fish on density and size structure of prey fish communities are weak in European lakes, likely caused by low predator-prey size ratios and the resulting size refuges for prey fish. In contrast, competition may substantially contribute to between-lake variability in fish density and size. [ABSTRACT FROM AUTHOR]

We studied fish size structure by using mean size, size diversity, and the slope of linear size spectra of six common European fish species along large-scale environmental gradients. We further analyzed the response of these three size metrics to environmental variables and to density-dependent effects, i.e., relative estimates of abundance (catch per unit effort, CPUE). We found differences in the strength of main predictors of size structure between the six species, but the direction of the response was relatively similar and consistent for most of the size metrics. Mean body size was negatively related to temperature for perch ( Perca fluviatilis), roach ( Rutilus rutilus), and ruffe ( Gymnocephalus cernuus). Lake productivity (expressed as total phosphorus concentration) and lake depth were also predictors of size structure for four of six species. Moreover, we found a strong density dependence of size structure for all species, resulting in lower mean body size and size diversity and steeper size spectra slopes when density dependence increases. This suggests that density dependence is a key driver of fish size structure. [ABSTRACT FROM AUTHOR]