Melanie Mueller

Taxonomic sufficiency in freshwater ecosystems: effects of taxonomic resolution, functional traits, and data transformation

Abstract.  Taxonomic sufficiency (TS) has been proposed for assessing community composition and environmental impacts as a way to balance the need to indicate the biology of the organisms present with time and effort needed for species identification. TS has been applied most often to marine and freshwater macroinvertebrates, but tests of its usefulness are lacking for other freshwater groups. We analyzed the effects of taxonomic resolution, functional groupings, and data transformation on multivariate community patterns in periphyton, macrophytes, macroinvertebrates, and fishes, and on the quantification of biodiversity and environmental gradients. The applicability of TS differed strongly among taxonomic groups, depending on the average taxonomic breadth of the species sets. Numerical data resolution had more pronounced effects on community patterns than taxonomic resolution. Richness was strongly affected by data aggregation, but diversity indices were statistically reliable up to order level. Taxonomic aggregation had no significant influence on ability to detect environmental gradients. Functional surrogates based on biological traits, such as feeding type, reproductive strategy, and trophic state, were strongly correlated (&rgr;  =  0.64–0.85) with taxonomic community composition. However, environmental correlations were generally lower with data aggregated to functional traits rather than to species. TS was universally applicable within taxonomic groups for different habitats in one biogeographic region. Aggregation to family or order was suitable for quantifying biodiversity and environmental gradients, but multivariate community analyses required finer resolution in fishes and macrophytes than in periphyton and macroinvertebrates. Sampling effort in environmental-impact studies and monitoring programs would be better invested in quantitative data and number of spatial and temporal replicates than in taxonomic detail.

Effects of sampling techniques on population assessment of invasive round goby Neogobius melanostomus

In this study, a comparison of point abundance sampling (PAS) electrofishing, angling with two different hook sizes and trap-based fishing was performed in a non-wadeable river to analyse their effects on catch per unit effort (CPUE) and population characteristics of invasive round goby Neogobius melanostomus. PAS electrofishing was identified as the most effective (mean ± s.e. CPUE = 57 ± 4 N. melanostomus min(-1) ) and least selective method in terms of size, feeding status and species composition. Angling had the second highest CPUE, but was more size selective and resulted in a higher proportion of males compared to electrofishing [overall sex ratio angling (female:male) = 1:0.92, electrofishing 1:0.65]. Owing to low CPUE (0.012 ± 0.004) and low frequency of occurrence, minnow traps were least suitable for N. melanostomus population assessment. The results of this study suggest that a higher degree of standardization and inter-calibration is useful to achieve better comparability of population data of invasive N. melanostomus and other benthic fish species.

The role of life history traits and habitat characteristics in the colonisation of a secondary floodplain by neobiota and indigenous macroinvertebrate species

Modification of streams and rivers has mediated range expansions of several species into areas beyond their natural distribution. In this study, a newly created secondary floodplain channel (SFC), with three connections to the Danube, was used as a model system to compare colonisation by indigenous versus non-indigenous species of macroinvertebrates. Three years after the opening of the channel, it was colonised by 210 taxa. Indigenous species were more abundant than non-indigenous ones, both in the channel as well as in the Danube, and colonisation was mostly determined by habitat characteristics. In non-indigenous species, proximity to the source habitat was the main explanatory variable. Non-indigenous colonisers mostly had indifferent functional traits, in contrast to indigenous macroinvertebrates. These differences were particularly pronounced in amphipods where an equal number of five species per group occurred. The results of this study suggest that the factors determining colonisation patterns of indigenous versus non-indigenous species with similar dispersal abilities can strongly differ. Consequently, the creation of specific habitat structures (gravel-dominated, high current flow, bank vegetation) in restoration of floodplain channels can increase competitiveness of native species valued in conservation, particularly if sufficiently long channels with limited edge effects to the source habitat are built.

A new tool for assessment and monitoring of community and ecosystem change based on multivariate abundance data integration from different taxonomic groups

BackgroundThe integrative assessment of responses to environmental disturbance simultaneously considering multiple taxonomic groups or guilds has become increasingly important in ecological monitoring. The most common solution to combine data of different taxonomic groups is the calculation of compound indices comprising several individual indicators. However, these indices run the risk of cancelling out underlying trends when single components change in different directions. In contrast, multivariate community analyses are supposed to be more sensitive to detect environmental responses, since information on the abundance of multiple species is not reduced to a single dimension.ResultsWe propose a new standardised approach for multivariate community analyses on ecosystem scale, based on a combined data matrix from different taxonomic groups. The power of these multivariate analyses is compared with two single score indices integrating data from all involved taxonomic groups (Ecological Quality Class according to the European Water Framework Directive and Shannon diversity). The multivariate indication of ecosystem change was much more sensitive and powerful in detecting and monitoring environmental impacts and restoration effects than single numeric score indices.ConclusionsCompared to common monitoring systems based on compound indices, the multivariate analysis of multiple taxonomic groups is feasible with the same sampling effort, and independent of the investigation scale and the occurrence of certain indicator taxa. Since ecological community data are structured similarly throughout freshwater, marine and terrestrial ecosystems, the presented methods for data combination and multivariate indication can be analogously applied in any other habitats and can improve data integration across ecosystem borders.

Fish injury and mortality at pumping stations: a comparison of conventional and fish-friendly pumps

Pumping of water during floods from hinterland drainage systems into the main river poses a health risk to fishes and comparative studies are crucial to identify the most fish-friendly pump designs and operations. We investigated the effects on fish health of pump passages through four conventional and one ‘fish-friendly’ pump. All pump types caused external fish injuries leading to direct and delayed mortality. Immediate mortality and injury intensity increased with revolutions per minute (rpm) and differed significantly (P<0.05) between pump types. At the ‘fish-friendly’ Pentair pump (Fairbanks Nijhuis, London, UK), higher numbers of injuries resulting from blunt force (e.g. haemorrhage, scale loss and fin tears) were detected than at the conventional pumps, potentially due to the differences in blade design. The Koster pump (Koster, Heide, Germany) at low rpm proved to be similarly fish friendly as the specially developed fish-friendly Pentair pump due to the low number of entrained fishes. As a measure to reduce potential damaging to fishes, the pumps should run on low rpm as often as possible. This lowers the risk of collision with machine parts and hence mortality rate, as well as the suction effects see at high rpm. After long periods in an anergic state, pumps should generally run on low rpm before changing to higher rates.

Physical and hydraulic forces experienced by fish passing through three different low-head hydropower turbines

Knowing the kinds of physical stress experienced by fish passing through hydropower turbines can help optimise technologies and improve fish passage. This paper assesses the hydraulic conditions experienced through three different low-head turbines (a very low head (VLH), Archimedes screw and horizontal Kaplan turbine), taken using an autonomous sensor. In total, 127 Sensor Fish deployments were undertaken across all three turbines, generating 82 valid datasets. Decompression was rare at the VLH and screw turbines and rarely fell more than 10kPa below atmospheric pressure. In contrast, the Kaplan was capable of generating pressures as low as 55.5kPa (~45kPa below atmospheric pressure), over shorter periods of time. More severe ratios of pressure changes could, therefore, be expected for both surface- and depth-acclimated fish at the Kaplan than at the other turbines. Strike was another possible source of fish injury (detected in 69–100% of deployments), and although strike severity was highest at the Kaplan, strike was more likely to be encountered at the screw and VLH than the Kaplan turbine. Shear occurred only near the blades of the Kaplan, and not at severe levels. The results demonstrated that low-head hydropower facilities are not without their risks for downstream migrating fish.

Comparison of nine different methods to assess fish communities in lentic flood‐plain habitats

This study compares the effectiveness and representativeness of electrofishing, snorkelling, seining, baited lift netting, multi-mesh gillnetting, baited fish traps, fyke netting, angling and longline fishing, considering three typical lentic flood-plain habitats at different times of day. Electrofishing was by far the most effective method yielding highest species richness, species trait representation and catch per unit of effort (CPUE), followed by seining. For single species like dace Leuciscus leuciscus, European ruffe Gymnocephalus cernua, common bream Abramis brama and silver bream Blicca bjoerkna, seining was more effective than electrofishing. With both methods, some species were more consistently caught during night, dusk or dawn than during daylight. All other methods tested cannot be generally recommended for fish community assessments in shallow backwaters due to their low representativeness of species inventory and generally low CPUE. Based on these results, electrofishing of 30 m transect replicates at different times of day for monitoring the fish community in shallow backwaters, can be recommended, enabling the maximum possible comparability to adjacent river habitats. Seining should be considered as an alternative if accessibility of habitats is restricted or electrofishing is prohibited. The 25 species detected in the backwaters also suggest that these habitats contribute a large proportion of fish diversity and should be included in standard assessments of river ecological status.