Hydro-morphological stressors reduce distribution range and affect population status of cyprinid fishes in Austria

Abstract

Rivers worldwide have been transformed into fragmented, impounded, channelized, and flow-regulated ecosystems. These anthropogenic transformations can reduce fish distribution and population status, especially of those species belonging to medium- or long-distance migratory guilds and those dependent on free-flowing rivers and intact sediment and habitat conditions. Here, we aim to understand how different hydro-morphological pressure types affect the distribution and population status of key potamodromous fish species of the rheophilic and lithophilic fish guilds, the barbel (Barbus barbus) and the nase (Chondrostoma nasus). We also assess the status of chub (Squalius cephalus) to include a species less sensitive to habitat degradation. For the first time, we assembled an extensive Austrian-wide GIS-based fish sampling database with hundreds of biological surveys, allowing us to analyze quantitatively >4,000 river kilometers for presence/absence of target fishes and to assess population status. The data reveal that the distribution range of target species decreased by around 40–60% compared to their natural ranges according to the reference standard (Leitbild). Hydro-morphological pressures affect target species’ population biomass, and trends between impact types can be detected. Chub and barbel exhibit the highest median biomass in free-flowing rivers and residual flow reaches, followed by reservoir sections. Of all pressure types, population biomass is lowest in hydropeaked river stretches. Nase biomass has a grand median of 0.0 kg/ha across all sites, showing hardly any differences between hydro-morphological pressure types. Overall, our results show a drastic shrinkage of the distribution range of three cyprinid fish species previously prominent in Austria. By linking current population vitality to hydro-morphological stressors and ecological status assessments, this study sets a baseline for data-based conservation actions of (Red-listed) species as well as policy and management frameworks.

Variation in hydropeaking‐induced stranding of Barbus barbus L. and Chondrostoma nasus L. larvae: Assessing the impact of daytime and down‐ramping rates

“…These negative cause-effect patterns also pertain to previously widespread species, such as the common barbel (Barbus barbus L.) and the common nase (Chondrostoma nasus L.) (Hayes, Schaufler, et al, 2022;Penczak & Kruk, 2000), which inhabit rivers throughout Europe (Kotlík & Berrebi, 2001;Kottelat & Freyhof, 2007) and are excellent indicators of hydro-morphological conditions and river integrity (Britton & Pegg, 2011;Chovanec et al, 2003;Melcher & Schmutz, 2010;Schiemer et al, 2002). Although their ecology is similar, it differs in some ways, for example, the timing of early juvenile development.…”

Integrating Open-Source Datasets to Analyze the Transboundary Water–Food–Energy–Climate Nexus in Central Asia

“…Degraded ecosystems often have reduced biodiversity and may no longer provide fundamental services, so conservation and restoration efforts are imperative [107,108]. In this regard, geodata provide the fundamental information needed to assess the ecological status quo [109][110][111] and, based thereupon, derive prioritization frameworks for conservation and restoration [112,113] at various spatial levels [114]. To this aim, Table 6 presents key data related to freshwater ecology.…”

Cold thermopeaking-induced drift of nase Chondrostoma nasus larvae

“…In this study, we evaluated the impact of hydropeaking and cold thermopeaking on larvae of nase Chondrostoma nasus (L.), a cypriniform species for the conservation of European rivers, whose populations have been declining in the last several decades (Jurajda 1995 ; Schiemer et al. 2002 ; Hayes et al 2022b ). We performed flume experiments in an outdoor semi-natural stream facility to assess whether cold thermopeaking could lead to a higher fish drift than hydropeaking without temperature changes.…”