Session B5: The Danube Fish Bypass System of Vienna/Freudenau and its Importance as a Lifecycle Habitat

Abstract: For the fish bypass at the Danubehydropower station Wien/Freudenau the functioning as migration facility has been classified as functional after construction in 1997. The importance of habitat support for the lifecycles of Danube fish species becomes clearly visible in times when degraded, impounded, current speed reduced section of the river are dominating the fluvial ecosystem. Central parts of impounded areas are not supporting all the needs of riverine fish: Gravel-spawning grounds, suitable flow velocity and diverse 0+ fish habitats are missing. Upper most part of impoundments, tributaries and artificial rivers, like fish bypass systems, can function as essentially needed last habitats. The fish bypass system of Wien/Freudenau has a length of 1.6 km and a discharge of at least 1.5 m³. 2/3 of the system has been constructed as a near-natural circumvention stream and 1/3 as a nature-like pool pass. After 15 years of operation it becomes clearly visible that fish use the bypass system as spawning ground extensively and therefore it can make an important contribution for the maintenance of several endangered species, like the nase (Chondrostoma nasus) and the barbel (Barbus barbus). In the present study a monitoring was conducted throughout a year. Seasonal changes in abundances, species diversity and spawning events were observed. A total of 35 species colonize the bypass with temporary and spatial fluctuations. In early spring (February and March), the indicator species of the free flowing Danube, nase and barbel, migrated into the fish pass in very high quantities. After spawning in April and May the adults disappeared and a few weeks later thousands of young-of-theyear were observed. The present data show, that the chosen natural like solution of a bypass system serves in contrast to a hard technical construction, - additionally to its migration function - like a Danube tributary of the grayling zone. 23 species of young-of-theyear fish classes’ inhabited the system in 2014. Some of them have been proved in larval stages by barcoding

RECENT DATA ON THE DISTRIBUTION OF FRESHWATER ICHTHYOFAUNA IN ALBANIA

U ovom članku izložen je ažurirani popis slatkovodnih riba u Albaniji za svaki podsliv. Prikazani podaci o rasprostranjenosti i popisi taksona temelje se na pregledu literature do listopada 2022. i intenzivnom terenskom radu u posljednjih 15 godina. Prikazani su podaci o distribuciji 101 vrste riba (koje potječu iz 25 porodica) iz 11 različitih podslivova. Postoje novi zapisi koji uključuju domaće, strane i translocirane vrste riba. Osobitost albanskih slatkovodnih riba je istaknuta pri definiranju specifične ihtiološke regije za cijelu balkansku regiju. Fauna slatkovodnih riba Albanije predstavlja posebnu vrijednost nacionalne baštine, posebice zbog svoje raznolikosti i visokog stupnja endemičnosti. To je uglavnom zbog složenih geoloških i klimatskih uvjeta i položaja između Jadranskog i Jonskog mora na zapadu i kontinentalnih područja Balkana s druge strane, što je omogućilo različite kolonizacije izvan područja i duga razdoblja specijacije. Jedanaest hidrografskih bazenskih jedinica analizirano je u pogledu sastava vrsta, evolucijskih obrazaca i ekoloških značajki. Ovim pregledom broj albanskih slatkovodnih riba iznosi 101, s 20 vrsta dodanih iz prethodnog popisa iz 1995. godine i nekoliko vrsta izbrisanih zbog taksonomskih promjena.In this article, we provide an updated list of freshwater fishes in Albania for each sub-basin. The distribution data and taxa-lists presented are based on a literature review up to October 2022 and intensive fieldwork conducted in the last 15 years. Distributional records of 101 fish species (deriving from 25 families) in 11 different sub-basins are reported. There are new records that include native, alien and translocated fish species. The distinctiveness of Albanian freshwater fishes is highlighted while defining a specific ichthyological region for the whole Balkan region. The freshwater fish fauna of Albania represents a special value of the national heritage, especially due to its diversity and a high degree of endemicity. This is mainly due to the complex geological and climatic conditions, and the location between the Adriatic and Ionian Seas on the west and the continental areas of the Balkans on the other side, which have allowed different colonization from outside the area and long periods of speciation. Eleven hydrographic basin units are analyzed for species composition, evolutionary patterns, and ecological features. This review brings the number of Albanian freshwater fish taxa to 101, with 20 species added from the previous 1995 inventory and several species deleted due to taxonomic changes

Does soundpeaking affect the behavior of chub (Squalius cephalus) and brown trout (Salmo trutta)? : an experimental approach

Increased turbulent flow and sediment transport during flood or hydropeaking events often induces rapid changes in underwater sound pressure levels, which is here referred to as soundpeaking. This study is the first to investigate such a change in the underwater soundscape in relation to fish behavior using an experimental approach. Trials were conducted in an experimental channel stocked with either adult chub (Squalius cephalus) or brown trout (Salmo trutta). To mimic soundpeaking, the underwater soundscape of a small alpine river was recorded during a flood event and later played back through an underwater speaker during treatment trials. Furthermore, trials were recorded with a video camera, and based on the fish position, movement variables (swimming distance, number of movement direction changes, variance of the acceleration), the aggregation of individuals, the longitudinal and the lateral position in the experimental area were compared between control (no sound played) and treatment trials. During treatment trials, brown trout changed their movement direction significantly more often, chub showed a significantly higher variation of the acceleration, and individuals from both species were significantly more aggregated. Furthermore, the soundpeaking treatment had a significant effect on the longitudinal position of brown trout in the experimental area. However, the overall results did not provide any indication for a stronger soundpeaking effect in chub despite being equipped with much more refined hearing abilities in comparison to brown trout. Based on these results and findings from other studies, soundpeaking is discussed as a behavioral trigger as well as a source of acoustic stress

The Vjosa River corridor: a model of natural hydro-morphodynamics and a hotspot of highly threatened ecosystems of European significance

Context: Large near-natural rivers have become rare in Europe, a fact reflected in the high conservation status of many riverine ecosystems. While the Balkan still harbors several intact river corridors, most of these are under pressure from planned hydropower constructions. Unfortunately, there is little information available on the hydromorphodynamics and biota of Balkan rivers under threat. Objectives: We present a synthesis of research on the Vjosa in Southern Albania. Here, longitudinal continuity in water flow, undisturbed sediment transport and intact fluvial dynamics are still maintained, but threatened by two large dams planned in its downstream section. We intend to provide a first multidisciplinary inventory of this river system as an example of the knowledge base required for sound water management decisions in the Balkans. Methods: Based on field work of a multidisciplinary consortium of scientists from Albania and other countries conducted from 2017 onwards, we summarize the most important findings on geomorphology of the riverine landscape, habitat turnover rates, vegetation ecology and selected animal taxa. Results: We found evidence that significant areas (86%) of the river corridor are covered by habitats listed in Annex 1 of the European Union Habitats Directive. These are associated with a high number of threatened biota. Conclusions: Our findings underscore the value of the Vjosa as one of the few remaining reference sites for dynamic floodplains in Europe and as a natural laboratory for interdisciplinary research. We emphasize that such multidisciplinary studies are a prerequisite for informed evaluation of potential impacts caused by hydropower plants

Sturgeons in large rivers: detecting the near‑extinct needles in a haystack via eDNA metabarcoding from water samples

Sturgeon populations are declining worldwide and are the target of extensive conservation efforts. Addressed in several pieces of legislation, sturgeons have received considerable attention as flagship or umbrella species. Despite the need for a better understanding of the distribution and population status, the use of traditional sampling methods failed in the past, thereby hampering reliable assessments, a prerequisite for conservation. Here, we describe the development and application of an environmental DNA (eDNA) metabarcoding approach for detecting rare sturgeons in large rivers. Exemplarily, we developed a reference database for five native Danube sturgeons (Acipenser stellatus, Acipenser gueldenstaedtii, Acipenser ruthenus, Acipenser nudiventris, and Huso huso) and two nonnative species (Acipenser baerii and Acipenser transmontanus), assessed these ex situ, and used eDNA as a detection tool along the entire length of the Danube (Europe, ~ 2850 km) and major tributaries. In ex situ analyses, all assays yielded positive amplifications for the assessed sturgeon species. In the Danube, the presence of A. ruthenus was confirmed at 14 of 29 sites (48.3%), and in 2 of 18 tributary sites (11.1%), providing the first comprehensive large-scale biogeographical snapshot of this species. Relative number of reads assigned to A. ruthenus varied between 0 and 2.5%, with sites registering positive detections being clustered in 3 sections of the Danube. Our findings enabled us to confirm the advantages of eDNA monitoring over traditional sampling methods for comprehensive whole-river snapshot studies of sturgeons conducted on a large geographical scale, and therefore we consider it to be a promising approach for application in conservation measures, fisheries management, scientific studies, and adaptive management plans for sturgeons on a global scale

Longitudinal river zonation in the tropics: examples of fish and caddisflies from endorheic Awash river, Ethiopia

Primary Research PaperSpecific concepts of fluvial ecology are well studied in riverine ecosystems of the temperate zone but poorly investigated in the Afrotropical region. Hence, we examined the longitudinal zonation of fish and adult caddisfly (Trichoptera) assemblages in the endorheic Awash River (1,250 km in length), Ethiopia. We expected that species assemblages are structured along environmental gradients, reflecting the pattern of large-scale freshwater ecoregions. We applied multivariate statistical methods to test for differences in spatial species assemblage structure and identified characteristic taxa of the observed biocoenoses by indicator species analyses. Fish and caddisfly assemblages were clustered into highland and lowland communities, following the freshwater ecoregions, but separated by an ecotone with highest biodiversity. Moreover, the caddisfly results suggest separating the heterogeneous highlands into a forested and a deforested zone. Surprisingly, the Awash drainage is rather species-poor: only 11 fish (1 endemic, 2 introduced) and 28 caddisfly species (8 new records for Ethiopia) were recorded from the mainstem and its major tributaries. Nevertheless, specialized species characterize the highland forests, whereas the lowlands primarily host geographically widely distributed species. This study showed that a combined approach of fish and caddisflies is a suitable method for assessing regional characteristics of fluvial ecosystems in the tropicsinfo:eu-repo/semantics/publishedVersio

Grasping Kinematics from the Perspective of the Individual Digits: A Modelling Study

Grasping is a prototype of human motor coordination. Nevertheless, it is not known what determines the typical movement patterns of grasping. One way to approach this issue is by building models. We developed a model based on the movements of the individual digits. In our model the following objectives were taken into account for each digit: move smoothly to the preselected goal position on the object without hitting other surfaces, arrive at about the same time as the other digit and never move too far from the other digit. These objectives were implemented by regarding the tips of the digits as point masses with a spring between them, each attracted to its goal position and repelled from objects' surfaces. Their movements were damped. Using a single set of parameters, our model can reproduce a wider variety of experimental findings than any previous model of grasping. Apart from reproducing known effects (even the angles under which digits approach trapezoidal objects' surfaces, which no other model can explain), our model predicted that the increase in maximum grip aperture with object size should be greater for blocks than for cylinders. A survey of the literature shows that this is indeed how humans behave. The model can also adequately predict how single digit pointing movements are made. This supports the idea that grasping kinematics follow from the movements of the individual digits

Transformatie van monofunctionele kantoorlocaties

Omstreeks 2002 was er een kentering op de Nederlandse kantorenmarkt zichtbaar. Waar in het verleden de Nederlandse kantorenmarkt vooral door uitbreiding werd gedreven, is er sinds 2002 sprake van een vervangingsmarkt. Vraag en aanbod zijn in de huidige markt niet meer in evenwicht en waar voorheen leegstand vooral cyclisch werd gedreven is er op dit moment sprake van een structureel overaanbod aan kantoren. De leegstand is in Nederland reeds opgelopen tot 14,1 procent. (DTZ, 2012) Van deze leegstand is ongeveer een derde van structurele aard (>drie jaar). De kans op wederverhuur voor een aanzienlijk deel van dit (structurele) overschot aan kantoren is zeer klein

New data on Garra makiensis (Cyprinidae, Labeoinae) from the Awash River (Ethiopia) with remarks on its relationships to congeners on the Arabian Peninsula

On the African continent, the genus Garra consists of several species often insufficiently separated from each other by diagnostic characters. Herein, a detailed morphological redescription of Garra makiensis from the Awash River drainage is presented, together with additional data on the type specimens of G. makiensis and G. rothschildi. Mitochondrial CO1 sequence data are also provided, including the historic paralectotype of G. makiensis, with a comparison to Garra species from Africa and the Middle East. Based on these sequences, G. makiensis clusters outside the group of African congeners and is a sister lineage to species from the south-east of the Arabian Peninsula. Although morphologically variable, G. makiensis is characterised by having a single unbranched pectoral-fin ray, a short distance between vent and anal-fin origin (7.3–19.7 % of pelvic – anal distance), chest and belly covered with scales, and a prominent axillary scale at base of pelvic fin (18.8–35.5 % of pelvic-fin length)

Growth and Nutrient Removal Efficiency of Sweet Wormwood (<i>Artemisia annua</i>) in a Recirculating Aquaculture System for Nile Tilapia (<i>Oreochromis niloticus</i>)

The maintenance of optimal water quality for fish production is one of the major challenges in aquaculture. Aquaponic systems can improve the quality of water for fish by removing the undesirable wastes and in turn produce a second marketable crop. However, there is no information on the growth and nutrient removal capability of Artemisia annua in aquaponic systems. This study evaluated the effect of plant density on water quality, the growth of A. annua and Oreochromis niloticus in a small scale aquaponic system in Kenya. The aquaponic system consisted of three treatments representing different plant densities (D1: 48 plants/m2, D2: 24 plants/m2 and D3:0 plants/m2). The high plant density system contributed significantly (p &lt; 0.05) to the removal of all nutrients. The removal efficiency of ammonia was significantly higher in D1 (64.1 &#177; 14.7%) than in D2 (44.5 &#177; 6.8%) and D3 (38.0 &#177; 12.1%). Nitrates and nitrites were inconsistent, whereas phosphorus increased gradually in all treatments. The productivity of plants was higher in D1 than D2. Fish growth rates were significantly higher in D1 (0.35 &#177; 0.03 g/d) and D2 (0.32 &#177; 0.02 g/d) than in D3 (0.22 &#177; 0.04 g/d). The results show that A. annua can be cultivated in aquaponic systems due to its nitrogen removal capabilities