1,720,982 research outputs found
Biological and ecological data on an established rainbow trout (Oncorhynchus mykiss) population in an Italian stream
No full textTrophic preferences of three allochthonous fishes in Bormida River (Alessandria, NW Italy)
No full textThe introduction of alien species is currently one of the greatest threats to biodiversity conservation. This is particularly
true in river systems, where in recent years the growth of allochtonous or non-native species has increased dramatically.
Numerous studies have investigated the presence and the distribution of invasive species, but few focused on
the trophic habits of fish species introduced into new lotic environments. This paper provides information on the diet
of three alien species in the Bormida River, a lotic system previously altered by chemical pollution. Barbus barbus
shows a wide trophic spectrum, feeding mostly on benthic invertebrates but also consuming terrestrial arthropods,
coarse particulate organic matter, filamentous algae and, more rarely, fish. Feeding activity of Pseudorasbora parva
was mostly based on aquatic invertebrates but also algae and fine particulate organic matter was frequently ingested.
Regarding diet analysis of Rhodeus amarus, fine detritus and algae were the most important components in the examined
guts. There are significant potential overlaps with the trophic spectrum of native species
Artificial light at night affects fish passage rates in two small-sized Cypriniformes fish
Full text linkAn increasing presence of instream structures such as weirs, dams, culverts and reservoirs degrades habitats, fragments rivers and blocks fish movements worldwide. Longitudinal river movements are fundamental for many fish species and the most widespread solution to restore longitudinal connectivity is the implementation of different fish passage solutions. Fishway functionality, however, is highly variable. To design a functional fishway, several aspects of the fish's interaction with its environment need to be taken into consideration. Artificial light at night (ALAN) can affect a range of different behaviours in fish, from activity and movement to feeding and predator-prey relationships. In a fish passage setting, fish are exposed to artificial light at night (ALAN) in the form of light pollution, but, sometimes, also as part of the fish passage solution. Although likely highly species specific, the effect of artificial light on fish passage behaviour has been little explored. Here we study the passage behaviour of two small-sized fish species, European gudgeon (Gobio gobio) and Italian riffle dace (Telestes muticellus), over a scaled deep side notch weir in a hydraulic flume in three different light conditions: daylight, darkness and ALAN. Although both species passed the obstacle at high efficiencies under all light conditions, their passage behaviours were influenced by light, particularly at the higher levels. While ALAN reduced passage success and resulted in delayed passage for gudgeon, riffle dace passed at higher rates under the artificial light compared to night treatment. Both results indicate a risk of negative effects from ALAN on passage performance at real fishways or movement rates in lit areas of natural streams for both species. Independent of light conditions, individuals of both species also passed faster after repeated trials, demonstrating learning in a fish passage context
Taxonomic and functional responses of macroinvertebrate communities to dam construction in a non-wadeable river
No full textDamming and impoundment are among the main flow-related alterations in rivers worldwide. However, compared to the highland river sections where the impacts associated with dams have been largely studied, still scarce evidence is available in scientific literature for large, lowland rivers. In this study, the ecological effects of a hydropower dam in the Po River (Italy) on the taxonomic and functional responses of benthic macroinvertebrates were examined by comparing one station upstream of the dam with one downstream station over a six-year period. Weak and not significant differences were observed for taxon richness, abundance and community composition. By contrast, community-level proportion of macroinvertebrates associated with water velocity increased during medium and high flow condition and decreased during low flow condition in downstream stations. Such differences were also mirrored by the Flow-T index, that is a biomonitoring index recently developed to assess hydraulic conditions in rivers. Results of this study support the adoption of stressor-specific metrics in river biomonitoring
Individual activity levels and presence of conspecifics affect fish passage rates over an in-flume barrier
Full text linkDams and other in-stream obstacles disrupt longitudinal connectivity and hinder fish from moving between habitats. Fishways and other fish passage solutions are used to pass fish over these artificial migration barriers. Fish passage functionality, however, varies greatly with fish passage design and environmental conditions and depends on fish species and characteristics. In particular, swimming performance and fish behaviour are considered key characteristics to predict fish passage performance. It is also well known, but not well quantified, that the presence of conspecifics affects fish passage behaviour. In this study, we quantified individual passage rates of PIT-tagged gudgeons (Gobio gobio) over a scaled deep side notch weir in an hydraulic flume. We then quantified individual swimming capability (time to fatigue) and activity level (distance moved in an open field test) for the same individual fish and tested for potential effects on fish passage rate. To check for potential group effects, we then repeated the passage experiment for fish individually or in groups of five. More active fish displayed higher passage rates compared to less active fish, and fish passed the obstacle at higher rates in groups of five compared to alone. No effect of fish swimming capability on passage rates was detected. This result highlights the need to take both individual variation as well as the presence and behaviour of conspecifics into account in fish passage studies and evaluations. Doing so has the potential to improve the understanding of fish behaviour, and in the end, the design of fish passage solutions. Future studies should explore these results on free ranging fish and in relation to in-situ fish passage solutions
Survival and swimming performance in small-sized South European Cypriniformes tagged with passive integrated transponders
Full text linkA fundamental assumption in animal telemetry is that the behavior and performance of tagged animals do not substantially deviate from that of untagged animals. For fish, swimming behavior is fundamental for every part of a fish post-hatch life, influencing predator-prey interactions, movement ecology, and habitat choice. Here, we study the effects of PIT-tagging on survival and a range of swimming behaviors for South European nase (Protochondrostoma genei) and brook barbel (Barbus caninus), two small-sized, stream-dwelling cypriniforms native to the Italian peninsula. Effects on volitional swimming activity (sustained swimming) and maximum swimming speed (escape response; burst swimming) were tested in arena trials. Tagging effects on the prolonged swimming performance were tested in South European nase in an increasing velocity time-to-fatigue test, while a barrier passage test was designed to further investigate tagging effects in brook barbel. Both species displayed very high survival (95–100%), with no difference between tagged and control fish. No fish lost a tag during the 64 days of the study, and no tagging effect on swimming activity, prolonged swimming performance, barrier passage rate, or escape response was detected. Our results indicate that PIT-telemetry is a suitable tool to study the tested fish species
Stato di autoctonia e conservazione del genere Barbus dell’Adriatico settentrionale: dati di sequenza MTDNA e di microsatelliti nucleari rivelano tracce genetiche native, esotiche ed ibride
No full textL'ittiofauna dulcacquicola del Bacino dell'Adriatico Settentrionale è particolarmente ricca di endemismi. Questo insieme unico di specie è però attualmente ad alto rischio per effetto dell'ibridazione, conseguente alle pratiche di immissione. Una conclamata tendenza negativa è stata registrata per la maggior parte dei salmonidi nativi (ad es. trota fario, trota marmorata e temolo europeo) così come per il genere Esox, taxa di rilevante importanza economica e quindi fortemente gestiti dall'uomo. Tuttavia, recenti indagini ittiologiche hanno evidenziato come il problema di contatti secondari mediati dall'uomo sia sempre più rilevante anche per i più trascurati ciprinidi, tra cui le specie di barbo italiane (Barbus plebejus e B. caninus). Infatti, mentre fino al 1980 queste specie native erano riportate come ampiamente distribuite entro il Bacino Adriatico Settentrionale, in assenza dei congenerici trans-alpini, una rapida diffusione di B. barbus e il declino delle specie autoctone di barbo sono stati documentati negli ultimi due decenni. Tuttavia, i dati ittiologici ad oggi disponibili sono basati solamente su criteri morfologici piuttosto vaghi mentre informazioni genetiche molecolari sono generalmente assenti. Sono qui presentati alcuni dati di sequenza del DNA mitocondriale (citocromo b) e dati genotipici nucleari (microsatellite) di popolazioni di barbo provenienti da numerosi sistemi idrici del Bacino del paleo-Po. Complessivamente, sono stati individuati aplotipi mitocondriali riferibili sia ai nativi B. plebejus e B. caninus, sia all'alloctono B. barbus. I pattern di distribuzione delle varianti genetiche delle diverse specie sono estremamente diversi, con una massiva prevalenza di aplotipi esotici (B. barbus) nel corso principale del Fiume Po e nei tratti bassi dei suoi affluenti, e una prevalenza delle varianti genetiche di B. plebejus e B. caninus nei tratti alti e medi degli affluenti del Po e una presenza esclusiva delle stesse nei sistemi idrici di Adige, Brenta, Sarca e Reno. Dati microsatellite preliminari confermano i risultati mitocondriali e suggeriscono diversi scenari di introgressione in fiumi differenti: dall'assenza totale di introgressione, a una limitata ibridazione, fino alla completa sostituzione della forma nativa con quella esotica. Considerato il preoccupante stato di conservazione delle varie popolazioni di barbo qui analizzate, sono auspicabili immediate misure di gestione al fine di prevenire un'ulteriore compromissione delle popolazioni native di Barbo nel Bacino Nord Adriatico
Changes in fish assemblages of a previously highly polluted river: The role of environmental recovery and alien fish invasion in the Bormida River (Italy)
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