Brown trout Research Papers - Academia.edu (original) (raw)

2025, Aquaculture

Results of short-term experiments revealed that Arctic charr, Salvelinus alpinus, may take a substantial proportion of their food from the bottom, both under light and dark conditions. Longer term studies showed that charr required access to food on the bottom in order to maintain high rates of feed intake and growth. Fish appeared unable to adapt to taking food exclusively in the water column since food intake of fish prevented from feeding on the bottom remained low throughout the 17-week experiment.

2025

The marble trout Salmo marmoratus has been analyzed in a section of the Brenta River, where its populations show constant decrease despite many restocking operations carried out in the area. The study was carried out from October 2016 to December 2017 within three stream stretches placed from the border between Veneto and Trentino Alto Adige regions to the area near the Cismon del Grappa town. Analyses regarded fish communities, habitat availability for Salmo marmoratus, ecological status, fluvial functionality and chemical-physical features. Results highlighted several critical issues for the presence of well-structured marble trout populations, such as hybridization with brown trout Salmo trutta, habitat alteration and water pollution. Within the investigated area, pure Salmo marmoratus specimens (frequencies equal to 4-25%) and hybrids with Salmo trutta (5-27%) were observed. Brown trout was largely present in the area (8-60%). Available habitat ranged from 0 to 21% of the river ...

2025, River Research and Applications

Downstream migration of immature salmonids (smolts) may be associated with severe mortalities in anthropogenically altered channels. In Pacific salmon, several investigations have suggested the use of the dominating surface orientation of smolts to improve fish by-pass structures in large and deep hydroelectric reservoirs. The present study tested the use of a surface orientated travelling screen to guide Atlantic salmon (Salmo salar L.) and brown trout (Salmo trutta L.) smolts past a water abstraction site in a shallow lowland stream. The percentage of total discharge abstracted from the stream was included in the analyses. Indigenous migrating smolts were trapped, PIT tagged and subsequently released upstream of the water abstraction site. Releases shifted between a present or absent travelling screen. The migration success of the released smolts was evaluated using a trap situated downstream of the water abstraction site. There was no evidence that the surface oriented travelling screen had any influence on the probability of fish passing the water abstraction site. However, for both species, the probability of successful migration past the water abstraction site correlated negatively with the abstracted percentage of the total daily stream discharge. These findings may have important management implications because they suggest that short term changes in the percentage of total stream discharge abstracted may have consequences for the downstream migration success of smolts.

2025, Limnetica

Salmo trutta is a key species of headwater streams that is able to influence the structure of these ecosystems through predation. Populations of this species are being threatened by climate change and hydrological alteration. In order to understand how their disappearance would affect the ecosystem structure of headwater streams, we used cage experiments to analyse different biofilm and macroinvertebrate structural parameters and the biodiversity of their communities under different trout densities. Due to a heavy rain event, our experiment was destroyed on the 10 th day, but the role of trout as stream ecosystemic structure drivers was observed, as multiple parameters were modulated by their presence or absence. In the high-density treatments, a significant reduction in the biomass of macroinvertebrate families that fed on biofilms was observed due to direct predation on them, which caused the biofilms to be more autotrophic. A decrease in brown trout population densities could cause cascading trophic effects on the ecosystem structure of headwater streams.

2025, Limnetica

Salmo trutta is a key species of headwater streams that is able to influence the structure of these ecosystems through predation. Populations of this species are being threatened by climate change and hydrological alteration. In order to understand how their disappearance would affect the ecosystem structure of headwater streams, we used cage experiments to analyse different biofilm and macroinvertebrate structural parameters and the biodiversity of their communities under different trout densities. Due to a heavy rain event, our experiment was destroyed on the 10th day, but the role of trout as stream ecosystemic structure drivers was observed, as multiple parameters were modulated by their presence or absence. In the high-density treatments, a significant reduction in the biomass of macroinvertebrate families that fed on biofilms was observed due to direct predation on them, which caused the biofilms to be more autotrophic. A decrease in brown trout population densities could caus...

2025, River Research and Applications

Many studies focus on stream water temperature (WT) because it is considered a key ecological factor. However, few of them have investigated the use of WT data from water level monitoring networks, which often measure WT as ancillary data. Our study was conducted in southern Belgium at a high temporal resolution with continuous data recorded at intervals of 10 min between 2012 and 2016 and large spatial scale greater than 16,000 km 2 . This study aimed to assess whether a regional water level network (140 stations) is reliable for continuous WT monitoring based on a Bland-Altman analysis with WT collected through a European monitoring network (Water Framework Directive). This study also investigates whether WT data acquired by water level stations can be used to perform both state-of-the-art visualization of thermal regimes and spatio-temporal queries for specific ecological monitoring. We found that the water level stations were reliable tools in recording continuous WT in the streams of the study area. The temperature difference between the two WT monitoring networks was -0.57°C on average. Our positive results promote the use of WT from water level stations in order to globally characterize the thermal regime of streams as well as to provide spatial or temporal information on this regime at high frequencies. As an example, our data showed the effectiveness for brown trout (Salmo trutta fario L.) in spatializing thermal risk areas related to the thermal requirement of this fish species; in 2015, 19% of stations located in brown trout fish zone recorded temperatures above 25°C.

2025

 Context • « Water temperature: the ecological master factor » J.R. Brett (1971)1 • How to effectively monitor water temperature? Water temperature monitoring network (e.g. water framework monitoring) Potential of ancillary data source like gauging network? • How can river managers take into account water temperature (e.g. riparian shade management)? USING GAUGING NETWORK FOR REGIONAL MONITORING OF STREAM WATER TEMPERATURE (WALLONIA, BELGIUM) Utilisation d’un réseau de stations de jaugeage pour le monitoring régional de la température des cours d’eau (Wallonie, Belgique)

2025

From June to August 2002, data storage tags (Star-Oddi DST milli) were used to record the vertical movements of seven ferox. Tags from two fish (3.4kg and 3.7kg) have been recovered to date. The larger 3.7kg fish spent most of June in a depth of around 6m. During the day this ferox often undertook one or more short (<30 minute) dives to 11m while on approximately one third of nights it rose to within 2m of the surface (Figure 2). By August, this fish was, almost without exception, rising to the surface 2m every night. During daylight hours it would move to a depth of between 3 and 5m from where it undertook one or more short dives to a maximum of 9m. The box plot of depth against time of day clearly shows this diel pattern (Figure 3).

2025, Scientific Reports

Ecological speciation – whereby an ancestral founder species diversifies to fill vacant niches – is a phenomenon characteristic of newly formed ecosystems. Despite such ubiquity, ecosystem-level effects of such divergence remain poorly understood. Here, we compared the trophic niche of European whitefish (Coregonus lavaretus) and their predators in a series of contrasting subarctic lakes where this species had either diversified into four ecomorphologically distinct morphs or instead formed monomorphic populations. We found that the trophic niche of whitefish was almost three times larger in the polymorphic than in the monomorphic lakes, due to an increase in intraspecific specialisation. This trophic niche expansion was mirrored in brown trout (Salmo trutta), a major predator of whitefish. This represents amongst the first evidence for ecological speciation directly altering the trophic niche of a predator. We suggest such mechanisms may be a common and important – though presently...

2025, Genes

Brown trout (Salmo trutta), like many other freshwater species, is threated by the release in its natural environment of alien species and the restocking with allochthonous conspecific stocks. Many conservation projects are ongoing and several morphological and genetic tools have been proposed to support activities aimed to restore genetic integrity status of native populations. Nevertheless, due to the complexity of degree of introgression reached up after many generations of crossing, the use of dichotomous key and molecular markers, such as mtDNA, LDH-C1* and microsatellites, are often not sufficient to discriminate native and admixed specimens at individual level. Here we propose a reduced panel of ancestry-informative SNP markers (AIMs) to support on field activities for Mediterranean trout management and conservation purpose. Starting from the genotypes data obtained on specimens sampled in the main two Molise's rivers (Central-Southern Italy), a 47 AIMs panel was identified and validated on simulated and real hybrid population datasets, mainly through a Machine Learning approach based on Random Forest classifier. The AIMs panel proposed may represent an interesting and cost-effective tool for monitoring the level of introgression between native and allochthonous trout population for conservation purpose and this methodology could be also applied in other species.

2025, Fisheries Research

Recreational fishing has grown substantially worldwide; for some recreational fisheries both catch and economic value now exceeds that of commercial fisheries. Monitoring of recreational fisheries effort and catch is therefore important for sustainable fisheries management. We developed and implemented an angler survey to estimate effort and catch for the recreational trolling fishery for landlocked Atlantic salmon (Salmo salar) and brown trout (S. trutta) in Lake Vänern, Sweden. Major challenges were the large spatial scale and dispersed fishing effort, a lack of revenue from fishing licence sales, and a lack of catch reporting requirements. We developed a complemented roving/mail-in survey to estimate effort and catch during the main fishing periods, spring and fall, 2014. Instantaneous counts from major access sites were used for effort estimates, and mail-in surveys were used for catch rates. Our results show that Vänern supports a salmon and trout fishery of some 28.7 ± 3.3 tonnes per year. Fishing effort was higher in the spring than in the fall, and there were seasonal differences in catch rates for trout but not for salmon. Estimates show that the recreational trolling fishery now harvests more salmon and trout annually than do the commercial and subsistence fisheries combined. This highlights the importance of continuing an angler survey program for Vänern as a key element for sustainable fisheries management, and can serve as a model for other recreational fisheries at large spatial scales.

2025, Transactions of the American Fisheries Society

We tested how depth and cobble clusters affected pool use by brown trout Salmo trutta in four enclosures in a seminatural, outdoor stream channel. Into each enclosure, which consisted of a shallow, cobblefilled habitat and a deeper pool, we stocked eight brown trout 9-19 cm long that had been tagged with passive integrated transponders (PIT). Receiver antennae for the PIT tags were placed between the two habitats to allow continuous monitoring of movements of individual fish. We found that trout used pools to a greater extent at night than during the day. Alterations of depth and substrate had no effect on pool use at night. During the day, increasing water depth either alone or together with adding cobbles increased pool use, whereas cobble addition alone had no effect on pool use. We suggest that evaluations of physical habitat modifications in streams should include measurements of population responses as well as information on how, when, and which fish use newly created habitat structures.

2025, The Bulletin of the Ecological Society of America

April 2021 3 Photo Gallery These photographs illustrate the article "Thermal conditions during embryogenesis influence metabolic rates of juvenile brown trout Salmo trutta.

2025, Journal of Aquatic Animal Health

A polyphasic characterization of atypical isolates of Yersinia ruckeri (causative agent of enteric redmouth disease in trout) obtained from hatchery‐reared brown trout Salmo trutta in South Carolina was performed. The Y. ruckeri isolates were biochemically and genetically distinct from reference cultures, including the type strain, but were unequivocally ascribed to the species Y. ruckeri, based on API 20E, VITEK, fatty acid methyl ester profiles, and 16S rRNA gene sequencing analysis. These isolates were nonmotile and unable to hydrolyze Tween 20/80 and were therefore classified as Y. ruckeri biotype 2. Genetic fingerprint typing of the isolates via enterobacterial repetitive intergenic consensus (amplified by polymerase chain reaction) and fragment length polymorphism showed biotype 2 as a homogeneous group distinguishable from other Y. ruckeri isolates. This is the first report of Y. ruckeri biotype 2 in the USA.

2025, Fishes

eDNA appears well positioned to play a significant role in the future of biomonitoring, and the need to assess the efficacy of eDNA-based surveys in a variety of habitats is increasing. We conducted an eDNA metabarcoding-based survey of fish communities in the Great Smoky Mountains National Park (GSMNP), located in eastern Tennessee and western North Carolina. The GSMNP, widely recognized as a biodiversity hotspot, encompasses 211,419 hectares of the Southern Appalachian Mountains with elevations up to 2205 meters and is home to approximately 73 species of fish, including 12 families and three species classified as endangered or threatened. We collected 50 water samples in first to sixth order streams at elevations of 336 to 1462 meters, including all major watersheds found in the park. eDNA was amplified utilizing two primer sets which each target differing regions of the 12S mitochondrial gene and generate amplicons of varying size (97 and 225 bp, respectively), and sequencing was conducted to an expected read depth of 400,000 reads per sample per marker. We detected a total of 40 fish species; of these, 36 were detected with the primer set which produces a 97 bp amplicon, and 12 of these 36 were detected only by this primer set. Species assemblages varied between stream orders, and species richness decreased with increasing elevation and increased with increasing stream order. Significant correlations were observed between biomass data from electrofishing monitoring (1984-2023) and eDNA metabarcoding read counts in five of seven species examined, including all salmonids. eDNA metabarcoding was demonstrated to be effective in assessing fish communities in high-elevation lotic systems in the Southern Appalachians, and our results suggest that primers targeting shorter amplicons may exhibit greater efficacy in these ecosystems.

2025, SIBIC 2022

Management Measures for the Conservation of Freshwater Pearl Mussel (Margaritifera margaritifera) and Brown Trout (Salmo trutta) in

2025, The IX Iberian Congress of Ichthyology

Brown trout (Salmo trutta) has high ecological and socio-economic importance in many cold-water rivers of northern and central Portugal. However, no studies have addressed the ecology of this species on a large scale. To understand factors driving Brown trout populations in diverse Portuguese streams, we sampled 33 sites, during the summer season of 2020, in cold-water rivers of Minho, Lima, Neiva, Cávado, Ave, Douro, and Vouga basins. Brown trout populations were characterised by several populations and growth parameters, including abundance, density, biomass, age, and body condition. The relationships of these parameters with environmental variables, biotic factors, and fishery management regulations were analysed, and the reference parameters of the populations were defined. There was a good/excellent ecological integrity in most sites, assessed by several water-quality-related, hydromorphological, and biological metrics. Nevertheless, several threats were identified-namely, the riparian degradation (e.g., mortality of alder trees), the presence of exotic species, habitat fragmentation, overfishing, stocking, and more recently, extended dry periods. Portuguese populations showed higher growth rates but lower density, biomass, and physical condition. Intra-and interspecific competition did not seem to play relevant roles in the regulation of brown trout populations, and the common fishery management appears to have no clear positive impact on the natural sustainability of these wild populations. In this context, under the POSEUR 03-2215-FC-000096 project, several studies were developed for in situ conservation and ex situ reproduction of wild brown trout populations. Global genetic characterisation of brown trout populations was made, and eight wild stocks were selected and acclimated to the captivity for implementation of stocking programs. Furthermore, the rehabilitation of riparian corridors and the implementation of specific exploitation and management plans were also developed for the conservation of sympatric populations of brown trout and the critically endangered freshwater pearl mussel Margaritifera margaritifera in Portuguese mountain rivers.

2025

This work is the result of sport fishing monitoring carried out in 2013 in the Reserved Fisheries Zone (ZPR) of the Olo River. The aim of this initiative was to evaluate whether the management model, initially established, would require, after six years of implementation, eventual modifications, and to stabilize, in a Management Plan, the recreational sport fishing activity during the next years of activity. This study respected the methodology originally adopted (2007). In the conservation status assessment of the fish communities, the data concerning age, growth, physical condition and their relationship with the different habitat types where they were captured were analyzed. The results showed that the brown trout and the northern chub are once more the species with the most spatial distribution (found along the entire river). Also, revealed that the salmonid was present in all the sampling stations with water available throughout the year. The recent occurrence of a trout specim...

2025, Biology & Environment: Proceedings of the Royal Irish Academy

Plantation forests were established on western Irish peatlands before it became apparent that riparian buffer zones were essential for the health of important salmonid habitats and aquatic ecosystems. The option to retrofit a riparian buffer zone several years prior to the clearfelling of the main plantation may lessen the possible effect of the clearfelling on receiving waters and provide some protection against sediment and nutrient runoff. The option to create a RBZ can only be considered if it can be shown that clearfelling this zone of coniferous forestry along the stream does not pose a significant risk to the water bodies in the short term. To assess this risk, the hydrology, water chemistry and biota at three locations in western peatland catchments within mature, harvestable-age forestry plantations were studied prior to, during and immediately after riparian buffer zones were created. Results indicate that water discharge and suspended sediment increased significantly at two experimental sites post-felling. Maximum and minimum daily temperature and pH also increased significantly at two of the sites. The biological results from macroinvertebrate analysis indicated some significant changes in richness and abundance of species post-felling. The juvenile trout (Salmo trutta L.) densities remained stable over the sampling period and appeared unaffected by the clearfelling operations.

2025

Ich versichere, dass ich diese Doktorarbeit selbständig und nur unter Verwendung der angegebenen Hilfsmittel angefertigt habe. Weiterhin versichere ich, die aus benutzten Quellen wörtlich oder inhaltlich entnommenen Stellen als solche kenntlich gemacht zu haben. Aachen, am 18 März 2015 Special thanks go to Udo Hommen, my PhD supervisor, for recruiting me into the CREAM-EU project whereby I was given the chance to persue my PhD studies. Udo's friendliness, prompt and constructive academic guidance, understanding, flexibility and unconditional support for academic and non-academic issues made my journey lighter and most importantly pleasant and, when unnecessary, stress-free. In this research project, I had Udo's support and ever valuable scientific input whenever I asked for it, but what was best was that I had the freedom to shape this project to reflect my spirit and personality, so thank you Udo for that. Many thanks and appreciation goes to Thomas G. Preuss for being a great modelling workgroup leader, for making me feel genuinely welcome and supported, and definitely for the valuable scientific input and guidance throughout. Thanks to my PhD advisors, Toni Ratte and Andreas Schäffer, for assistance when needed, and to Martina Roß-Nickoll for welcoming me into her workgroup around the end of my PhD period. Thanks to Pernille Thorbeck, Paul Van den Brink, Andreas Focks and Charles RE Hazlerigg for the willingness to cooperate and for fruitful discussions during the early formulation of the Minnow IBM. Special thanks go to Charles for making available his NetLogo program for the zebrafish IBM and his dissertation. Thanks to Volker Grimm for being a very supportive CREAM project leader, also for reviewing and contributing to the formulation of the Minnow IBM and the TRACE document. Thanks to the CREAM organisers, and the Fraunhofer-IME and the BioV secretaries who took care of all the paperwork promptly and perfectly and saved me a lot of time and trouble. Thanks to my collegues, especially the members of my work group, for the good times we had, and to my very dear friends Devdutt Kulkarni and Faten Gabsi whose company I have enjoyed all along. Thanks to Andre Gergs for helping me settle in Aachen during my Chapter 2: A list of fish species that are potentially exposed to pesticides in edge-of-field water bodies in the European Union-a first step towards identifying vulnerable representatives for risk assessment Published in a slightly modified form as Ibrahim L, Preuss TG, Ratte HT, Hommen U (2013) A list of fish species that are potentially exposed to pesticides in edge-of-field water bodies in the European Union-a first step towards identifying vulnerable representatives for risk assessment.

2025, Journal of Applied Ichthyology

The high cost and unpredictable availability of fish meal and fish oil (FO) forced feed mill companies to look for alternative ingredients for aquafeeds. In this study, the effects of alternative dietary lipid sources [FO as control, canola oil (CO), oleine oil (OO), poultry fat (PF) and pork lard (PL)] in trout feed on flavour volatile compounds occurring in brown trout (Salmo trutta L.) fillet were evaluated after 70 days of feeding (rearing temperature 14.6°C). Total amounts of volatile compounds identified were higher for fillets of fish fed diets containing only FO as lipid sources. Total amount of alcohols and aldehydes of the fillets were linearly directly related to the percentage content of polyunsaturated fatty acids (PUFA) n-3 of brown trout flesh. The use of alternative dietary lipid sources, modifying the fillet fatty acids composition, affect the total amount of volatile compounds and, changing the relative amount of each volatile compound, affect the flavour of the fish flesh.

2025

Breeding has moved beyond the point of simply propagating random stock. Genetic potential can be improved by establishing and crossing genetically defined strains, crossing species and manipulating gametes. Some of these activities require cryopreservation of semen. Cryopreserved sperm could also be a means of exchange of genetic material between locations and populations when transportation of live fish is restricted. In this study we had a survey on rainbow trout sperm quality in Genetic and Breeding Center for Coldwatwr Fishes, Shahid Motahari, Yasouj. Then Cryopreservation trials on rainbow trout (Oncorhynchus mykiss) sperm were carried out using six basic extenders. Egg batches of 25 g were inseminated with semen frozen in five 0.5-ml straws. Thowing temperature of cryopreserved sperm also was tested. In anather trial we investigate different cryoprotectant. The result showd that the best period for sperm collection in this center was from Novamber to January. The best extender...

2025, Transactions of The American Fisheries Society

Entrainment in irrigation canals has been considered a major source of mortality for some fish populations. However, the magnitude of fish loss from entrainment is usually not evaluated from a basinwide perspective, thus precluding an assessment of populationlevel consequences. We incorporated such a perspective in evaluating entrainment losses of Bonneville cutthroat trout Oncorhynchus clarkii utah and brown trout Salmo trutta in a southwestern Wyoming river basin that is used for irrigating agricultural crops. We estimated the number of Bonneville cutthroat trout and brown trout (.150 mm TL) entrained in irrigation canals and then compared these numbers to population estimates within the river main stem and across the entire basin. We also examined previous studies to determine annual mortality rates for assessment of realized losses to irrigation canals. Small percentages of the Bonneville cutthroat trout (1.2-3.3%) and brown trout (0.4-1.2%) populations within the basin were entrained in 2004 and 2005. These values were much lower than the total annual mortality rates for inland riverine cutthroat trout O. clarkii (57.4%) and brown trout (56.4%) in the mountain west region of the United States. Examining the number of entrained fish in context with the basinwide population and total annual mortality allows evaluation of the significance of fish entrainment losses to irrigation canals.

2025, Transactions of The American Fisheries Society

The effects of multiple nonnative piscivore species on native prey species in lentic systems are poorly understood. We studied the relative predation risks posed by two piscivorous salmonids (brown trout Salmo trutta and lake trout Salvelinus namaycush) to endemic roundtail chub Gila robusta in two lakes within the upper Colorado River basin. Gill nets were set in various habitat types to study habitat use by the three species before and after the onset of summer stratification. Roundtail chub and brown trout were mainly associated with shallow-water habitats, and this association did not change with thermal period. By contrast, lake trout habitat use changed with thermal period as fish moved from shallow areas in the spring to deepwater habitat after stratification. These habitat use patterns indicate that roundtail chub are more susceptible to predation by brown trout than by lake trout because both roundtail chub and brown trout occupy the littoral zone for a prolonged period. Diet data indicated that brown trout consumed littoral fish species (i.e., cyprinids), whereas lake trout primarily consumed opossum shrimp Mysis spp. and dipterans (true flies). Brown trout consumed proportionally more fish than did lake trout, began feeding on fish at smaller total lengths, and increased fish consumption during the period of thermal stratification. An important consideration for efforts to conserve lentic roundtail chub populations is the prevention of future introductions of littoral predators.

2025, High Mountain Conservation in a Changing World

High mountain lakes are originally fishless, although many have had introductions of non-native fish species, predominantly trout, and recently also minnows introduced by fishermen that use them as live bait. The extent of these introductions is general and substantial often involving many lakes over mountain ranges. Predation on native fauna by introduced fish involves profound ecological changes since fish occupy a higher trophic level that was previously inexistent. Fish predation produces a drastic reduction or elimination of autochthonous animal groups, such as amphibians and large macroinvertebrates in the littoral, and crustaceans in the plankton. These strong effects raise concerns for the conservation of high mountain lakes. In terms of individual species, those adapted to live in larger lakes have suffered a higher decrease in the size of their metapopulation. This ecological problem is discussed from a European perspective providing examples from two study areas: the Pyrenees and the Western Italian Alps. Species-specific studies are urgently needed to evaluate the conservation status of the more impacted species, together with conservation measures at continental and regional scales, through regulation, and at local scale, through restoration actions, aimed to stop further invasive species expansions and to restore the present situation. At different high mountain areas of the world, there have been restoration projects aiming to return lakes to their native fish-free status. In these areas autochthonous species that disappeared with the introduction of fish are progressively recovering their initial distribution when nearby fish-free lakes and ponds are available.

2025, Annales Zoologici Fennici

In order to create a new equilibrium fish community, in which fish consumption by piscivorous fish equals the production of prey fish, mass removal of unwanted fish and intensified stocking of young-of-the-year pikeperch has been performed in Lake Köyliönjärvi. A revised bioenergetics model of walleye (Stizostedion vitreum vitreum) was used for pikeperch to calculate consumption rates from the growth rate, fish population size and ambient temperature. According to model calculations, food consumption of pikeperch alone is insufficient to control production of prey fish in Lake Köyliönjärvi. Combinations of fishing restrictions, removal of unwanted fish and intensified stocking are needed to enhance the pikeperch population and its predatory effect. siderable internal nutrient loading through their feeding activities. In order to improve water quality and to balance the fish community, biomanipulation of Lake Köyliönjärvi has been performed since 1992. Manipulation has included mass removal of unwanted fish, mainly cyprinids and smelt (Osmerus eperlanus), and, lately, intensified stocking of piscivorous fishes such as pikeperch and pike (Esox lucius). These measures aim to permanently change the fish community structure. The ultimate target is a new equilibrium fish community in which fish consumption by piscivorous fish equals the production of unwanted prey fish.

2025, Tarım Bilimleri Dergisi

Three diets were tested to feed triplicate groups of Salmo trutta abanticus fry with initial average body weight of 0.091 g in fiberglass tank. Two diets consisted of live guppy fry (Lebistes sp.), tubifex (Tubifex tubifex) and third diet was compound diet made up from commercial trout feed. At the end of 12 week of feeding, the best results for average daily growth, specific growth rate, feed conversion ratio, protein efficiency ratio, daily growth index, feed efficiency, plasma total protein, weight increase, mean weight gain and survival rate were observed for the group fed with guppy fry (P<0.05) whereas the poorest results were obtained for the group fed with compound diet.

2025

The Salmonidae fish family is well represented in Romanian fauna, with a total of six species in the wild and reared in fish farms. Among them, the brown trout ( Salmo trutta fario ) can be found in all major Romanian river basins. However, anthropogenic activities might disrupt salmonids’ habitats, so that inbreeding and genetic isolation might easily occur in the wild populations. We analyzed two wild brown trout populations from rivers targeted by anthropogenic activities, by using nuclear markers and genotyping in order to observe their genetic structure. We analyzed nine microsatellites and we observed their alleles frequencies, number of private alleles, observed and expected heterozygosity, as well as their population structure. The two populations are not in Hardy-Weinberg equilibrium for most of the loci and the inbreeding coefficient for both populations suggests a heterozygote deficit. Further sequencing data are needed in order to have a better view upon their complete g...

2025, Aquatic Living Resources

The Carpathian Mountains are one of the most complex orogenetic areas of Europe, with unique fauna, including the brown trout (Salmo trutta). In this study we performed population genetic analysis of 12 differentS. truttapopulations using two types of molecular markers: nine microsatellites and mitochondrial D-loop sequences. The following working hypothesis was considered: the Romanian Carpathians and their surrounding lowlands can be key relief units based on which theS. truttagenetic diversity, spread, distribution, connectivity, relative isolation and genetic divergence can be at least partially explained. The phylogenetic analysis revealed that the majority of sequences were grouped in the Danubian clade. The high haplotype diversity of the 12 analyzed brown trout populations can be explained by the high nucleotide diversity. The microsatellite analysis revealed an inbreeding event for all the loci and for the populations analyzed. The Romanian Carpathians' shape and geogra...

2025, Transylvanian Review of Systematical and Ecological Research

Among the species of salmonids that exist in Romania, the most common is the brown trout (Salmo trutta, morpha fario, Linnaeus, 1758), with a high commercial potential, being used for aquaculture or fishing. Unfortunately, its natural habitat is disrupted by human activities and in order to avoid local extinction of Salmo trutta fario repopulation strategies are being applied. The repopulation activities must be carefully designed and conducted taking into consideration that there is a high risk of hybridization. Our study aims to analyze the genetic diversity of three Romanian brown trout populations found in rivers in the Făgăraş Mountains using mitochondrial markers. Standard DNA extraction protocol with phenol-chloroform was applied to the biological material represented by small fin fragments sampled from 80 individuals of brown trout, followed by PCR amplification of D-loop control region and Sanger sequencing. Alignment and editing of all the sequences obtained were carried o...

2025, Journal of Fish Biology

The last of 12 brown trout Salmo trutta stocked in a small pond in south-east Norway in 1979 were caught in July 2011. These fish represent a curiosity regarding longevity and growth pattern, and ageing from otoliths was consistent with the known life history of this specimen. Despite almost total stagnation in growth since the age of 16 years, the testes were fully developed.

2025, 18

NINA Rapport Dette er en ny, elektronisk serie fra 2005 som erstatter de tidligere seriene NINA Fagrapport, NINA Oppdragsmelding og NINA Project Report. Normalt er dette NINAs rapportering til oppdragsgiver etter gjennomført forsknings-, overvåkings-eller utredningsarbeid. I tillegg vil serien favne mye av instituttets øvrige rapportering, for eksempel fra seminarer og konferanser, resultater av eget forsknings-og utredningsarbeid og litteraturstudier. NINA Rapport kan også utgis på annet språk når det er hensiktsmessig. Som navnet angir behandler temaheftene spesielle emner. Heftene utarbeides etter behov og serien favner svaert vidt; fra systematiske bestemmelsesnøkler til informasjon om viktige problemstillinger i samfunnet. NINA Temahefte gis vanligvis en populaervitenskapelig form med mer vekt på illustrasjoner enn NINA Rapport. Faktaarkene har som mål å gjøre NINAs forskningsresultater raskt og enkelt tilgjengelig for et større publikum. De sendes til presse, ideelle organisasjoner, naturforvaltningen på ulike nivå, politikere og andre spesielt interesserte. Faktaarkene gir en kort framstilling av noen av våre viktigste forskningstema. Annen publisering I tillegg til rapporteringen i NINAs egne serier publiserer instituttets ansatte en stor del av sine vitenskapelige resultater i internasjonale journaler, populaerfaglige bøker og tidsskrifter.

2025, 34 s.

2025, Springer eBooks

The autumn and spring descent of 41 brown trout kelts (spent trout) (average total length L t 75.9 cm) and the spring descent of 27 hatchery-reared smolts (average L t 26.2 cm) were studied by radiotelemetry in 1993/1994 (kelts) and 1997/1998 (kelts and smolts) at the Hunderfossen dam and power plant, south-east Norway. In 1999 we studied spring descent of 48 untagged kelts by visual observations and video-monitoring at one spillway. In autumn 1993 and 1997, 62.4% and 44.0% of the tagged kelts migrated downstream to the dam at water temperatures between 0.1 and 0.8°C. During release of spillwater, the kelts gathered along the dam with limited movements. Neither smolts nor kelts used the 2 m submerged turbine shafts as a pathway to migrate downstream Hunderfossen dam. Nor did release of large amounts of deep water through spillways provide downstream migration possibilities for kelts and possibly for smolts. The majority of both smolts and kelts migrated downstream at short periods of surface water release through the spillways, indicating high importance of surface water release. The threshold value of descend of kelts at surface release was between 1 and 4 m 3 s -1 which correspond to a water column between 12 and 36 cm. These findings are highly relevant regarding hydroelectric development in river systems containing iteroparous salmonid species.

2025, Regulated rivers

The migration pattern of spawners of brown trout (Salmo trutta) in relation to water flow was analysed by radio-tracking in the regulated River Gudbrandsdalsligen, Norway. During the upstream spawning migration in the high flow period, trout (2-12 kg) were caught, tagged and released 15 km downstream of a fish ladder at the Hunderfossen waterfall. The released fish displayed a systematic and directional upstream movement to the outlet of the tunnel from the hydroelectricity plant. In autumn and winter there is a minimum water discharge of 20-2m3/s on p.s. in the river between the dam and the outlet of the tunnel, which has a discharge of 200-300m3/s. When the water flowing over the Hunderfossen dam decreased to 20m3/s, the ascent of brown trout up the river stopped and fish periodically entered the power plant tunnel. To determine the flow necessary to attract fish into the spawning reach above the tunnel outlet, two experiments were undertaken using 12 and 17 radio-tagged trout. In the first experiment, 60m3/s of water released for 24 h resulted in the migration of 50% of the trout up the river. The second experiment, releasing 60 m3/s for 24 h, followed by 30m3/s for 24h two days later, resulted in the migration of 60% of the trout. Only one fish ascended the river at a flow of 30 m3/s. It is recommended that a repeated release of water at 60 m3/s is made in periods of minimum water discharge to save the spawning migration. The results demonstrate the advantage of using radio-tracking in experiments dealing with fish migration in relation to water-flow management.

2025, 26 s.

2025

Dam constructions prevent fish migrations. Fishways are a common method to mitigate negative effects. In Norway there are 420 fishways, of which 85% is constructed for anadromous salmonids. Research and the design of fishways have largely focused on upstream migration and migratory species like Atlantic salmon and sea trout which have strong swimming capacity. As for salmon, inland fish species, need efforts to secure both up-and downstream migration. Two-ways communication between spawning and other vital habitats are imperative to conserve their natural life history including multiple spawning (iteoparity). Connectivity is an important concept in relation to the ongoing revisions of hydropower stations, and to meet the requirements of the EU Water Framework. Good ecological status of rivers presupposes minor deviations from the natural condition of the composition, abundance, and age structure of fish species, i.e. as if the water body was not affected by interference or pollution. This literature study highlights the need to apply a holistic approach to fish passage facilities.

2025, Regulated Rivers: Research & Management

2025, Journal of Fish Biology

The last of 12 brown trout Salmo trutta stocked in a small pond in south‐east Norway in 1979 were caught in July 2011. These fish represent a curiosity regarding longevity and growth pattern, and ageing from otoliths was consistent with the known life history of this specimen. Despite almost total stagnation in growth since the age of 16 years, the testes were fully developed.

2025

Kraabøl, M. & Nashoug, O. 2010. Fiskevandringer forbi kraftverk og dammer i Rena og Glomma: Systemforståelse, lokal og internasjonal basiskunnskap og innspill til instrukser ved de enkelte fiskepassasjene - NINA Rapport 537. 47 s. Denne rapporten er utarbeidet med bakgrunn i tidligere utredning av fisketrappene i Glommavassdraget og nye befaringer ved de enkelte fisketrappene. De nye befaringene ble gjennomført 13. og 17. november 2008, samt 28. april 2009. Befaringene omfattet fisketrapper og flomluker ved Høyegga dam, Strandfossen kraftverk, Skjefstadfoss kraftverk, Braskereidfoss kraftverk, Kongsvinger kraftverk og Funnefoss kraftverk i Glomma, Storsjødammen og Løpet kraftverk i Søndre Rena og Valmen kraftverk i Søre Osa. Under befaringene ble fisketrappene og tilhørende konstruksjoner og elvestrekninger også vurdert med henblikk på tiltak for fiskevandringer. Samtlige kraftverksdammer i Glomma og Rena har en eller flere fisketrapper. Kunnskapsgrunnlaget fra alle disse trappene e...

2025

The EU Water Framework Directive and the monitoring of fish populations in large rivers and lakes: The EU Water Framework Directive is implemented as The Water Regulations in Norway to ensure a more holistic and ecosystembased water management, and if necessary, initiate preventive or improving environmental measures to ensure environmental conditions in freshwater, groundwater and coastal waters. Accordingly, regional programs that provide a holistic monitoring of the status of water bodies should be developed. These programs should include relevant ecological, chemical, quantitative and physical parameters. There is however significant methodological problems in terms of getting a good and accurate monitoring for several of the themes involved. We have focused on the monitoring of fish populations in large rivers and lakes. Based on the description in The Water Regulations, the composition, size and age structure of fish populations form the basis for classification of ecological status. This represents a methodological challenge since traditional methods like ordinary electrofishing and gillnets are not applicable, especially not in large rivers. We have acquired two electrofishing boats to examine fish populations in large rivers and our experience after 5 years is that this method covers the requirements of The Water Regulations in relation to monitoring and assessing ecological condition. This we demonstrate through several examples where we have used electrofishing boats for monitoring fish populations in rivers and littoral zones of lakes.

2025

Dette er en elektronisk serie fra 2005 som erstatter de tidligere seriene NINA Fagrapport, NINA Oppdragsmelding og NINA Project Report. Normalt er dette NINAs rapportering til oppdragsgiver etter gjennomført forsknings-, overvåkings-eller utredningsarbeid. I tillegg vil serien favne mye av instituttets øvrige rapportering, for eksempel fra seminarer og konferanser, resultater av eget forsknings-og utredningsarbeid og litteraturstudier. NINA Rapport kan også utgis på annet språk når det er hensiktsmessig. Som navnet angir behandler temaheftene spesielle emner. Heftene utarbeides etter behov og serien favner svaert vidt; fra systematiske bestemmelsesnøkler til informasjon om viktige problemstillinger i samfunnet. NINA Temahefte gis vanligvis en populaervitenskapelig form med mer vekt på illustrasjoner enn NINA Rapport. Faktaarkene har som mål å gjøre NINAs forskningsresultater raskt og enkelt tilgjengelig for et større publikum. De sendes til presse, ideelle organisasjoner, naturforvaltningen på ulike nivå, politikere og andre spesielt interesserte. Faktaarkene gir en kort framstilling av noen av våre viktigste forskningstema. Annen publisering I tillegg til rapporteringen i NINAs egne serier publiserer instituttets ansatte en stor del av sine vitenskapelige resultater i internasjonale journaler, populaerfaglige bøker og tidsskrifter.

2025