Atlantic salmon Salmo salar, brown trout Salmo trutta (including the anadromous form, sea trout) and Arctic charr Salvelinus alpinus (including anadromous fish) provide important commercial and ...sports fisheries in Western Europe. As water temperature increases as a result of climate change, quantitative information on the thermal requirements of these three species is essential so that potential problems can be anticipated by those responsible for the conservation and sustainable management of the fisheries and the maintenance of biodiversity in freshwater ecosystems. Part I compares the temperature limits for survival, feeding and growth. Salmo salar has the highest temperature tolerance, followed by S. trutta and finally S. alpinus. For all three species, the temperature tolerance for alevins is slightly lower than that for parr and smolts, and the eggs have the lowest tolerance; this being the most vulnerable life stage to any temperature increase, especially for eggs of S. alpinus in shallow water. There was little evidence to support local thermal adaptation, except in very cold rivers (mean annual temperature <6·5° C). Part II illustrates the importance of developing predictive models, using data from a long‐term study (1967–2000) of a juvenile anadromous S. trutta population. Individual‐based models predicted the emergence period for the fry. Mean values over 34 years revealed a large variation in the timing of emergence with c. 2 months between extreme values. The emergence time correlated significantly with the North Atlantic Oscillation Index, indicating that interannual variations in emergence were linked to more general changes in climate. Mean stream temperatures increased significantly in winter and spring at a rate of 0·37° C per decade, but not in summer and autumn, and led to an increase in the mean mass of pre‐smolts. A growth model for S. trutta was validated by growth data from the long‐term study and predicted growth under possible future conditions. Small increases (<2·5° C) in winter and spring would be beneficial for growth with 1 year‐old smolts being more common. Water temperatures would have to increase by c. 4° C in winter and spring, and 3° C in summer and autumn before they had a marked negative effect on trout growth.
Genomic studies have largely been accelerated by the advances of next generation sequencing technologies since the beginning of the millennium. This, in turn, has motivated the generation of more ...reference genome assemblies not only in model organisms but also in species of scientific interest. In the present study, we employed a comparison study between the two different reference genome assemblies available for the same species, Salmo trutta, in GenBank. The results indicated an overall 90% similarity index between the two assemblies. Furthermore, the inversion regions of which assembly needs corrections were detected. Taking into account the whole genome duplication origin of the Salmonidae family, both assemblies were of good quality. However, the updated version of the Wellcome Sanger Institute assembly (fSalTru_1.2) outperformed the Norwegian assembly and was detected as the best available reference genome assembly in Salmo trutta.
Hepcidin, a hepatic antimicrobial peptide, is a key player of the nonspecific immune system. The structure of hepcidin gene from brown trout (Bthepc) has been characterized at the molecular level. ...The 1158-bp mRNA generates a coding sequence (CDS) of 267 bp, which encodes an 88-amino acid protein. Molecular evolution analysis classified Bthepc to the family Salmonidae. Amino acid sequence homologies between Bthepc and hepcidin in other species such as Oncorhynchus mykiss, Salmo salar, and Hucho taimen were found to be 93.18%, 96.59%, and 92.05% respectively. The mature peptide and the signal peptide of Bthepc are made of 25 and 24 amino acids, respectively. Similar to the other species, eight conserved cysteines in the mature peptide of Bthepc are held together by four disulphide bonds. Expression profiling of Bthepc indicated its highest expression in the liver. Further, iron levels or inflammation did not induce the age-dependent expression of Bthepc. Bthepc mRNA expression analysis in six immune tissues (liver, gill, spleen, skin, head kidney and intestine) indicated different levels of increase when challenged with Aeromonas salmonicida and Aeromonas hydrophila. The antimicrobial activity of synthetic Bthepc to typical pathogens was verified in vitro. In addition, Bthepc showed moderate haemolytic activity to mammalian erythrocytes. The antimicrobial activity of Bthepc was attributed to the disruption of the bacterial outer membrane integrity, which was evident from our scanning electron microscopy results. In summary, hepcidin gene of brown trout was characterized, and its antimicrobial activity was verified on different levels.
•Hepcidin cDNA sequence was cloned from a valuable cold-water fish Salmo trutta.•Spatiotemporal expression profiles of hepcidin in Salmo trutta were examined.•Synthetic hepcidin peptide of Salmo trutta exhibited antimicrobial activity in vitro.
The European brown trout, Salmo trutta, is a cold-adapted fish reported as a Least Concern species in the IUCN Red List. This species colonized new territories from southern refuges during the last ...glacial melting, but during the 20th century suffered from anthropic impacts on its habitats. The long-time survival of the species relies on the genetic diversity within and among populations. Brown trout is among the genetically most diverse vertebrate species; however, native populations in Mediterranean rivers have dramatically suffered of introgressive hybridization from extensive releases of evolutionary distant non-native Atlantic stocks. In addition, in Mediterranean rivers climate change will result in unsuitable conditions for the species during the 21st century. Using brown trout populations at the headstreams of a Pyrenean river as a model, this paper revised how hatchery releases have affected the native gene pools and how environmental and climatic variables controlled the amount of local introgression at intra-basin level. Introgressive hybridization was detected in all studied sites. Ten times larger divergence was observed among populations at tributaries than among populations along the main stem. A highly impacted population distributed in a long transect in the main stem suggested that hatchery fish move towards the main stem wherever released. From already highly impacted populations and despite the cessation of hatchery releases, warmer temperatures and lower precipitation expected from climate change will extend the introgressive hybridization along the basin, contributing to the extinction of the native gene pools. Based on available morphological distinction of native, hatchery and hybrid brown trout, we advocate the involvement of regional social groups (e.g. riverside dwellers, anglers, conservationists, hikers) in citizen science programs to detect the spread of non-native phenotypes along the rivers. These are cheap and fast methods to collaborate with fishery managers in the preservation and recovery of the regional native populations.
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•Mediterranean trout populations often reinforced with Atlantic hatchery stocks•Variable amounts of Introgressive hybridization of Atlantic genes among populations•Amount of introgression relies on low habitat quality rather than on local stocking•Warmer temperatures and lower precipitation also favored hybridization•Ongoing climatic change will promote the spread of these hybridized populations
Mediterranean brown trout (Salmo trutta) populations have been extensively supplemented with genetically divergent hatchery stocks to enhance recreational fishing, and the displacements of native ...gene pools are well documented. Because of the great difficulty to breed local stocks of native Mediterranean brown trout in the farm, the introduction of Atlantic sterile individuals such as triploids has been proposed as an alternative to the traditional exogenous stocks. Several protocols of optimization and production of triploid fish have been described in S. trutta, nonetheless triploidy is not always induced in the totality of individuals. Therefore, a cost-effective and rapid method is necessary for triploidy verification. Several methods have been used to confirm triploidy, many of them costly in time and effort, and some providing approximate results. Here, we validated highly polymorphic DNA markers –microsatellites– as a rapid, useful and easy tool to detect triploidy. A total of 16 putative triploids, induced by a shock-heat treatment that suppressed the formation of the second polar body, were genotyped with nine microsatellites. All but two individuals showed a pattern of three peaks that corresponded to three alleles at least at one locus, and thus were confirmed as triploids. Genotypes of the two remaining individuals fit on a diploid genome. Our results provide useful insights into the development of alternative methods to assess triploidy in brown trout. Because a large number of microsatellites have been described for many species the use of these highly polymorphic markers to detect triploidy is a valuable tool to be applied in hatcheries.
•Triploidy induction is used to get sterile hatchery fish to reinforce brown trout populations•Triploidy induction is not 100% effective and methods to verify triploidy are necessary•Highly polymorphic microsatellite markers can be used as an easy and cost-effective method to verify triploidy
The cDNA of rbp1a, rbp2a, rbp2b, rbp5, and rbp7b genes was cloned and characterized in brown trout, and their mRNA expressions in response to different levels of dietary soybean oil (SBO) were ...determined along with their growth parameters, muscle fatty acid (FA) profile, and hepatic retinol level. Dietary SBO did not affect the growth parameters, survival, and hepatosomatic index. The FA composition and retinol content of fish reflected those of experimental diets. The retinol-binding proteins (Rbps; except Rbp5) contained lipocalin domains. The phylogenetic analysis showed that brown trout rbps are orthologs of the rbp/RBPs from other vertebrates; this was also supported by identity/similarity analysis. The rbp genes were exhibited to have conserved synteny with zebrafish and human rbps/RBPs. The tissue-specific transcription of duplicated rbp2a and rbp2b genes varied among all the tested tissues. Moreover, the diet including 100% SBO affected the rbp2a and rbp2b mRNA transcriptions differently, and this was explained by the divergence of the transcriptional regulation site of these genes due to the teleost-specific whole genome duplication. rbp1b and rbp7a were lost in the brown trout genome most likely because of nonfunctionalization. The mRNA expression of all the rbp genes studied was affected by dietary SBO. Therefore, their mRNA expressions could be modulated by dietary FAs and retinol content.
•The n-3 HUFA biosynthesize was sufficient in brown trout fed SBO-based diets for optimal growth and survival.•SBO-based diets were not resulted in Vitamin A deficiency.•Duplicated rbp2a and rbp2b genes arose possibly due to neofunctionalization.•mRNA expression of the rbp genes could be modulated by dietary FA and retinol content.
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•Half-extinct species flock of brown trout (5 forms) was studied using aDNA and WGS.•mtDNA and nuclear data confirm the monophyly and recent origin of Sevan trouts.•Stepwise evolution ...from riverine to lacustrine mode of life was revealed.•Climatic oscillations were the likely trigger for speciation of lacustrine forms.•A few SNPs under selection may be responsible for assortative mating.
Five ecologically and phenotypically divergent ecomorphs of the genus Salmo are known from a landlocked alpine lake in the Caucasus, Lake Sevan. It is an example of sympatric diversification within a species-rich lineage with predominate mode of speciation being allopatric. The diversification of Sevan trouts was accompanied by spawning resource partitioning. Four lacustrine ecomorphs with different temporal-spatial spawning strategies and divergent morphology and coloration evolved along with a fifth ecomorph, brook trout, inhabiting the tributaries. Unfortunately, the Sevan trout diversity was almost destroyed by human activity, with two ecomorphs becoming extinct in the 1980s. We performed reconstruction of the evolutionary history of Sevan trouts based on high-throughput sequencing of both contemporary and historical DNA (∼ 50 y.o.) of all Sevan trout ecomorphs. Our study of complete mitogenomes along with genome-wide SNP data revealed the monophyly of four lacustrine ecomorphs and local brook trout, all derived from the anadromous form Caspian salmon, S. caspius. The species tree suggests a scenario of stepwise evolution from riverine to lacustrine spawning. Three genomic clusters were revealed, of which two refer to the riverine and lacustrine spawners within the flock of Sevan trouts (with FST value = 0.069). A few SNP outliers under selection were discovered that could be responsible for assortative mating based on visual recognition. The Holocene climatic oscillations and the desiccation of tributaries could have played an important role in the origin of lacustrine spawning. The relationships between lacustrine ecomorphs were not yet fully resolved. This radiation warrants further investigation.
Cytosolic distribution of six essential elements and nonessential Cd among biomolecules of different molecular masses was investigated in the intestine of brown trout (Salmo trutta) from the karst ...Krka River and Prussian carp (Carassius gibelio) from the lowland Ilova River. Fish were sampled at two locations (reference and contaminated) and in two seasons (autumn and spring). Analyses were conducted by size exclusion high performance liquid chromatography and high resolution inductively coupled plasma mass spectrometry. Although studied salmonid and cyprinid fish have different biological characteristics, obtained profiles often showed mostly similar patterns in both species. Specifically, Cd and Cu were dominantly bound to metallothioneins in both species, but the same association was not observed for Zn, whereas Mo distribution was similar in the intestine of both fish species with two well shaped and clear peaks in HMM (100–400 kDa) and VLMM (2–8 kDa) range. In brown trout, Se was mostly associated with biomolecules of very low molecular masses (VLMM, <10 kDa), whereas significant additional elution in HMM region (30–303 kDa) was observed only in Prussian carp. Iron binding to VLMM biomolecules (1.8–14 kDa) was observed only in brown trouts, and of Zn in Prussian carps. Cobalt was mostly bound to HMM biomolecules (85–235 kDa) in brown trout and to VLMM biomolecules (0.7–18 kDa) in Prussian carp. Comparison of intestinal profiles with previously published data on liver and gills revealed some similarities in distribution, but also organ-specific differences due to the different function and composition of each organ. As so far there is no published data on intestinal trace metal distribution, the obtained results represent the novel findings, and the key point for the exact identification of specific metal-binding biomolecules which could eventually be used as biomarkers of metal exposure or effects.
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•Distribution profiles of Cd, Co, Cu, Fe, Mo, Se and Zn in fish intestinal cytosol•Comparison of distribution of trace elements in brown trout and Prussian carp•Strong association to metallothioneins observed for Cd and Cu.•Co, Fe, Se and Zn showed some considerable species-specific differences.•Tissue-specific differences due to the different function and composition of organs
•Patterns of Austrian brown trout production for stocking purposes are reviewed.•Hybridized broodstocks of local and non-local origin are reared, domesticated and widely distributed.•Stocking ...potentially weakens wild populations through genetic introgression.
In spite of growing evidence pointing to ecological and genetic risks to wild fish populations, artificial propagation and stocking remain common practices for recreational fishery management. Moreover, even a cursory level of monitoring and evaluation of these risks is neglected, especially where fisheries are managed by private entities. Against this backdrop and with the goal of establishing a more integrated system of ecosystem-based management, this study aims to identify potential threats from the current practices and patterns of brown trout management in Austria. We surveyed 26 private brown trout hatchery operations in three Austrian provinces to examine and categorize the practices in the production of brown trout for stocking. Specifically, we examined the rearing practices and the “trading networks” among trout farmers for characteristics such as rearing history, operating principles, broodstock origins and maintenance, and output figures. Several risk-associated practices emerged, including introduction of brood from divergent lineages outside of Austrian watersheds, translocation and mixing of fish across major watersheds within Austria, and reinforced domestication across multiple generations of captivity. These practices jeopardize native populations by disrupting local adaptations resulting from mixing of native and non-native lineages, reducing genetic diversity within lineages from population bottlenecks, and lowering success of wild populations from domestication selection within the hatchery environment. The findings, which identify threats rather than directly measure impacts, are discussed within the context of concerns on the role of conserving intraspecific diversity for native brown trout fisheries. We conclude by suggesting the integration of ecological and genetic principles into propagation and stocking practices to achieve fishery management strategies more compatible with maintaining natural diversity and adaptive potential of brown trout in Austria.
Abstract The thermotactic response of brown trout ( Salmo trutta ) was examined with the goal to investigate potential effects of the emerging temperature-dependent fatal trout disease PKD ...(proliferative kidney disease). First the differences in cold-water preferences of two forms of brown trout, lacustrine (migratory) and riverine, were determined. Second, it was studied whether this preference was changed in fish infected with PKD. The experiment involved a one-week habituation period at 14 °C in a two-chamber runway followed by a week of 3 °C temperature difference between the two runways. The fish could freely move between lanes via an opening at the end where food was provided. The temperature manipulation was repeated twice, and there were 3 trials per experimental group. All fish developed a clear spatial preference in the test. Lacustrine trout demonstrated a preference for warmer water, while riverine trout preferred cooler water. This may increase the risk to PKD in the lacustrine form. Most strikingly, riverine trout experimentally exposed to Tetracapsuloides bryosalmonae , the parasite that causes PKD, demonstrated stronger cold-seeking behaviour than control fish. Cold seeking behaviour suggests the occurrence of a disease-induced behavioural chill response, which may play an important role in disease recovery. This demonstrates the significance of protecting river connectivity and cold-water sanctuaries as management strategies for preserving salmonid populations in a warming climate.
