Efforts to aid downstream migrating brown trout (Salmo trutta L.) kelts and smolts passing a hydroelectric dam and a spillway
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Brown trout
Spillway
Hatchery
Ditch
Smoltification
Many salmonids, including brown trout ( Salmo trutta), demonstrate alternative migration strategies under different environmental conditions, and as such, they are assumed to be predominantly facultative. Through experimental breeding for two generations, we produced purebred, crossed, and backcrossed groups of phenotypically resident, migratory, and hybrid strains of brown trout originating from a single watershed, and raised them in common-garden conditions. We examined the spring smolt migration tendency of the crosses in outdoor circular channels using passive integrated transponder telemetry at ages 2 and 3 years and found consistent and individually repeatable interstrain differences in migration distance and migration activity. The crossbred fish displayed intermediate behaviour, while later release to the migration channels with food augmentation affected the temporal dynamics of migration but not the total distances migrated. Migration tendency was positively associated with physiological smoltification and fish growth metrics. These results show that some earlier results interpreted as phenotypic plasticity may instead reflect genetic differences within and among populations. The intrinsic differences in reaction norms for both growth and migration tendency require novel management attention for effective conservation strategies.
Brown trout
Smoltification
Introgression
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Prey consumption rates of piscivorous brown trout Salmo trutta were studied in the Pasvik watercourse, which forms the border between Norway and Russia. Estimates of food consumption in the field were similar to or slightly less than maximum values from a bioenergetic model. The piscivore diet consisted mainly of vendace Coregonus albula with a smaller number of whitefish Coregonus lavaretus . Individual brown trout had an estimated mean daily intake of c . 1·5 vendace and 0·4 whitefish, and a rapid annual growth increment of 7–8 cm year −1 . The total population of brown trout >25 cm total length was estimated as 8445 individuals (0·6 individuals ha −1 ), giving a mean ± s . e . annual consumption of 1553880 ± 405360 vendace and 439140 ± 287130 whitefish for the whole watercourse. The rapid growth in summer of brown trout >25 cm indicated a high prey consumption rate.
Coregonus lavaretus
Brown trout
Piscivore
Subarctic climate
Coregonus
Bioenergetics
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At the southern European edge of Atlantic salmon ( Salmo salar ) distribution, all the hybrids found in nature are the product of crosses between female salmon and male brown trout ( Salmo trutta ). By artificially producing reciprocal crosses between salmon and trout, we demonstrate that unidirectional hybridization observed in nature is the result of postzygotic barriers that produce very high mortality rates (95%) in female trout × male salmon hybrids and not the consequence of prezygotic isolation or behavioural differences between the two species. Mortality of female trout × male salmon hybrids mainly occurs during the last phases of development, and a high percentage of these surviving hybrids showed external deformities that could compromise survival in the wild. Another important finding is the existence of paternal factor in embryo development. Using time to midhatch as an indicator of developmental rate, female salmon × male trout hybrids hatched faster than female trout × male salmon hybrids, with both developing at a rate intermediate to the pure crosses. The early emergence of female salmon × male trout hybrids, which have similar survival to pure salmons, could have fitness repercussions, since early emerging fry have a competitive advantage over later emerging fry.
Brown trout
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This study was conducted to test the hypothesis that redd superimposition by salmonine fishes is a consequence of limited habitat availability. We monitored redd site selection by brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta) for two spawning seasons in Valley Creek, Minnesota. Redd superimposition rates were high; over one half of the brook trout and one third of the brown trout superimposed redds. We tested the role of habitat availability in this process by characterizing microhabitat at sites with and without redds in four small sections of this stream and then determined whether superimposition could be explained by random dispersal of fish over available habitat. Brown trout preferred spawning sites with high flows whereas brook trout strongly preferred deep sites with upwelling groundwater. No relationship was observed between fish density and superimposition. Additionally, the observed frequency of superimposition was greater than expected by chance in six of eight instances for brown trout and in one of three instances for brook trout. Finally, a behavioral experiment provided direct evidence that females have a behavioral preference to spawn on existing redd sites, suggesting that factors other than habitat may determine redd site selection and hence superimposition.
Brown trout
Fontinalis
Superimposition
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Administration of flumequine to brown trout S a h o trutta and Atlantic salmon Salmo salar, using bath treatments, resulted in significant serum levels of the antibiotic.Bath concentrations of 50. 100 and 500 ppm were tested for up to 5 h.Temperature, pH, and calcium hardness of the bath water were all found to influence serum levels achieved, as did the level of the drug in the bath.Following bath treatment, serum levels of flumequine greater than the minimum inhibitory concentrations for most susceptible fish pathogens were maintained for up to 14 d.Flumequine serum levels eliciting a toxic response in treated fish were determined.The efficacy of flumequine bath treatments in the control of furunculosis, caused by Aeromonas salmonicida, has been established and its application as both a prophylactic and a chemotherapeutic method for the control of bacterial infections is proposed.
Brown trout
Flumequine
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Smoltification
Massif
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Abstract The aim of this study was to determine and compare the phenotypic variation in Çoruh trout ( Salmo coruhensis ), Rize trout ( Salmo rizeensis ), brown trout ( Salmo trutta fario ) and their native hybrids ( S. rizeensis × S. t. fario ; S. t. fario × S. coruhensis ; S. rizeensis × S. coruhensis ). The numbers and diameters of red and black spots were determined on operculum, fins and above and below the lateral line. The results from this study indicate that there were differences in spotting pattern, colour pattern or fin pigmentation traits between S. rizeensis , S. t. fario , S. coruhensis and their hybrids. Consequently, native S. rizeensis , S. t. fario and S. coruhensis were affected by interaction and phenotypic plastic aspects of traits in S. rizeensis were dominant in their hybrids ( S. rizeensis × S. t. fario ; S. rizeensis × S. coruhensis ).
Brown trout
Operculum (bryozoa)
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This study was conducted to test the hypothesis that redd superimposition by salmonine fishes is a consequence of limited habitat availability. We monitored redd site selection by brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta) for two spawning seasons in Valley Creek, Minnesota. Redd superimposition rates were high; over one half of the brook trout and one third of the brown trout superimposed redds. We tested the role of habitat availability in this process by characterizing microhabitat at sites with and without redds in four small sections of this stream and then determined whether superimposition could be explained by random dispersal of fish over available habitat. Brown trout preferred spawning sites with high flows whereas brook trout strongly preferred deep sites with upwelling groundwater. No relationship was observed between fish density and superimposition. Additionally, the observed frequency of superimposition was greater than expected by chance in six of eight instances for brown trout and in one of three instances for brook trout. Finally, a behavioral experiment provided direct evidence that females have a behavioral preference to spawn on existing redd sites, suggesting that factors other than habitat may determine redd site selection and hence superimposition.
Brown trout
Fontinalis
Superimposition
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By combining behavioural observations on adult resident brown trout Salmo trutta in the laboratory with radio telemetry studies in a natural stream, information on movement and space use in relation to social status was obtained. Dominant individuals moved longer distances and also tended to have larger home ranges than subordinates during the summer. In general, home ranges were larger during daytime than at night. Fish were not strictly territorial since the average overlap in interquartile range was 36% during the summer. During the spawning period, the brown trout moved to specific spawning areas resulting in an increased overlap (89%) in space use. Subordinate individuals now tended to increase both home range and interquartile range and were also less frequently observed in spawning areas relative to dominants.
Brown trout
Home range
Dominance (genetics)
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Smoltification
Axial skeleton
Skeleton (computer programming)
Morphology
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