Timing of Sea-Run Brown Trout (Salmo trutta) Smolt Migration: Effects of Climatic Variation

1993 ◽  
Vol 50 (6) ◽  
pp. 1132-1136 ◽  
Author(s):  
Torgny Bohlin ◽  
Claes Dellefors ◽  
Ulo Faremo
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Close Agreement ◽  
Climatic Variation ◽  
Fish Length ◽  
Degree Days ◽  
Annual Fish ◽  
Small Stream ◽  
Brown Trout Salmo Trutta ◽  
Parameter Values

By trapping seaward migrating smolts of brown trout (Salmo trutta), we analyzed the timing of the run in a small stream in southwestern Sweden (58°N) during 1984–90 in relation to environmental factors. Ninety percent of the smolts were captured during a period of 28.7 d (SD 5.9), with median time ranging from April 26 to May 17. Using polynomial multiple regression, we found a positive relationship between the probability of migration per day and the number of degree-days, change in water level, temperature change during the preceding week, and mean annual fish length. Forty-seven percent of the variation was explained. The predicted probabilities were used to calculate the population fraction migrating per day for the seasons 1984–90. There was a close agreement between the observed and expected daily fraction of migrants. The model, with parameter values based on the observations from 1984–90, was also used to predict the daily migration in 1991. The result indicated that the model accurately predicts the smolt run (R2 = 0.40).

The impact of introduced pike (Esox lucius L.) on allopatric brown trout (Salmo trutta L.) in a small stream

Hydrobiologia ◽  
2014 ◽  
Vol 744 (1) ◽  
pp. 223-233 ◽  
Author(s):  
Trygve Hesthagen ◽  
Odd T. Sandlund ◽  
Anders G. Finstad ◽  
Bjørn O. Johnsen
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Esox Lucius ◽  
Small Stream ◽  
Pike Esox Lucius ◽  
Brown Trout Salmo Trutta ◽  
The Impact

Probability of First Sexual Maturation of Male Parr in Wild Sea-run Brown Trout (Salmo trutta) Depends on Condition Factor 1 yr in Advance

1994 ◽  
Vol 51 (9) ◽  
pp. 1920-1926 ◽  
Author(s):  
Torgny Bohlin ◽  
Claes Dellefors ◽  
Ulo Faremo
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Condition Factor ◽  
Mature Male ◽  
Small Stream ◽  
Late Autumn ◽  
Passive Integrated Transponders ◽  
Brown Trout Salmo Trutta ◽  
Mature Male Parr ◽  
Electric Fishing

In three years, in late autumn, underyearling wild sea-run brown trout (Salmo trutta) in a small stream were captured with electric fishing and tagged with microchips (passive integrated transponders). They were recaptured during the following season either as migrating smolts in a trap or by electric fishing in the stream just after the migration period and during spawning (late autumn). At spawning, they were distinguished as sexually mature male parr or immature juveniles. The smolts were longer and heavier at tagging than the mature male parr and the immature parr, which were similar in initial length and weight. The mature male parr had a significantly higher condition factor at tagging than the immature parr. The probability of parr maturation was positively associated with initial condition factor but not with initial body length. Growth of mature male parr and immature parr was similar in the early season but higher for immature parr in the late season. The result indicated that the choice of strategy was made earlier in life than previously recognized.

Small-scale dispersal and population structure in stream-living brown trout (Salmo trutta) inferred by mark–recapture, pedigree reconstruction, and population genetics

2012 ◽  
Vol 69 (9) ◽  
pp. 1513-1524 ◽  
Author(s):  
Leif Asbjørn Vøllestad ◽  
Dimitar Serbezov ◽  
Arthur Bass ◽  
Louis Bernatchez ◽  
Esben Moland Olsen ◽  
...  
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Isolation By Distance ◽  
Juvenile Fish ◽  
Age Groups ◽  
Small Scale ◽  
Mark Recapture ◽  
Small Stream ◽  
Brown Trout Salmo Trutta ◽  
Mature Fish

Many animals move among habitats, and even small-scale dispersal of individuals between habitat patches may have strong implications for population dynamics and structure. Here, we use long-term mark–recapture data combined with extensive genotyping and parentage assignment to investigate the importance of small-scale location change of resident brown trout ( Salmo trutta ) in a small stream (1500 m). During the first summer, juvenile fish dispersed downstream (mean displacement 200 m), with smaller juveniles dispersing longer distances. Downstream movement was also predominant during the first winter, but older fish moved little. This limited dispersal resulted in a significant isolation-by-distance structure for ages 1 and 2, but not for older age groups or for the mature fish. Individual pairwise relatedness coefficients decreased with waterway distance for mature fish during the 2002 and 2003 spawning seasons, but only weakly. Overall, between-site genetic differentiation was stronger for the younger age classes, and the signal decayed with age, indicating that the genetic structure observed in the stream is mainly driven by spatial aggregation of close relatives.

scholarly journals Study on the fecundity of Salmo trutta fario (Brown trout) in Kashmir

2012 ◽  
Vol 4 (1) ◽  
Author(s):  
Nusrat Rasool ◽  
Ulfat Jan
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Mean Value ◽  
Fish Length ◽  
Gonad Somatic Index ◽  
Brown Trout Salmo Trutta ◽  
Total Fish ◽  
The Right ◽  
Somatic Index ◽  
Salmo Trutta Fario

The study has been carried in the year 2004 and describes fecundity, spawning season and sex ratio of brown trout, Salmo trutta fario. A total of 121 brown trout (67 males and 54 females) were captured by angling. Gonad somatic index (GSI) confirmed that spawning lasted from October to December. The left ovary, with some exceptions, was found to be longer and heavier producing more eggs than the right one. The absolute fecundity of sampled population varied from 527 to 2445 and the relative fecundity had a mean value of 2.56. Fecundity was positively co-related with the total fish length (r=0.865), fish weight (r=0.9426) ovary weight (r=0.952) and ovary length (r=0.845).

Difficulties in Aging Atlantic Salmon (Salmo salar) and Brown Trout (Salmo trutta) from Cold Rivers Due to Lack of Scales as Yearlings

1982 ◽  
Vol 39 (2) ◽  
pp. 321-325 ◽  
Author(s):  
Arne Johan Jensen ◽  
Bjørn Ove Johnsen
Keyword(s):  
Atlantic Salmon ◽  
Water Temperature ◽  
Salmo Salar ◽  
Brown Trout ◽  
Salmo Trutta ◽  
Age Determination ◽  
Considerable Proportion ◽  
Degree Days ◽  
Atlantic Salmon Salmo Salar ◽  
Brown Trout Salmo Trutta

Scales in Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) from two cold Norwegian rivers first appeared when the salmon were 33–34 mm long (total length) and the trout were 35–38 mm long. A considerable proportion of the yearlings did not form scales in years with a low water temperature (less than 1000–1100 degree-days from May to October); these individuals lacked the first annulus in the scales. Scales with five circuli or more seldom occurred. The number of days per year with a water temperature above 6.5 °C was better correlated to the formation of scales in Atlantic salmon than the degree-days. In years when the water temperature exceeded 6.5 °C for more than 70–80 days, only minor errors arose in age determination of the salmon; when the temperature exceeded 6.5 °C for less than 70–80 days, some individuals lacked the first annulus in their scales.Key words: Atlantic salmon, brown trout, age determination, temperature, scale formation

scholarly journals Modelling the factors influencing ontogenetic dietary shifts in stream-dwelling brown trout (Salmo trutta)

2018 ◽  
Vol 75 (4) ◽  
pp. 590-599 ◽  
Author(s):  
Javier Sánchez-Hernández ◽  
Fernando Cobo
Keyword(s):  
Body Length ◽  
Brown Trout ◽  
Salmo Trutta ◽  
Prey Availability ◽  
The Body ◽  
Habitat Characteristics ◽  
Water Current ◽  
Fish Length ◽  
Water Current Velocity ◽  
Brown Trout Salmo Trutta

Biotic and abiotic variables shape ontogenetic trajectories of animals. This study modelled (i) the body length related timing of the ontogenetic switch from aquatic to surface prey and (ii) the impacts of habitat characteristics, prey availability, and fish densities on the relative contribution of surface prey to the overall diet of native brown trout (Salmo trutta). We used individual-based models of dietary data for 170 fish (length range 48–343 mm). There was a high degree of individual variation in the use of surface prey, but logistic regression suggested that the shift from aquatic to surface prey was established at a body length of 81 mm (range 36–127 mm). Results of linear mixed-effects models highlighted the importance of fish length, benthic invertebrates, brown trout density, and water current velocity to the switch to surface prey by riverine brown trout, with fish length being the most influential variable. Our study provides evidence of the importance of ontogeny (intrinsic features of individuals linked to fish length) and individual differences in feeding behaviour to understand water-column use for feeding by stream-dwelling salmonids.

Ecological Significance of Differences in Frequency of White Fin Margins Among Four Brown Trout (Salmo trutta) Populations

1988 ◽  
Vol 45 (7) ◽  
pp. 1304-1309 ◽  
Author(s):  
Trend Taugbøl ◽  
Jostein Skurdal ◽  
Ragnvald Andersen
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Selective Pressure ◽  
Territorial Behavior ◽  
Ecological Significance ◽  
Low Frequencies ◽  
Small Stream ◽  
Sea Trout ◽  
Open Sea ◽  
Brown Trout Salmo Trutta

The frequency of distinct white fin margins was investigated in four brown trout (Salmo trutta) populations, living in the small stream Austadbekken (anadromous and stream resident) and in Lake Selura (lake and stream spawners). The frequency varied within and among populations. White margins were most common among parr and mature residents from Austadbekken. Sea trout had very low frequencies compared with parr and mature residents from the same population. Among stream spawners from Lake Selura (which stay the first 0–2 yr in the stream), white margins were less frequent than in Austadbekken; lake spawners (which spend their entire life in the lake) had even fewer. While a previous author stated that white fin margins were under genetic control, our observations indicate that the environment can affect the coloration. We hypothesize that white fin margins play a role in territorial behavior and are developed strongly where territorial behavior is pronounced, i.e. in stream- and river-dwelling trout. There may be a selective pressure, favoring easily seen signals showing that a territory is occupied so that energy-demanding fights can be avoided. In open sea and estuaries where predators are frequent, conspicuous fin margins may be a disadvantage due to greater predation risks.

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