The production of brown trout, <i>Salmo trutta</i> in tributaries of the Upper Wye, Wales

Milner, Nigel; Gee, A. S.; Hemsworth, R. J.

doi:10.1111/j.1095-8649.1978.tb03473.x

Cited by 28 publications

(21 citation statements)

References 13 publications

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“…Similar instability was reported for brown trout in tributary streams of the upper River Wye, Wales (Milner et al 1978(Milner et al , 1979. Unstable trout stocks may largely be maintained by immigration.…”

Section: Discussionmentioning

confidence: 53%

“…The extent of immigration may vary considerably between stocks and streams. Allen (1951) found almost no migration of brown trout between specific sampling sites in the Horokiwi Stream, whereas in this study and in other streams considerable immigrations have been observed (Horton 196 1, Mills 1969, Milner et al 1978. However, immigration evidently is an important recruitment process in downstream reaches of streams and migration may provide a mechanism to optimise utilization of the total stream habitat, with trout taking up positions appropriate to their size and territorial requirement.…”

Section: Discussionmentioning

confidence: 87%

“…The annual production of 25.7 gm-2 estimated in this study and the total annual salmonid production from 22.2 to 33.1 gm-2 in Brandstrup bxk (site 1 and 2) and 27.1 gm-2 in Mausing Mdlebxk (Mortensen 1977(Mortensen b, 1978 are higher than the postulated maximum. (1 977) in Shelligan Burn and Milner et al (1978) in the tributary Duhonw of the River Wye, also found higher annual values, 16.3-25.0 gmP2 and 21.5-25.4 gm-', respectively. Therefore there seems to be no reason why salmonid production in streams should be limited to a maximum of about 18 gm-2 yr-' and it may be concluded that many Danish streams exceed this rate of production.…”

Section: Discussionmentioning

confidence: 97%

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Production of trout,Salmo trutta, in a Danish stream

Mortensen

1982

Environ Biol Fish

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SynopsisThe numbers of trout, Salmo trutta, in Granslev A, Denmark, were estimated by the removal method on 18 dates from March 1974 to March 1976. Populations density varied fronl0.39 to 0.74 trout m-' in 1974-75 and from 0.36 to 0.59 m-2 in 1975 and at all times four or five year classes were present. The age structure of the population was unstable and the variable natural survival, immigration into and emigration from the study site could not be separated. An annual growth cycle with the most rapid growth for all year classes taking place from May to early August was found. Statistically significant differences between different years occurred in the growth of the 0, I and I1 age groups, but no evidence of'density-dependent growth was found. The biomass ranged from 35.4 to 9.5 g m 2 . The total mean annual biomass was 22.8 and 14.7 gm-2 in the two years and the I1 group made the greatest contribution, 44 and 48%, respectively. During 1975-76 the mean annual biomass of each year class only was about two-thirds of that in 1974-75. Annual production in the two years was 25.7 (range 24.7-28.5) and 12.6 gm-2 (range 11.7-15.0) and the I1 group accounted for about 46 and 38% of the production. In addition eel, Anguilla anguilla, produced about 0.5 gm-2 yF2. The unstable age structure of the trout population was compared with trout populations from other streams. The importance of immigration as a recruitment process in middle and lower reaches of streams and of migrations as a mechanism to optimise utilization of the total stream habitat, as well as temperature as a factor controlling the growth rate are discussed.

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Section: Discussionmentioning

confidence: 53%

Section: Discussionmentioning

confidence: 87%

Section: Discussionmentioning

confidence: 97%

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Production of trout,Salmo trutta, in a Danish stream

Mortensen

1982

Environ Biol Fish

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“…From 1977 to 1980, migrating spawners were tagged with Carlin or Floy-tags to determine their most upstream position in the tributary during the spawning period. In -1978In and 1980In -1981 were counted and mapped (no. km-') throughout the spawning period in zones A and B.…”

Section: Methodsmentioning

confidence: 99%

Population dynamics of brown trout, Salmo trutta L., in a tributary in Brittany (France): spawning and juveniles

Baglinière

Maisse

Lebail

et al. 1989

Journal of Fish Biology

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The colonization by both resident and migrating spawner populations of brown trout and the characteristics of resident and migrating juveniles derived from the two populations have been studied in a brook and its tributary over 4 years. Resident trout spawns mainly in the upstream part of the brook and migrating trout in the downstream part. There are density and growth variations for the two age classes (0+ and 1 +) ofjuveniles in autumn according to the year and the environment. In the brook, the population of0 + fish increases from downstream to upstream while the density of other age classes decreases. The migrating juvenile population of the brook changes annually and consists mainly of 1s (one summer) individualscorning from the upper part. These individuals migrate generally in autumn and winter while young trout produced in the middle and downstream parts of the brook migrate mainly in the spring. The emigration process of the O + population decreases markedly from upstream to downstream and appears to be independent of the autumn length and sex ratio. In the tributary, most trout are O+ years old, the population structure is different, and no migrating fish is observed. The results are discussed and a colonization strategy of the brown trout population in this brook is suggested.

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“…De plus, les valeurs de G, obtenues sur le ruisseau de Kernec pour ces deux classes d'âge, sont semblables à celles observées par EGGLISHAW et SHACKLEY (1977) sur un ruisseau écossais. Par ailleurs, la valeur souvent élevée des tempé-ratures de l'eau hivernales en Bretagne ne provoque généralement pas d'arrêt de croissance durant l'hiver, à la différence des constations faites dans des régions plus nordiques (EGGLISHAW et SHACKLEY, ibidem;MILNER et al, 1978;ELLIOTT, 1985ELLIOTT, et 1988KELLY-QUINN et BRACKEN, 1988). Cette observation se traduit souvent sur les écailles de la truite de cette région par une délimitation, entre la première et la deuxième année de croissance, visible uniquement par l'augmentation de l'espacement intercirculi (BAGLINIÈREet LE LOUARN, 1987).…”

Section: Analyse De La Croissanceunclassified

La croissance de la truite commune (Salmo trutta L.) sur le bassin de Scorff

Baglinière

Maisse

1990

Bull. Fr. Piscic.

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RÉSUMÉLa croissance de la truite commune (Salmo trutta L.) a été étudiée à partir du suivi de cfnq cohortes âgées de 0-à 2-ans dans quatre milieux différents (Scorff aval et amont, affluent, sous-affluent).D'une manière générale, la taille des truites quel que soit leur âge diminue de l'aval vers l'amont du Scorff et de la rivière à l'affluent et au sous-affluent. Le taux mensuel de croissance G = 2,85 (LnL2 -LnL1)/(T2 -T1) diminue de la première à la troisième année de vie quel que soit l'ordre de drainage. Ce taux de croissance varie suivant le milieu pour les deux premières classes d'âge (0+ et 1 ^ ), cet effet milieu étant relié à la densité de population pour les individus 0+. Le taux de croissance varie également suivant les années mais uniquement chez les plus jeunes truites et cet effet année est relié principalement à la température de l'eau. Un modèle de Von Bertalanffy est proposé pour décrire la relation entre la taille (Lf) et la somme des températures moyennes journalières depuis la date moyenne d'émergence (Tmj) pendant la première année:Les résultats sont discutés et permettent de dégager les faits majeurs intervenant sur la croissance de la truite tout au long d'un cycle jusqu'à la maturation sexuelle.Mots-clés : Température -Croissance -Truite commune -Rivière -France. THE GROWTH OF THE BROWN TROUT (SALMO TRUTTA L.) IN THE BASIN OF SCORFF RIVER SUMMARYThe growth of brown trout (Salmo trutta L.) has been studied with 0^ to 2» year old fish belonging to five cohorts, living in four différent environmental conditions (lower and upper part of River Scorff, a tributary and a subtributary of this river).Size of trout decreases in ail âge classes from the lower to the upper part of the main river, from the main river to the tributary and from the tributary to the subtributary. The monthly growth rate, expressed as G = 2.85 (LnL2 -LnL1)/(T2 -T1), decreases in each environmental condition from the first to the third year of life. Différences in the monthly growth rate according to différent environmental conditions could only be observed in the 0^ and 1-âge classes. For 0+ trout, this effect dépends on population density. In the younger trout population, growth rate changes also from one year to another, depending on the température of the water. The relation between length (Lf) and the sum of degree-days from the mean date of émergence (Tmj) is described for the first year of life. A good corrélation is found for an exponential model: Lf = 106.7 (1 -exp ]).Results are discussed and allow to draw some conclusions on the main factors influencing the growth of brown Trout up to the sexual maturation.

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The production of brown trout, Salmo trutta in tributaries of the Upper Wye, Wales

Cited by 28 publications

References 13 publications

Production of trout,Salmo trutta, in a Danish stream

Production of trout,Salmo trutta, in a Danish stream

Population dynamics of brown trout, Salmo trutta L., in a tributary in Brittany (France): spawning and juveniles

La croissance de la truite commune (Salmo trutta L.) sur le bassin de Scorff

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