Size-related habitat use in juvenile Atlantic salmon: the importance of intercohort competition

In stream-living salmonids, an underlying mechanism for the critical period after emergence has generally been assumed to be size-dependent swimming capacity constraining fry (age-0) to low-velocity habitats with reduced food availability and intense competition. A further plausible mechanism is that intercohort habitat exclusion confines fry to marginal habitats. This possibility was tested using a seminatural stream with 16 test arenas, each comprising one high-velocity, deep habitat and one low-velocity, shallow habitat. We observed groups of newly emerged Atlantic salmon (Salmo salar) fry, either alone or in sympatry with one or two age-1 salmon. Salmon fry used high-velocity areas (42.2 ± 0.4 cm·s−1) most extensively in the absence of intercohort competition, where they obtained more food than in low-velocity areas (3.3 ± 0.3 cm·s−1), even though foraging efficiency was lower (though not significantly so). In sympatry with older cohorts, fry increased their use of the low-velocity habitat, with a reduced foraging activity, suggesting that strong older cohorts in natural populations may have the potential to influence the strength of the recruiting cohort by negative density dependence due to interference competition for habitat.

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Present Status of the Salmonids Atlantic Salmon and Sea-Trout in the Dutch Part of the River Rhine

Water Science & Technology ◽

10.2166/wst.1994.0057 ◽

1994 ◽

Vol 29 (3) ◽

pp. 37-41 ◽

Cited By ~ 7

Author(s):

W. G. Cazemier

Keyword(s):

Atlantic Salmon ◽

Salmo Trutta ◽

Natural Populations ◽

River Rhine ◽

Sea Trout ◽

The Past ◽

The North ◽

Trout Population ◽

The North Sea ◽

Heavy Pollution

In the past, the anadromous salmonids, Atlantic salmon (Salmo salar) and sea-trout (Salmo trutta), have formed natural populations in the river Rhine. From the beginning of the nineteenth century onwards, the greater part of the drainage area of the river has been gradually altered from a more or less rural and agricultural area, into a highly industrialised one with subsequent industrialisation, river-engineering and heavy pollution. These developments are considered to be the major cause for the disappearance of the populations of anadromous salmonid fish in the 1950s. The water quality has recovered significantly during the past 25 years. From about 1975 onwards, this process gave rise to a recovery of the anadromous trout population. Results of recent studies of the sea-trout migration pattern are presented. They reveal that nowadays these salmonids can complete their up- and downstream migrations from the North Sea to places, situated at hundreds of kilometres upward the river and vica versa. The numbers of recorded Atlantic salmon and catch locations in inland waters are presented. They show a significant increase since 1989. These phenomena can be understood as promising signs of the recovery of the Rhine aquatic ecosystem.

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Detection of effort maximality in adults performing isokinetic wrist flexion and extension

Isokinetics and Exercise Science ◽

10.3233/ies-200274 ◽

2021 ◽

pp. 1-7

Author(s):

Mercè Torra ◽

Eduard Pujol ◽

Anna Maiques ◽

Salvador Quintana ◽

Roser Garreta ◽

...

Keyword(s):

High Velocity ◽

Healthy Male ◽

Wrist Flexion ◽

Low Velocity ◽

Wrist Extensor ◽

Submaximal Effort ◽

The Difference ◽

Muscle Groups ◽

Maximal Effort ◽

Flexion And Extension

BACKGROUND: The difference between isokinetic eccentric to concentric strength ratios at high and low velocities (DEC) is a powerful tool for identifying submaximal effort in other muscle groups but its efficiency in terms of the wrist extensors (WE) and flexors (WF) isokinetic effort has hitherto not been studied. OBJECTIVE: The objective of the present study is to examine the usefulness of the DEC for identifying suboptimal wrist extensor and flexor isokinetic efforts. METHODS: Twenty healthy male volunteers aged 20–40 years (28.5 ± 3.2) were recruited. Participants were instructed to exert maximal and feigned efforts, using a range of motion of 20∘ in concentric (C) and eccentric (E) WE and WF modes at two velocities: 10 and 40∘/s. E/C ratios (E/CR) where then calculated and finally DEC by subtracting low velocity E/CR from high velocity ones. RESULTS: Feigned maximal effort DEC values were significantly higher than their maximal effort counterparts, both for WF and WE. For both actions, a DEC cutoff level to detect submaximal effort could be defined. The sensitivity of the DEC was 71.43% and 62.5% for WE ad WF respectively. The specificity was 100% in both cases. CONCLUSION: The DEC may be a valuable parameter for detecting feigned maximal WF and WE isokinetic effort in healthy adults.

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Studying the Depth Structure of the Kyrgyz Tien Shan by Using the Seismic Tomography and Magnetotelluric Sounding Methods

Geosciences ◽

10.3390/geosciences11030122 ◽

2021 ◽

Vol 11 (3) ◽

pp. 122

Author(s):

Irina Medved ◽

Elena Bataleva ◽

Michael Buslov

Keyword(s):

Seismic Tomography ◽

High Velocity ◽

Fault Zones ◽

Magnetotelluric Sounding ◽

Tien Shan ◽

High Resistivity ◽

Low Velocity ◽

Low Resistivity ◽

Velocity Models ◽

Fluid Saturation

This paper presents new results of detailed seismic tomography (ST) on the deep structure beneath the Middle Tien Shan to a depth of 60 km. For a better understanding of the detected heterogeneities, the obtained velocity models were compared with the results of magnetotelluric sounding (MTS) along the Kekemeren and Naryn profiles, running parallel to the 74 and 76 meridians, respectively. We found that in the study region the velocity characteristics and geoelectric properties correlate with each other. The high-velocity high-resistivity anomalies correspond to the parts of the Tarim and Kazakhstan-Junggar plates submerged under the Tien Shan. We revealed that the structure of the Middle Tien Shan crust is conditioned by the presence of the Central Tien Shan microcontinent. It manifests itself as two anomalies lying one below the other: the lower low-velocity low-resistivity anomaly, and the upper high-velocity high-resistivity anomaly. The fault zones, limiting the Central Tien Shan microcontinent, appear as low-velocity low-resistivity anomalies. The obtained features indicate the fluid saturation of the fault zones. According to the revealed features of the Central Tien Shan geological structure, it is assumed that the lower-crustal low-velocity layer can play a significant role in the delamination of the mantle part of the submerged plates.

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Communications: Water Content of Atlantic Salmon Fry at First Feeding in Southern New Brunswick Hatcheries

The Progressive Fish-Culturist ◽

10.1577/1548-8640(1992)054<0181:cwcoas>2.3.co;2 ◽

1992 ◽

Vol 54 (3) ◽

pp. 181-183 ◽

Cited By ~ 2

Author(s):

R. H. Peterson ◽

A. Sreedharan

Keyword(s):

Atlantic Salmon ◽

New Brunswick ◽

Water Content ◽

First Feeding ◽

Salmon Fry

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SIMULATIONS OF HIGH-VELOCITY CLOUDS. II. ABLATION FROM HIGH-VELOCITY CLOUDS AS A SOURCE OF LOW-VELOCITY HIGH IONS

The Astrophysical Journal ◽

10.1088/0004-637x/753/1/58 ◽

2012 ◽

Vol 753 (1) ◽

pp. 58 ◽

Cited By ~ 8

Author(s):

David B. Henley ◽

Kyujin Kwak ◽

Robin L. Shelton

Keyword(s):

High Velocity ◽

Low Velocity ◽

High Velocity Clouds

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Effect of time of day, time of year, and life history strategy on time budgeting in juvenile Atlantic salmon, Salmo salar

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f99-179 ◽

1999 ◽

Vol 56 (12) ◽

pp. 2397-2403 ◽

Cited By ~ 9

Author(s):

Sveinn K Valdimarsson ◽

Neil B Metcalfe

Keyword(s):

Life History ◽

Atlantic Salmon ◽

Salmo Salar ◽

Life History Strategy ◽

Time Of Day ◽

Life History Strategies ◽

Foraging Efficiency ◽

Atlantic Salmon Salmo Salar ◽

Juvenile Atlantic Salmon ◽

Time Of Year

Traditionally, behavioural studies on juvenile Atlantic salmon, Salmo salar, have been conducted during the day in summer. It is known that Atlantic salmon become nocturnal in winter, but very little is known about their behaviour at that time. Therefore, observations in a seminatural stream were carried out during the day and night, from February to June, comparing diel and seasonal differences in behaviour between fish adopting alternative life history strategies. The results showed a general trend for more activity in spring than in winter, and the fish were found to be foraging at surprisingly low light levels. There were differences in relative feeding rate between the life history strategies; the early migrant fish foraged mostly during the day whereas the delayed migrant fish did more foraging at night. There is some evidence that the early migrant fish made fewer feeding attempts over the winter, which is surprising, since they grow faster over that period. This suggests differences in foraging efficiency, which could contribute to the separation into these two life history strategies.

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