Drifters versus residents: assessing size and age differences in Atlantic salmon (Salmo salar) fry

2004 ◽  
Vol 61 (2) ◽  
pp. 273-282 ◽  
Author(s):  
Valérie Bujold ◽  
Richard A Cunjak ◽  
Jason P Dietrich ◽  
David A Courtemanche
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Driving Forces ◽  
Active Movement ◽  
Atlantic Salmon Salmo Salar ◽  
Salmon Fry ◽  
Riverine Habitat ◽  
Life History Patterns ◽  
Young Of The Year ◽  
Set Up

Some young-of-the-year Atlantic salmon (Salmo salar) have a tendency to drift soon after emergence from the gravel, whereas others, called resident fry, set up and defend territories. Little is known about the mechanisms regulating this strong tendency to drift soon after emergence, a phenomenon that can greatly influence survival within a population. This study was carried out in the Western Brook system, Gros Morne National Park, Newfoundland, Canada. The objective was to assess differences, through biometric characteristics, between drifting and resident Atlantic salmon fry by examining both groups of fish caught simultaneously in the same riverine habitat. Resident salmon fry can be up to 4.8% longer and 20.4% heavier compared with drifting fry of similar age (measured in days since emergence). Therefore, it seems that competition, more than prior residence effect, could be part of the driving forces behind this active movement and that differences between subpopulations of Atlantic salmon fry can have major repercussions on life history patterns.

Mechanisms underlying the increase in young-of-the-year Atlantic salmon (Salmo salar) density with habitat complexity

2008 ◽  
Vol 65 (9) ◽  
pp. 1956-1964 ◽  
Author(s):  
Oscar Venter ◽  
James W.A. Grant ◽  
Michelle V. Noël ◽  
Jae-woo Kim
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Habitat Complexity ◽  
Indirect Evidence ◽  
Growth Potential ◽  
Territory Size ◽  
Complex Environments ◽  
Atlantic Salmon Salmo Salar ◽  
Direct Support ◽  
Young Of The Year

We tested three hypotheses used to explain the increase in young-of-the-year (YOY) Atlantic salmon ( Salmo salar ) density with habitat complexity: the territory-size, predator-refuge, and foraging-benefits hypotheses. We manipulated habitat complexity in three different treatments (boulder-removed, control, and boulder-added) at eight sites in Catamaran Brook and the Little Southwest Miramichi River, New Brunswick. The density of juvenile salmon was two times higher in the boulder-added treatment than in the other treatments. Our data were consistent with the territory-size hypothesis; visual isolation was highest and territory size was smallest in the boulder-added treatment, and salmon selected microhabitats to maximize their field of view. Our results showed partial support for the predator-refuge hypothesis; salmon in the boulder-added sites were closer to cover and showed a reduced reaction distance to a novel stimulus, but did not preferentially select microhabitats closer to cover. We found no direct support for the foraging-benefits hypothesis; however, there is indirect evidence that boulders may improve the growth potential of instream habitat. Our results suggest that YOY Atlantic salmon may be attracted to complex environments for the increased cover and that the decreased visibility of these sites causes a reduction in territory size, allowing a higher density of fish.

Annual variation in size-selective mortality of Atlantic salmon (Salmo salar) fry

2001 ◽  
Vol 58 (6) ◽  
pp. 1187-1195 ◽  
Author(s):  
S P Good ◽  
J J Dodson ◽  
M G Meekan ◽  
D AJ Ryan
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Total Mortality ◽  
Weather Conditions ◽  
Fish Length ◽  
Selective Mortality ◽  
Atlantic Salmon Salmo Salar ◽  
Salmon Fry ◽  
Mean Size ◽  
The Mean

We investigated the size-selective mortality of Atlantic salmon (Salmo salar) fry during two consecutive summers that differed markedly in weather conditions. We sampled fry shortly after emergence in June and at the end of August to compare the distributions of back-calculated body size at hatching by examining otolith microstructure. Size-selective mortality was observed in both summers; however, the direction and strength of mortality differed. During the drought conditions of 1995, selective mortality was relatively weak and directed towards the smaller fry in the population. During the flood conditions of 1996, selective mortality was relatively strong and directed towards the larger fry of the same population. Interannual variability in size-selective mortality contributed to significant differences in the mean size of fry at the end of their first summer of life. Size-selective mortality rates estimated from the shifts in fish length at hatching observed during the first summer of life were comparable with published estimates of total mortality of Atlantic salmon fry, indicating that early mortality may be largely size selective. Mortality associated with hydroclimatic events can select against either small or large fish and is a key determinant of mean size attained by the end of the first summer of life.

Selection of Microhabitat in Summer by Juvenile Atlantic Salmon (Salmo salar)

1987 ◽  
Vol 44 (1) ◽  
pp. 120-129 ◽  
Author(s):  
D. L. Morantz ◽  
R. K. Sweeney ◽  
C. S. Shirvell ◽  
D. A. Longard
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
The Body ◽  
Flow Conditions ◽  
Atlantic Salmon Salmo Salar ◽  
Juvenile Atlantic Salmon ◽  
Salmon Fry ◽  
Study Sites ◽  
Selection Of ◽  
Atlantic Salmon Parr

This study was designed to define the microhabitats selected in summer by juvenile Atlantic salmon (Salmo salar). Curves were developed describing the preference of 880 young salmon for water velocity at the fish's position (nose velocity), mean water column velocity, total water depth, and stream substrate size. Study sites were chosen in six morphologically diverse streams in Nova Scotia and New Brunswick during 1982–84. Of the four variables measured, only nose velocity chosen by both fry and parr was not significantly different among years or rivers. Atlantic salmon fry (< 65 mm) most frequently selected nose velocities between 5 and 15 cm∙s−1, small parr (65–100 mm) between 5 and 25 cm∙s−1 and large parr (> 100 mm) between 5 and 35 cm∙s−1. Apparently, juvenile salmon utilized water depths and stream substrates which varied within tolerable limits according to their availability in conjunction with preferred water velocities. Significant differences in the body shape and size of the pectoral fin of Atlantic salmon parr in different rivers did not influence the selection of nose velocities within the range of flow conditions sampled.

Patterns and correlates of movement and site fidelity in individually tagged young-of-the-year Atlantic salmon (Salmo salar)

2003 ◽  
Vol 60 (2) ◽  
pp. 193-202 ◽  
Author(s):  
Stefán Ó Steingrímsson ◽  
James W.A Grant
Keyword(s):  
Atlantic Salmon ◽  
Habitat Use ◽  
Salmo Salar ◽  
Site Fidelity ◽  
Population Regulation ◽  
Fish Movement ◽  
Population Densities ◽  
Atlantic Salmon Salmo Salar ◽  
Young Of The Year ◽  
Study Sites

The literature on stream fish movement offers diverse views on the patterns (restricted vs. nonrestricted), causes (competition vs. habitat use), and consequences (mobile fish of lower vs. equal fitness) of movement. We tagged 320 young-of-the-year Atlantic salmon (Salmo salar) (30.1–55.3 mm), using relatively noninvasive tagging (elastomers) and recovery (snorkeling) techniques, to test these alternative views. Most fish (mean = 63.8%) stayed in the study sites (10–120 m) throughout their respective study season (28–74 days). Of the resighted fish, 61.8% moved less than 1 m up- or down-stream and only three fish moved more than 10 m, causing extremely leptokurtic movement curves. Movement and site fidelity were weakly affected by habitat use and competition. Fish originally found in slow water moved farther than fish from fast water, whereas fish found at high population densities were more likely to disappear than fish from low densities. Finally, mobile fish grew as fast or faster than more sedentary fish, supporting the idea that movement can be advantageous and is not just a by-product of density-dependent population regulation.

Genetic Divergence of Anadromous and Nonanadromous Atlantic Salmon (Salmo salar) in the River Namsen, Norway

1989 ◽  
Vol 46 (3) ◽  
pp. 406-409 ◽  
Author(s):  
Jukka Vuorinen ◽  
Ole Kristian Berg
Keyword(s):  
Life History ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Genetic Divergence ◽  
Gene Diversity ◽  
Atlantic Salmon Salmo Salar ◽  
Large Numbers ◽  
Salmon Fry ◽  
Strong Founder Effect ◽  
Electrophoretic Data

Anadromous and nonanadromous Atlantic salmon, Salmo salar, coexist in the River Namsen in Norway. We studied genetic divergence between these two life history types by using electrophoretic data from 38 protein loci. Although allele frequencies differed significantly between the types at four loci no fixed allele frequency difference was observed. Nei's genetic distance between the life history types, however, was 0.01 a relatively high value for Atlantic salmon populations. The genetic differences observed between anadromous and nonanadromous salmon accounted for 18.3% of the total gene diversity. The five nonanadromous salmon samples formed two genetically different groups corresponding to the upper and lower ranges of the nonanadromous salmon in the river. The average observed heterozygosity was 3.1% for anadromous and 1.0% for nonanadromous salmon. The low heterozygosity in nonanadromous salmon probably reflects a strong founder effect. Stockings of large numbers of anadromous salmon fry to the upper reaches of the River Namsen have caused no detectable hybridization with nonanadromous salmon. Also downstream migrating nonanadromous salmon have apparently not made any important genetic contribution to the anadromous fish.

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