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.

Influence of fluoride on aluminum toxicity to Atlantic salmon (Salmo salar)

1995 ◽  
Vol 52 (11) ◽  
pp. 2432-2444 ◽  
Author(s):  
Steven J. Hamilton ◽  
Terry A. Haines
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Aluminum Toxicity ◽  
Gill Tissue ◽  
Fish Length ◽  
Aluminum Exposure ◽  
Fluoride Treatment ◽  
Atlantic Salmon Salmo Salar ◽  
Secondary Lamellae ◽  
Gill Lamellae

Atlantic salmon (Salmo salar) alevins were exposed to various aluminum (0–4700 μg/L) and four fluoride (0–500 μg/L) concentrations at two pH values (5.5 and 6.5) for 4- and 30-d periods. In the 4-d tests, aluminum with fluoride was less toxic at pH 6.5 than at pH 5.5, whereas without fluoride, pH had no effect. In the 30-d test, mortality in all treatments was 17–21% at pH 5.5, but only 3–7% at pH 6.5. Fish length and weight after 30 d were reduced in all fluoride–aluminum treatments at pH 5.5, but only in the 200-μg/L aluminum without fluoride treatment at pH 6.5. At pH 5.5 and 6.5 without aluminum, histomorphological examinations revealed no abnormalities in gill tissue. However, in aluminum exposure with no fluoride, gill filaments and secondary lamellae were swollen and thickened. Addition of fluoride at pH 6.5 alleviated some gill damage. At pH 5.5 and 200 μg/L aluminum, addition of 100 μg/L fluoride reduced swelling of gill lamellae, but 200 μg/L fluoride did not reduce swelling. Low fluoride concentrations (< 100 μg/L) may reduce gill morphological damage in fish exposed to aluminum in acidic waters, whereas high fluoride concentrations (> 100 μg/L) may not reduce aluminum-induced effects.

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.

Effects of Oceanic Variations and the West Greenland Fishery on Age at Maturity of Icelandic West Coast Stocks of Atlantic Salmon (Salmo salar)

1989 ◽  
Vol 46 (1) ◽  
pp. 16-27 ◽  
Author(s):  
Dennis L. Scarnecchia ◽  
Árni Ísaksson ◽  
S. E. White
Keyword(s):  
Time Series ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
West Coast ◽  
Strongly Correlated ◽  
The West ◽  
West Greenland ◽  
Atlantic Salmon Salmo Salar ◽  
The Mean ◽  
Salmon Fishery

Investigations were conducted on the effects of oceanic variations (as measured by sea temperatures) and catches by the West Greenland salmon fishery on the sea age composition of Atlantic salmon (Salmo salar) stocks from 21 Icelandic west coast rivers. Annual ratios of grilse to two-sea-winter (2SW) salmon were strongly correlated among the 21 rivers. All eight rivers with time series extending back before the expansion of the West Greenland fishery showed lower ratios during the earlier period. Only 2 of the 21 rivers, however, had significantly declining ratios over their time series. In addition, for only one river was West Greenland catch significantly related to the ratios (P < 0.05), and for only one river did ratios increase when the expanded West Greenland fishery was active. Overall, the effects of the fishery on stock composition are evidently minimal. The mean April–May temperature when the smolts were to migrate out of rivers was significantly and positively related to subsequent ratios for five of the rivers, which, along with correlations among the ratios, indicated that more rapid growth of smolts in their first summer may have increased the ratios of grilse to 2SW salmon on several rivers.

scholarly journals Interannual changes in recruitment of the Atlantic salmon (Salmo salar) population in the River Oir (Lower Normandy, France): relationships with spawners and in-stream habitat

2005 ◽  
Vol 62 (4) ◽  
pp. 695-707 ◽  
Author(s):  
Jean-Luc Baglinière ◽  
Frédéric Marchand ◽  
Vincent Vauclin
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Survival Rates ◽  
Stream Habitat ◽  
Juvenile Salmon ◽  
Strongly Correlated ◽  
Data Set ◽  
Atlantic Salmon Salmo Salar ◽  
Salmon Population ◽  
The Mean

Abstract Since 1985, the dynamics of the Atlantic salmon (Salmo salar) population in the River Oir, a spawning tributary of the River Sélune (Lower Normandy, France), have been studied from a data set of parr density and the number and the age structure of migrating fish (smolts and adults). Parr densities (1.5–17.4 per 100 m2) and smolt production (0.25–9.2 per 100 m2) varied considerably from year to year. Migrating juveniles were mainly 1 year old. Abundance of parr and smolts was strongly correlated with 0+ densities. Egg-to-smolt survival rates were highly variable year on year (0.044–1.07%). During the juvenile freshwater phase, mortality was highest between the egg and the 0+ stage (97.5–99.9%). The fluctuations in abundance of juvenile salmon appear to be linked to the number and distribution of spawners within the stream during spawning, and also to the amount of silt deposition on the spawning beds. As a result, mortality was highest during the under-gravel phase, and the mean survival rate from egg to smolt was much lower than in rivers less impacted by human activities. Therefore, during the study period, the low production of smolts during some years might lead to a low renewal rate of the salmon population.

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.

Pathogenesis of Infectious Pancreatic Necrosis in Atlantic Salmon (Salmo salar)

1979 ◽  
Vol 36 (5) ◽  
pp. 587-591 ◽  
Author(s):  
Robert N. Swanson ◽  
James H. Gillespie
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Pancreatic Necrosis ◽  
Virus Concentration ◽  
Live Virus ◽  
Atlantic Salmon Salmo Salar ◽  
Salmon Fry ◽  
Infectious Pancreatic Necrosis ◽  
Low Levels ◽  
Acinar Tissue

Atlantic salmon (Salmo salar) fry and yearling were found to undergo an active but subclinical infection following exposure to infectious pancreatic necrosis (IPN) virus. Eight-week-old Atlantic salmon fry were fed live virus and the mortality and virus concentration in these fry were recorded over a period of 78 d following exposure. Yearling Atlantic salmon were inoculated intraperitoneally with IPN virus and the concentration of virus in the pancreas–intestine, kidneys, spleen, liver, and gonads of inoculated fish was determined over a period of 74 d following inoculation. Virus first appeared in the fry 3 d postinoculation (DPI) and virus titers reached a peak by 8 DPI. Low levels of virus persisted in fry sampled 78 DPI. Virus first appeared in the pancreas–intestine of Atlantic salmon 12 h postinoculation (HPI) and was detected in the kidneys, liver, and spleen by 72 HPI. Peak virus titers were reached in the pancreas–intestine by 72 HPI. Both the pancreas–intestine and kidneys continued to support viral growth frequently and appeared to be important reservoirs of virus. At no time was virus isolated from the gonads of inoculated yearling. Histological examination of yearlings revealed degenerative changes in the pancreatic acinar tissue and in some cases focal necrosis in the liver. No histological abnormalities were found in IPN-infected fry. Key words: infectious pancreatic necrosis, Atlantic salmon, virus, histology

Changes in Mean Weight, Sea-Age Composition, and Catch-per-Unit-Effort of Atlantic Salmon (Salmo salar) Angled in the Godbout River, Quebec, 1859–1983

1986 ◽  
Vol 43 (2) ◽  
pp. 281-287 ◽  
Author(s):  
Alex T. Bielak ◽  
Geoffrey Power
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Age Groups ◽  
Fishing Effort ◽  
Commercial Fisheries ◽  
Catch Per Unit Effort ◽  
Age Composition ◽  
Atlantic Salmon Salmo Salar ◽  
The Mean ◽  
Selective Effects

A weight-age classification, based on recent catches, was retroactively applied to angled Atlantic salmon (Salmo salar) catches recorded in the log of the Godbout salmon club between 1859 and 1983. Over this period, numbers of salmon caught have fluctuated with a periodicity of 20–30 yr but catches have been maintained. There has been a big increase in fishing effort, and the proportion of two-sea-year to previously spawned fish has increased. The mean weight of these age groups has declined 0.005–0.009 kg∙yr−1. These changes are attributed to the selective effects of commercial fisheries on the stock.

Effects of temperature and season on the position holding performance of juvenile Atlantic salmon (Salmo salar)

1985 ◽  
Vol 63 (1) ◽  
pp. 92-96 ◽  
Author(s):  
D. M. Rimmer ◽  
R. L. Saunders ◽  
U. Paim
Keyword(s):  
Atlantic Salmon ◽  
Water Temperature ◽  
Salmo Salar ◽  
Sharp Decrease ◽  
Swimming Velocity ◽  
Water Currents ◽  
Hatchery Fish ◽  
Atlantic Salmon Salmo Salar ◽  
Critical Swimming Velocity ◽  
The Mean

The ability of wild and hatchery yearling Atlantic salmon (Salmo salar) to hold a position against water currents was tested in relation to water temperature and season. This species would not swim, but held positions on the bottom of the test apparatus. Their performance was, therefore, rated on the basis of critical holding velocity instead of critical swimming velocity, often used for other species. Qualitatively, the relationships of critical holding velocity with both temperature and season were similar for wild and hatchery fish. However, wild fish were consistently more able to hold positions against water currents so that the mean water velocities at which they were unable to stem water currents were 25–84% greater than those for hatchery fish. In the winter, the mean water velocities against which both wild and hatchery fish could no longer hold a position were 21.9–50.0% lower than in the summer. Seasonal changes in performance generally increased or decreased with water temperature except in winter when performance declined while water temperature was almost constant. Performance was high and almost unchanging for temperatures above 8 °C, but fell sharply below this temperature. We suggest that the sharp decrease in performance at 8 °C explains the previous observation that this species suddenly moves into the stream bed when temperature falls during the autumn.

Simulation and experimental measurement of side-aspect target strength of Atlantic salmon (Salmo salar) at high frequency

2004 ◽  
Vol 61 (11) ◽  
pp. 2227-2236 ◽  
Author(s):  
Juha Lilja ◽  
Timo J Marjomäki ◽  
Juha Jurvelius ◽  
Tuomo Rossi ◽  
Erkki Heikkola
Keyword(s):  
Atlantic Salmon ◽  
Numerical Simulations ◽  
Salmo Salar ◽  
Geometric Model ◽  
Target Strength ◽  
Species Discrimination ◽  
Fish Length ◽  
Size Estimation ◽  
Atlantic Salmon Salmo Salar ◽  
Simulation Results

Numerical simulations and empirical measurements of swimming Atlantic salmon (Salmo salar) were used to describe the effects of fish behavior on side-aspect target strength (TS). Simulation results were based on the numerical solution of the Helmholtz equation with the finite element method (FEM). A three-dimensional geometric model approximated the shape of the swimbladder of an Atlantic salmon. Numerical simulations were used to study the dependence of TS on the fish length, orientation, and swimming behavior. The results showed strong variation in TS, both when the side-aspect angle was changed and when the swimbladder was bent to the direction of the sonar beam. A total of 11 swimming adult Atlantic salmon 62–107 cm long were measured with a horizontally aimed echosounder (200 kHz) and video camera, and the experimental results were compared with the corresponding simulation results. The linear regression between mean TS and the logarithm of fish length (L, cm) was TS = 24.4log10(L) – 72.9 dB. The strong variability of TS owing to the orientation and bending of the fish and large L/λ ratios reduces the usefulness of TS alone for fish size estimation or species discrimination.

Predation on stocked Atlantic salmon (Salmo salar) fry

2003 ◽  
Vol 60 (1) ◽  
pp. 32-42 ◽  
Author(s):  
J Nathan Henderson ◽  
Benjamin H Letcher
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Salmo Trutta ◽  
Stomach Contents ◽  
Predation Rate ◽  
Predator Species ◽  
Atlantic Salmon Salmo Salar ◽  
Salmon Fry ◽  
Consumption Rates ◽  
Abiotic And Biotic Factors

We studied predator–prey interactions between juvenile Atlantic salmon (Salmo salar) and trout in three Massachusetts, U.S.A., streams and in artificial streams. We sampled stomach contents of age-1+ and older salmon and trout (Salvelinus fontinalis, Salmo trutta) following salmon fry stocking in the spring of 1997 and 1998. Between 4.3 and 48.6% of the stocked fry were consumed within the first 2 days after stocking, and total fry mortality from predation varied from 4.3 to 60.7%. No significant differences were found between stomach weights of predators ( without fry weight) that consumed fry and those that did not. Artificial stream experiments testing effects of habitat complexity and predator species on predator consumption rates revealed that consumption rates were not different between brook (S. fontinalis) and brown (S. trutta) trout (p = 0.59). Predation rate tended to decrease as the percentage of riffle habitat increased but the decrease was not significant (p = 0.22). Our results indicate that predation on stocked Atlantic salmon fry can be substantial (up to 60%), appears to be short lived (2 days), and is not related in a simple way to abiotic and biotic factors.

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