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.

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.

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.

Hydroacoustic monitoring of fish in sea cages: target strength (TS) measurements on Atlantic salmon (Salmo salar)

2004 ◽  
Vol 69 (2) ◽  
pp. 205-209 ◽  
Author(s):  
F.R. Knudsen ◽  
J.E. Fosseidengen ◽  
F. Oppedal ◽  
Ø. Karlsen ◽  
E. Ona
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Target Strength ◽  
Atlantic Salmon Salmo Salar

Effects of size and spring growth on sexual maturation in 1+ Atlantic salmon (Salmo salar) male parr: interactions with smoltification

1995 ◽  
Vol 52 (12) ◽  
pp. 2682-2694 ◽  
Author(s):  
Ingemar Berglund
Keyword(s):  
Growth Rate ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Sexual Maturation ◽  
Food Restriction ◽  
High Growth ◽  
High Growth Rate ◽  
Early Summer ◽  
Fish Length ◽  
Atlantic Salmon Salmo Salar

Individually identified 1-year-old Atlantic salmon (Salmo salar) parr of Baltic origin were subjected to four different restricted feeding regimes during May and June, and the effects of feeding regime and fish length on the probability of sexual maturation in males were evaluated using logistic regression. Food restriction in June decreased specific growth in weight during June to ca. 22% of that in the control. On average, the maturation rate was reduced from 60% in controls to 48, 45, and 36% in groups on restricted rations. Furthermore, the positive effect of initial length on the probability of maturation was depressed in groups on restricted food in June or May and June. The results of this study show that food restriction in spring has a significant negative effect on the probability of maturation in male salmon parr, but maturation seems to be suppressed in only a small part of the experimental populations. The occurrence of maturing males among fish with a very low or negative growth rate during June and poor condition by the end of June implies, however, that high growth rate in June is not necessary for the onset of rapid gonadal growth in early summer.

Fecundity of Atlantic Salmon (Salmo salar) from Two Maine Rivers

1971 ◽  
Vol 28 (5) ◽  
pp. 764-767 ◽  
Author(s):  
E. T. Baum ◽  
A. L. Meister
Keyword(s):  
Body Weight ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Total Body Weight ◽  
Body Cavity ◽  
The Body ◽  
Fish Length ◽  
Atlantic Salmon Salmo Salar ◽  
Significant Difference ◽  
Total Body

Estimates of numbers of eggs in 164 hatchery-spawned Atlantic salmon (Salmo salar) from two Maine rivers ranged from 3528 to 18,847, and egg number per pound of total body weight from 523 to 1385. Sample autopsies of 10 salmon revealed that artificial spawning removed an average of more than 97% of the eggs in the body cavity. There was no significant difference between von Bayer and displacement estimates of fecundity. Valid estimates of the potential egg deposition of Atlantic salmon runs in the two Maine rivers studied can be made using routinely collected trapping data and the regression formulae based on fish length resulting from this study. Salmon that spent 2 years at sea before spawning contained lower total numbers of eggs but appeared to have a higher rate of fecundity than older fish. Factors governing egg size could not be isolated. Loss in body weight during spawning is discussed.

Microstructure and texture of fresh and smoked Atlantic salmon, Salmo salar L., fillets from fish reared and slaughtered under different conditions

2001 ◽  
Vol 32 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Sjofn Sigurgisladottir ◽  
Margret S. Sigurdardottir ◽  
Helga Ingvarsdottir ◽  
Ole J. Torrissen ◽  
Hannes Hafsteinsson
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Atlantic Salmon Salmo Salar

Persistence of Orally Administered Salmonella enterica Serovars Agona and Montevideo in Atlantic Salmon (Salmo salar L.)

2005 ◽  
Vol 68 (7) ◽  
pp. 1336-1339 ◽  
Author(s):  
L. L. NESSE ◽  
T. LØVOLD ◽  
B. BERGSJØ ◽  
K. NORDBY ◽  
C. WALLACE ◽  
...  
Keyword(s):  
Gastrointestinal Tract ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Salmonella Enterica ◽  
Most Probable Number ◽  
Fish Feed ◽  
Internal Organs ◽  
Probable Number ◽  
Atlantic Salmon Salmo Salar ◽  
Gastric Intubation

The objective of our experiments was to study the persistence and dissemination of orally administered Salmonella in smoltified Atlantic salmon. In experiment 1, salmon kept at 15°C were fed for 1 week with feed contaminated with 96 most-probable-number units of Salmonella Agona per 100 g of feed and then starved for 2 weeks. Samples were taken from the gastrointestinal tract and examined for Salmonella 1, 2, 8, 9, 15, and 16 days after the feeding ended. In experiment 2, Salmonella Agona and Montevideo were separately mixed with feed and administered by gastric intubation. Each fish received 1.0 × 108, 1.0 × 106, or 1.0 × 104 CFU. The different groups were kept in parallel at 5 and 15°C and observed for 4 weeks. Every week, three fish in each group were sacrificed, and samples were taken from the skin, the pooled internal organs, the muscle, and the gastrointestinal tract and examined for the presence of Salmonella. The results from the two experiments showed that the persistence of Salmonella in the fish was highly dependent on the dose administered. Salmonella was not recovered from any of the fish that were fed for 1 week with the lowest concentration of Salmonella. In the fish given the highest dose of Salmonella, bacteria persisted for at least 4 weeks in the gastrointestinal tract as well as, to some extent, the internal organs. The present study shows that under practical conditions in Norway, the risk of Salmonella in fish feed being passed on to the consumer of the fish is negligible.

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