Importance of Threshold Length and Photoperiod for the Development of Bimodal Length–Frequency Distribution in Atlantic Salmon (Salmo salar)

1991 ◽  
Vol 48 (11) ◽  
pp. 2163-2172 ◽  
Author(s):  
Ove T. Skilbrei
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Light Stimulus ◽  
Morphological Characteristics ◽  
Continuous Light ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Atlantic Salmon Salmo Salar ◽  
Natural Photoperiod ◽  
Threshold Length

Juveniles of 0 + Atlantic salmon (Salmo salar) were graded in narrow length intervals to test the hypothesis that a threshold length determines the segregation into bimodal length–frequency distributions. In the experiment, 1350 juveniles of an initial length of 70–80 mm were held under different light and temperature conditions. Distinct decreases in temperature for short or long periods did not influence the degree of bimodal segregation and temperature did not, thus, seem to be a winter stimulus for segregation in fish of this size. Transfer of fish from continuous light to natural photoperiod was followed by a segregation in growth rates into lower and upper mode fish. Upper mode fish developed smolt appearance the following spring. Under continuous light the bimodality was weak or absent and these fish did not develop morphological characteristics typical of smolts. It is concluded that the individual decision to enter the upper mode and undergo silvering the following spring is strongly dependent on the length of the fish at the time of the winter light stimulus. Fish smaller than a threshold length of about 75 mm reduce their growth rate in response to the natural photoperiod, while fish above this size enter the upper length–frequency mode.

Growth, Parr–Smolt Transformation, and Changes in Growth Hormone of Atlantic Salmon (Salmo salar) Reared under Different Photoperiods

1991 ◽  
Vol 48 (11) ◽  
pp. 2100-2108 ◽  
Author(s):  
Sigurd O. Stefansson ◽  
Björn Th. Bjömsson ◽  
Tom Hansen ◽  
Carl Haux ◽  
G. Lasse Taranger ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Growth Rate ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Continuous Light ◽  
Plasma Growth Hormone ◽  
Hormone Levels ◽  
Light Regimes ◽  
Atlantic Salmon Salmo Salar ◽  
Natural Photoperiod

Potential 1+ smolts of Atlantic salmon (Salmo salar) were reared under three light regimes: simulated natural photoperiod (LDN), continuous light (LD24:0), or a combination of continuous, low-intensity background light and a superimposed simulated natural photoperiod (dual photoperiod, LDD). Growth rate in freshwater was enhanced by LD24:0 and LDD, and changes associated with smoking (increased salinity tolerance, reduced condition coefficient) were advanced under LD24:0. Plasma growth hormone levels were initially high on LD24:0 and LDD whereas on LDN, plasma growth hormone levels increased gradually from February through April. Overall GH levels were negatively correlated with condition coefficient during the final stages of smoking. After 16 mo in seawater, there were no significant size differences among the groups. The incidence of sexual maturation as postsmolts was higher in the LD24:0 and LDD groups whereas the incidence of grilsing was higher in LDN. Results demonstrate the significant influence of photoperiod on growth and smoking in Atlantic salmon. An abrupt increase to continuous light in winter may be sufficient to advance important aspects of the parr–smolt transformation. Dual photoperiod may be a way to combine the increased growth rate observed under continuous light and the normal parr–smolt transformation associated with natural photoperiod.

Development of salinity tolerance in underyearling smolts of Atlantic salmon (Salmo salar) reared under different photoperiods

1995 ◽  
Vol 52 (2) ◽  
pp. 243-251 ◽  
Author(s):  
Åse I. Berge ◽  
Arne Berg ◽  
Trygg Barnung ◽  
Tom Hansen ◽  
Hans Jørgen Fyhn ◽  
...  
Keyword(s):  
Atlantic Salmon ◽  
Atpase Activity ◽  
Salmo Salar ◽  
Salinity Tolerance ◽  
Continuous Light ◽  
Short Photoperiod ◽  
Subsequent Reduction ◽  
Atlantic Salmon Salmo Salar ◽  
First Feeding ◽  
Natural Photoperiod

Groups of Atlantic salmon (Salmo salar), first fed in mid-February 1989, were reared under continuous light (LL) at 12–15 °C until late June. One group remained on LL, while the FEB, MAR, and MAY groups were subjected to segments of a simulated naturally increasing photoperiod (61°N), with initial daylength corresponding to February 1, March 15, and May 1, respectively. The MAR and FEB groups developed important smolt characters (increase in gill Na+,K+-ATPase activity, hypoosmoregulatory ability, and salinity tolerance) during the experiment whereas LL and MAY groups showed only incomplete changes in smolt status. The combination of continuous light during first feeding and early parr stages with a subsequent reduction to short daylength followed by a segment of simulated natural photoperiod allow important parts of the parr–smolt transformation to be completed. The period of exposure to short photoperiod is critical for the synchronization of smolt characters in underyearling Atlantic salmon.

Effects of Constant Day Length on Sexual Maturation and Growth of Atlantic Salmon (Salmo salar) Parr

1988 ◽  
Vol 45 (1) ◽  
pp. 60-64 ◽  
Author(s):  
R. L. Saunders ◽  
E. B. Henderson
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Seasonal Changes ◽  
The Other ◽  
Day Length ◽  
Length Frequency ◽  
Frequency Distributions ◽  
Atlantic Salmon Salmo Salar ◽  
First Feeding ◽  
Sexually Mature

Atlantic salmon (Salmo salar) were reared for 6 mo from first feeding under four photoperiod regimes: LD 12:12, LD 16:8, LD 24:0, and simulated natural (LDN). Water temperature followed seasonal changes but was adjusted so as not to exceed 16 °C in summer or to fall below 6 °C in winter. Growth rates were highest in the LD 24:0 group during the first 3 mo; subsequently, the LD 16:8 fish grew faster than all others. Length–frequency distributions were skewed towards smaller sized fish in January. Sexually mature males were mainly in the lower halves of the length–frequency distributions; females and immature males were distributed throughout. The incidence of mature males was highest in the LDN group (67% of males) but reached high levels (44–58%) in the other groups.

Effects of continuous light and short-day photoperiod on smolting, seawater survival and growth in Atlantic salmon (Salmo salar)

Aquaculture ◽  
1995 ◽  
Vol 130 (4) ◽  
pp. 373-388 ◽  
Author(s):  
Trygve Sigholt ◽  
Magne Staurnes ◽  
Hans J. Jakobsen ◽  
Torbjørn Åsgård
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Continuous Light ◽  
Atlantic Salmon Salmo Salar ◽  
Short Day ◽  
Survival And Growth

Seasonal changes in selected muscle quality parameters in Atlantic salmon (Salmo salar L.) reared under natural and continuous light

2003 ◽  
Vol 9 (3) ◽  
pp. 161-168 ◽  
Author(s):  
U. Nordgarden ◽  
R. Ørnsrud ◽  
T. Hansen ◽  
G.-I. Hemre
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Seasonal Changes ◽  
Continuous Light ◽  
Quality Parameters ◽  
Muscle Quality ◽  
Atlantic Salmon Salmo Salar

Effect of Photoperiods on the Reactions of Juvenile Atlantic Salmon (Salmo salar L.) to Light Stimuli

1963 ◽  
Vol 20 (5) ◽  
pp. 1245-1266 ◽  
Author(s):  
A. T. Pinhorn ◽  
C. W. Andrews
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Light Stimulus ◽  
Continuous Light ◽  
Control Fish ◽  
Intermittent Light ◽  
Exposed Fish ◽  
Juvenile Atlantic Salmon ◽  
Light Stimuli ◽  
Increased Activity

The reactions to light stimuli of juvenile Atlantic salmon exposed to photoperiods (light-exposed fish) and those exposed to control conditions (control fish) were compared. The light-exposed fish showed more activity and reacted more readily to stimuli than the control fish. Both the control and light-exposed fish exhibited a negative phototaxis at all light intensities except the very lowest where a slight positive phototaxis was obvious. The intensity of an intermittent light stimulus had very little effect on the intensity of the reaction in the light-exposed fish, while the control fish showed an increase in the intensity of the reaction with an increase in the intensity of the light stimulus. The control fish showed an increase in the reaction to the intermittent light stimulus the longer the stimulus was applied at the higher levels of stimulation, while the light-exposed fish showed this behavior at the lower levels of stimulation. The reactions to continuous light were similar to the reactions to intermittent light stimuli, but the light-exposed fish reacted more quickly to continuous light than the control fish. These differences in behavior are attributed to the increased activity and sensitivity of the light-exposed fish, resulting from their exposure to photoperiods.

A moving light stimulus elicits a sustained swimming response in farmed Atlantic salmon, Salmo salar L.

2011 ◽  
Vol 37 (2) ◽  
pp. 317-325 ◽  
Author(s):  
Neill A. Herbert ◽  
Sunil Kadri ◽  
Felicity A. Huntingford
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Light Stimulus ◽  
Atlantic Salmon Salmo Salar ◽  
Farmed Atlantic Salmon

Photoperiod Control of Parr–Smolt Transformation in Atlantic Salmon (Salmo salar): Changes in Salinity Tolerance, Gill Na+,K+-ATPase Activity, and Plasma Thyroid Hormones

1987 ◽  
Vol 44 (8) ◽  
pp. 1462-1468 ◽  
Author(s):  
Stephen D. McCormick ◽  
Richard L. Saunders ◽  
Eugene B. Henderson ◽  
Paul R. Harmon
Keyword(s):  
Atlantic Salmon ◽  
Thyroid Hormones ◽  
Atpase Activity ◽  
Salmo Salar ◽  
Salinity Tolerance ◽  
Continuous Light ◽  
Day Length ◽  
Atlantic Salmon Salmo Salar ◽  
First Feeding ◽  
Photoperiod Control

Atlantic salmon (Salmo salar) were subjected to artificial photoperiods to determine the manner and extent of photoperiod control of the parr–smolt transformation. Exposure to continuous light (L24) at first feeding and maintained throughout the rearing period inhibited increases in salinity tolerance and gill Na+,K+-ATPase activity that occurred in spring in fish raised under simulated natural photoperiod (SNP). Fish reared under continuous light and returned to SNP in October (L24OCT) underwent normal increases in salinity tolerance and gill Na+,K+-ATPase activity, whereas those returned in December (L24DEC) underwent delayed and intermediate increases. Plasma thyroxine peaks occurred simultaneously in all groups but were diminished in the L24 and L24DEC groups. Plasma 3,5,3′-triiodo-L-thyronine levels were not affected by any photoperiod treatment. Inhibition of the parr–smolt transformation decreased the potential for growth in seawater. In spite of changes in the timing of the transformation induced by photoperiod treatment, salinity tolerance and gill Na+,K+-ATPase activity were strongly correlated; correlation between changes in salinity tolerance and plasma thyroid hormones were, by comparison, weak. The results demonstrate that continuous light applied early in ontogeny and maintained throughout the rearing period inhibits osmoregulatory changes associated with parr–smolt transformation, whereas increasing day length during winter–spring stimulates transformation.

Effect of 6-, 12-, and 18-month Photoperiod Cycles on Smolting and Sexual Maturation in Juvenile Atlantic Salmon (Salmo salar)

1992 ◽  
Vol 49 (11) ◽  
pp. 2273-2280 ◽  
Author(s):  
J. Duston ◽  
R. L. Saunders
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Sexual Maturation ◽  
Condition Factor ◽  
Temperature Cycle ◽  
Frequency Distributions ◽  
Atlantic Salmon Salmo Salar ◽  
Sexually Mature ◽  
Mature Male Parr ◽  
Modal Group

The results support the hypothesis that the commencement of smolting can occur during the decreasing phase of the annual photoperiod cycle, and sexual maturation during the increasing phase of the cycle, provided individuals have attained certain (unknown) growth thresholds. Thereafter the completion of smolting is entrained by the increasing phase of the photoperiod cycle, and sexual maturation by the decreasing phase. Three groups of Atlantic salmon (Salmo salar) were raised in freshwater for over 2 yr from the eyed egg stage under photoperiod cycles of either 6-, 12- (control), or 18-mo periodicity and an ambient 12-mo temperature cycle. Smolting was judged by changes in salinity tolerance and condition factor. All groups developed bimodal length–frequency distributions by December following hatch. Fish continued to be recruited into the upper modal group (UMG) beyond the shortest day of the photoperiod cycle, providing temperature was not limiting growth. The 6-, 12-, and 18-mo photoperiod cycles resulted in approximately 50, 60, and 100% of the populations being recruited into the UMG. Sexually mature male parr (1 + yr old) occurred only in the lower modal group of the 6- and 12-mo groups.

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