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.

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.

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.

Hypervitaminosis A in first-feeding fry of the Atlantic salmon (Salmo salar L.)

2002 ◽  
Vol 8 (1) ◽  
pp. 7-13 ◽  
Author(s):  
R. ØRNSRUD ◽  
I. E. GRAFF ◽  
S. HØIE ◽  
G. K. TOTLAND ◽  
G.-I. HEMRE
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Hypervitaminosis A ◽  
Atlantic Salmon Salmo Salar ◽  
First Feeding

First feeding of Atlantic salmon, Salmo salar L., under different photoperiods and light intensities

1990 ◽  
Vol 21 (4) ◽  
pp. 435-441 ◽  
Author(s):  
S. O. STEFANSSON ◽  
R. NORTVEDT ◽  
T. J. HANSEN ◽  
G. L. TARANGER
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Atlantic Salmon Salmo Salar ◽  
First Feeding ◽  
Light Intensities

Importance of the Variation in Life History Parameters of Atlantic Salmon (Salmo salar)

1985 ◽  
Vol 42 (3) ◽  
pp. 615-618 ◽  
Author(s):  
Richard L. Saunders ◽  
Charles B. Schom
Keyword(s):  
Life History ◽  
Atlantic Salmon ◽  
Population Size ◽  
Salmo Salar ◽  
Great Variability ◽  
Mature Male ◽  
Life History Parameters ◽  
Atlantic Salmon Salmo Salar ◽  
Sexually Mature ◽  
Mature Male Parr

Atlantic salmon (Salmo salar) demonstrate great variability in their life history; individuals from a given year-class can spawn during several years and can, therefore, breed with salmon from other year-classes. Atlantic salmon can mature after 1–4 sea-winters and some males mature as parr, during the second through fifth years, before going to sea. Salmon may survive to spawn more than once; some spawn several times. This variability in life history may be a safeguard against loss of small stocks through several successive years of reproductive failure, since nonspawning individuals in the river or at sea could spawn in subsequent years. Spawning populations are frequently quite small. The effective spawning population size may be potentially much larger, however, since members of several year-classes, including sexually mature male parr and anadromous adults of various ages, contribute to spawning. The level of inbreeding may be relatively low, since a number of year-classes, each with different sets of parents, are represented during spawning.

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