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

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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Parr–Smolt Transformation in Female and Sexually Mature Male Anadromous and Nonanadromous Atlantic Salmon, Salmo salar

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f86-082 ◽

1986 ◽

Vol 43 (3) ◽

pp. 680-686 ◽

Cited By ~ 33

Author(s):

Tim P. Birt ◽

John M. Green

Keyword(s):

Atlantic Salmon ◽

Salmo Salar ◽

Condition Factor ◽

Total Lipid Content ◽

Chloride Cell ◽

Mature Male ◽

Seasonal Patterns ◽

Atlantic Salmon Salmo Salar ◽

Sexually Mature ◽

Mature Male Parr

The parr–smolt transformation was compared in cultured Newfoundland male and female anadromous and nonanadromous Atlantic salmon, Salmo salar. Seasonal patterns of decreasing total lipid content and condition factor accompanied by increasing moisture content, silvering, and branchial Na+-K+ ATPase activity indicate that smoltification occurred only in immature anadromous females. Previously mature anadromous males did not smoitify. In general, smoltification did not occur in nonanadromous salmon. Chloride cell length did not increase in any group with smoltification. The lack of smoltification in previously mature male parr of anadromous stock is consistent with reports of small numbers of male salmon in smolt runs in many Newfoundland rivers.

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

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f85-080 ◽

1985 ◽

Vol 42 (3) ◽

pp. 615-618 ◽

Cited By ~ 56

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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Seawater Adaptation and Parr–Smolt Transformation of Juvenile Atlantic Salmon, Salmo salar

Journal of the Fisheries Research Board of Canada ◽

10.1139/f78-013 ◽

1978 ◽

Vol 35 (1) ◽

pp. 93-100 ◽

Cited By ~ 83

Author(s):

G. J. Farmer ◽

J. A. Ritter ◽

D. Ashfield

Keyword(s):

Moisture Content ◽

Atlantic Salmon ◽

Salmo Salar ◽

Lipid Content ◽

Condition Factor ◽

Fork Length ◽

Temperature Cycle ◽

Seawater Adaptation ◽

Migratory Activity ◽

Atlantic Salmon Salmo Salar

Seawater adaptation of 1- and 2-yr-old Atlantic salmon, Salmo salar, presmolts and smolts was assessed during exposure to salinity increasing from 0.1 to 31‰ by examining changes in the osmotic concentration of their serum, urine, and intestinal fluid. Both age-classes adapted to seawater equally well; the marine osmoregulatory mechanisms apparently function before completion of parr–smolt transformation. Adaptation was possible during the parr stage for fish exceeding 12–13 cm fork length. The timing of transformation was synchronous for 1- and 2-yr-old juveniles as demonstrated by changes in their lipid and moisture content and condition factor (K). Condition factor of juveniles at the Mactaquac Hatchery, New Brunswick (45°58′N), decreased from February until the second half of May, while lipid content decreased from February until the second half of June. Migratory activity of juveniles at this location was maximal during the second half of May coincident with attainment of minimum K values and decreased during the first half of June as K values increased. While timing of changes in lipid and moisture content and K values were similar for juveniles at the Mersey Hatchery, Nova Scotia (44°10′N), lipid content of fish at the more southerly station decreased at a greater rate and migratory activity was apparent earlier. This was probably attributable to the advanced temperature cycle at that location. Smolt-release dates are discussed in terms of the development of the marine osmoregulatory mechanisms and the timing of parr–smolt transformation. Key words: Atlantic salmon, seawater adaptation, parr–smolt transformation, migration, hatchery management

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

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f88-008 ◽

1988 ◽

Vol 45 (1) ◽

pp. 60-64 ◽

Cited By ~ 16

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.

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