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

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.

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

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f95-024 ◽

1995 ◽

Vol 52 (2) ◽

pp. 243-251 ◽

Cited By ~ 59

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.

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Parr–Smolt Transformation of Yearling Atlantic Salmon (Salmo salar) at Several Rearing Temperatures

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f81-160 ◽

1981 ◽

Vol 38 (10) ◽

pp. 1189-1198 ◽

Cited By ~ 67

Author(s):

C. E. Johnston ◽

R. L. Saunders

Keyword(s):

Atlantic Salmon ◽

Atpase Activity ◽

Salmo Salar ◽

Salinity Tolerance ◽

Elevated Temperatures ◽

Salt Water ◽

Effect Of Temperature ◽

Atlantic Salmon Salmo Salar ◽

Thermal Effluent ◽

Thermal Regimes

Six different rearing conditions were used to study the effect of temperature on seasonal changes in growth, condition factor, body silvering, body moisture and lipid content, salinity tolerance, and gill Na–K-ATPase activities of laboratory and pond-reared yearling Atlantic salmon (Salmo salar). Growth during the winter was greatest at the highest rearing temperature (16 °C) whereas those under simulated natural conditions grew slowest. Increasing temperatures in the spring stimulated growth more than constant temperature. Based on increased salinity tolerance, elevated ATPase activity, and growth in salt water, smolt development proceeded at all temperatures up to 16 °C. More smolts were produced in the high thermal regimes resulting in the best growth and the largest proportion of fish reaching smolt size. Unlike some Pacific salmonids, Atlantic salmon develop smolt status at temperatures as high as 16 °C. Yearling smolts can be produced at elevated temperatures and the use of thermal effluents for this purpose is promising.Key words: smoltification, smolt criteria, salinity tolerance, ATPase activity, rearing temperatures, elevated thermal regimes, thermal effluent, Salmo salar

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Contrasts in development and smolting of genetically distinct sympatric anadromous and nonanadromous Atlantic salmon, Salmo salar

Canadian Journal of Zoology ◽

10.1139/z91-289 ◽

1991 ◽

Vol 69 (8) ◽

pp. 2075-2084 ◽

Cited By ~ 17

Author(s):

Tim P. Birt ◽

John M. Green ◽

William S. Davidson

Keyword(s):

Atlantic Salmon ◽

Atpase Activity ◽

Growth Performance ◽

Salmo Salar ◽

Salinity Tolerance ◽

Condition Factor ◽

Chloride Cells ◽

Group Differences ◽

Atlantic Salmon Salmo Salar ◽

Breeding Populations

Parameters associated with the parr–smolt transformation were compared in cultured 1+ anadromous and nonanadromous Atlantic salmon derived from wild broodstock collected in Gambo River, Newfoundland. Progeny of nonanadromous salmon were significantly longer at swim-up than progeny of anadromous salmon, although consistent differences in growth performance were not observed during most of the 1 st year of development. Anadromous salmon grew more rapidly than nonanadromous salmon in the spring months during the smolting period. Distinct differences were noted between groups in seasonal levels of body silvering, gill Na+–K+ ATPase activity, and size and number of gill chloride cells. Most male nonanadromous salmon matured as "post-smolts," whereas maturation was not observed among female nonanadromous nor among either sex in the anadromous group. Differences between anadromous and nonanadromous salmon were not observed in seasonal levels of body moisture, plasma Na+ and Cl−, condition factor, or salinity tolerance. Differences noted between groups are probably genetic in nature and suggest that the two forms of salmon in Gambo River represent separate breeding populations.

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Changes in Gill ATPase Activity and Smolt Status of Atlantic Salmon (Salmo salar)

Journal of the Fisheries Research Board of Canada ◽

10.1139/f78-244 ◽

1978 ◽

Vol 35 (12) ◽

pp. 1542-1546 ◽

Cited By ~ 82

Author(s):

Richard L. Saunders ◽

Eugene B. Henderson

Keyword(s):

Moisture Content ◽

Atlantic Salmon ◽

Atpase Activity ◽

Salmo Salar ◽

Salinity Tolerance ◽

Atlantic Salmon Salmo Salar ◽

Photoperiod Regime ◽

Natural Photoperiod ◽

Salmon Smolt ◽

Photoperiod Manipulation

Gill Na+K+-activated ATPase activity increased during winter–spring in Atlantic salmon (Salmo salar) held at 10 °C and subjected to simulated natural or reciprocal (light/dark ratio opposite that of natural) photoperiods. ATPase activity increased earlier and was greater under the reciprocal than under the natural photoperiod regime. Body lipid decreased and moisture content increased sooner and more sharply in reciprocal than in natural photoperiod fish. Salinity tolerance (to 40‰) increased between March and April. Exposure to 40‰ salinity for periods up to 14 d gave marked increases in ATPase activity over levels measured in freshwater. Gill ATPase activity is a sensitive indicator of the ability of Atlantic salmon to osmoregulate in seawater. Together with lipid-moisture content, tolerance to high salinity, and migratory behavior, gill ATPase activity provides a valid indication of smolt readiness to migrate to sea. Key words: smolt criteria, photoperiod manipulation, Atlantic salmon, smolt physiology, salinity tolerance, osmoregulation

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Effects of Increases in Freshwater Temperature on Loss of Smolt Characteristics in Atlantic Salmon (Salmo salar)

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f91-022 ◽

1991 ◽

Vol 48 (2) ◽

pp. 164-169 ◽

Cited By ~ 54

Author(s):

J. Duston ◽

R. L. Saunders ◽

D. E. Knox

Keyword(s):

Atlantic Salmon ◽

Atpase Activity ◽

Salmo Salar ◽

Salinity Tolerance ◽

Plasma Osmolality ◽

Inorganic Phosphorus ◽

Control Group ◽

Atlantic Salmon Salmo Salar ◽

Natural Photoperiod ◽

And Control

Two-year-old (2+) Atlantic salmon (Salmo salar) raised under ambient temperature and simulated natural photoperiod (45°N) completed smolting between February and May, exhibiting significant increases in gill Na+, K+-ATPase activity and salinity tolerance (96 h, 37.5 ppt) but no significant changes in plasma osmolality. On May 2 the smolts were divided into four groups (each n = 80) and subjected to a rapid (2–3 h) increase in temperature from ambient (5 °C) to 10, 13, or 16 °C or remained ambient (control) which rose to 12 °C by the end of the experiment on June 5. In the 10, 13, and 16 °C groups, mean gill Na+, K+-ATPase activity (micromoles inorganic phosphorus per milligram protein per hour) declined significantly from 6.6 units on May 2 to 4.3, 3.6, and 2.3 units, respectively, on May 23. In the control group, Na+, K+-ATPase activity showed no significant changes during the study. Plasma osmolality was maintained in all groups between 290 and 304 mosmol∙kg−1. Salinity tolerance tests revealed a significant decline in survival in the 16 °C group from May 2 and in the 10 °C, 13 °C, and control groups from May 13, but no significant differences were observed among the three groups. The results support the hypothesis that increases in freshwater temperature accelerate the loss of hypoosmoregulatory capacity.

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Temperature-related loss of smolt characteristics in Atlantic salmon (Salmo salar) in the wild

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f99-099 ◽

1999 ◽

Vol 56 (9) ◽

pp. 1649-1667 ◽

Cited By ~ 51

Author(s):

Stephen D McCormick ◽

Richard A Cunjak ◽

Brian Dempson ◽

Michael F O'Dea ◽

Judith B Carey

Keyword(s):

Atlantic Salmon ◽

Atpase Activity ◽

Salmo Salar ◽

Salinity Tolerance ◽

Connecticut River ◽

Atlantic Salmon Salmo Salar ◽

Penobscot River ◽

In The Wild ◽

Higher Temperature ◽

Negative Impacts

Atlantic salmon (Salmo salar) that had previously been released as fry in tributaries of the Connecticut River were captured from 1993 to 1997 during their normal spring smolt migration 198 km from the mouth of the river. Smolts had peak levels of gill Na+,K+-ATPase activity and salinity tolerance early in migration (early May), indicating physiological readiness to enter seawater. Significant decreases in gill Na+,K+-ATPase activity (29-66%) and salinity tolerance were seen in smolts at the end of the migratory period (late May and early June). Reduced gill Na+,K+-ATPase activity occurred earlier in warm years and was directly related to the degree-days during migration (r2 = 0.75). Reduced gill Na+,K+-ATPase activity was found at the end of migration in warmer, southern rivers (Connecticut River and Penobscot River, Maine) but not in northern rivers (Catamaran Brook, New Brunswick, and Conne River, Newfoundland). Both hatchery- and stream-reared fish held in the laboratory exhibited a more rapid loss of physiological smolt characteristics when held at higher temperature. The results indicate that late migrants in southern rivers lose physiological smolt characteristics due to high temperatures during spring migration. Delays in migration, such as those that occur at dams, may have negative impacts on smolt survival in warmer rivers.

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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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Methods for Nonlethal Gill Biopsy and Measurement of Na+, K+-ATPase Activity

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f93-075 ◽

1993 ◽

Vol 50 (3) ◽

pp. 656-658 ◽

Cited By ~ 695

Author(s):

Stephen D. McCormick

Keyword(s):

Atlantic Salmon ◽

Atpase Activity ◽

Salmo Salar ◽

Salinity Tolerance ◽

Fish Species ◽

Detrimental Effect ◽

Physiological Ecology ◽

Gill Tissue ◽

Atlantic Salmon Salmo Salar ◽

Juvenile Atlantic Salmon

A gill biopsy, in which a small portion of gill tissue was removed from anesthetized fish, was shown to have no detrimental effect on subsequent survival, growth, and salinity tolerance of juvenile Atlantic salmon (Salmo salar). A method for measurement of Na+, K+ -ATPase activity in this small amount of gill tissue is presented. These methods are useful for nonlethal monitoring of physiological smolt characteristics in salmonids and may have applications in the study of disease, toxicology, and physiological ecology of many fish species.

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