Changes in condition factor and gonadosomatic index in maturing and non-maturing Atlantic salmon (Salmo salar L.) in Bay of Fundy sea cages, and the effectiveness of photoperiod manipulation in reducing early maturation

We provide evidence that in male Atlantic salmon (Salmo salar) parr, maturation is suppressed when mesenteric fat fails to exceed an undefined level by May. In nonmaturing parr the postwinter increase in total lipids began in May, while the mesenteric store started filling in June. However, in male parr which would have matured, total lipids started increasing a month earlier, in April, and the mesenteric store started filling in May. Consequently, maturing male parr had significantly more mesenteric fat than nonmaturing fish by June. Mesenteric fat is needed for maturation. Levels continued to increase in nonmaturing parr during autumn months, but had declined in maturing parr by September. This depletion of mesenteric fat in maturing males coincided with increases in the gonadosomatic index from 0.05 to 10% and with reductions in both feeding and growth. Fasting during spring months delayed increases in total lipids and fat accumulation into the mesenteric store until June and suppressed maturation rates of male parr. The internal decision to suppress maturation is therefore dependent on mesenteric fat levels increasing in May. However, this requires the prior replenishment of other stores in April. A model is proposed to explain the physiological link between fat accumulation during spring and the initiation of maturation.

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Determination of Sexual Maturation Stages of Atlantic Salmon (Salmo salar) Captured at Sea

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f81-057 ◽

1981 ◽

Vol 38 (4) ◽

pp. 405-413 ◽

Cited By ~ 30

Author(s):

D. R. Idler ◽

S. J. Hwang ◽

L. W. Crim ◽

D. Reddin

Keyword(s):

Atlantic Salmon ◽

Salmo Salar ◽

Gonadosomatic Index ◽

Gonadal Development ◽

Maturation Stage ◽

Female Fish ◽

Histological Techniques ◽

Atlantic Salmon Salmo Salar ◽

Placentia Bay

Radioimmunoassay (RIA) of plasma vitellogenin (Vg), estradiol (E2), 11-ketotestosterone (11-keto), and gonadotropin (GtH), together with histological techniques were evaluated for determination of the maturation stage of Atlantic salmon (Salmo salar) at sea.Male salmon had lower plasma Vg, E2, and higher 11-keto levels and could be distinguished from females several months in advance of spawning. Six female salmon were tagged at sea in 1975 in Placentia Bay and samples of blood taken. When the fish were recovered in rivers the lowest plasma Vg value was 396 μg/mL. This formed the basis of a working hypothesis, that fish with Vg values in excess of 396 μg/mL (~5–6 mo before spawning) will spawn in the year of capture. This hypothesis was supported by the Vg values of an additional 19 tagged females recaptured in Newfoundland and mainland rivers and brackish water off mainland rivers in 1976.Significant correlations between stage of gonadal development and plasma Vg, stage of gonadal development and gonadosomatic index (GSI), stage of gonadal development and plasma E2, plasma Vg and plasma E2, GSI and plasma E2, and between plasma Vg and 11-keto values were found for the female fish. The gonadal development of female fish from Bonavista Bay ranged between oil globule stage and secondary yolk stage. All those females which had reached the primary yolk stage would almost certainly mature and may be considered spawners of the year; on this basis 91% of the females were spawners of the year. Based on the minimum plasma Vg values, at sea, for fish which subsequently returned to the rivers, there were 86% spawners of the year among female salmon taken in Bonavista Bay. Based on plasma Vg levels, spawners of the year ranged from essentially zero in Greenland (fish captured in Greenland during August–November are not spawners of the year, except for the very few that spawn in one Greenland river) to 100% for fish caught in several other fisheries.11-Ketotestosterone was higher in the male fish than in the female fish and there was a correlation between GSI and 11-keto for male fish.The plasma GtH content of fish taken in the sea was extremely low as measured by RIA.Key words: salmon, maturation, migration, radioimmunoassay, vitellogenin, estradiol, gonadotropin, 11-ketotestosterone, histology, gonadosomatic index

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Winter temperature and food quality affect age at maturity: an experimental test with Atlantic salmon (Salmo salar)

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f2012-108 ◽

2012 ◽

Vol 69 (11) ◽

pp. 1817-1826 ◽

Cited By ~ 13

Author(s):

Bror Jonsson ◽

Anders G. Finstad ◽

Nina Jonsson

Keyword(s):

Growth Rate ◽

Atlantic Salmon ◽

Direct Effect ◽

Salmo Salar ◽

Food Quality ◽

Condition Factor ◽

Sea Water ◽

Winter Temperature ◽

Age At Maturity ◽

Atlantic Salmon Salmo Salar

Field studies have revealed that many ectotherms mature younger and smaller in warmer environments although they grow faster. This has puzzled ecologists because the direct effect of factors that accelerate growth is expected to be larger, not smaller size. We tested this experimentally for Atlantic salmon (Salmo salar) at two winter temperatures and diets. Logistic regression revealed that the probability of maturation during the second year in sea water, relative to the probability of older maturation, increased with temperature and growth rate during the first winter. Also, large size and high condition factor 1 year prior to maturation stimulated maturation. In females, a high lipid diet increased the probability of maturation as one-sea-winter fish, and there were significant interactions between winter temperature and food quality and between body size and condition factor the first autumn in sea water. Thus, if the direct effect of temperature on growth rate is the main effect of warming, salmon are likely to attain maturity younger and smaller. Also, richer food decreased age at maturation in females. This finding has consequences for interpretations of climate change impacts on age at maturity in Atlantic salmon and may also hold for many other ectotherm species.

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Caligus elongatus (Copepoda: Caligoida) from Atlantic salmon (Salmo salar) cultured in marine waters of the Lower Bay of Fundy

Canadian Journal of Zoology ◽

10.1139/z89-150 ◽

1989 ◽

Vol 67 (4) ◽

pp. 1080-1082 ◽

Cited By ~ 15

Author(s):

W. E. Hogans ◽

Deborah J. Trudeau

Keyword(s):

Sex Ratio ◽

Atlantic Salmon ◽

Salmo Salar ◽

Gravid Female ◽

Market Size ◽

Bay Of Fundy ◽

Marine Waters ◽

Size Classes ◽

Atlantic Salmon Salmo Salar ◽

Passamaquoddy Bay

The occurrence of Caligus elongatus on Atlantic salmon (Salmo salar) cultured in marine waters in the Passamaquoddy Bay region of the lower Bay of Fundy is reported. Two size classes of cultured salmon (smolts and market size) were examined. Prevalence of C. elongatus was 54.5% on market fish and 54.7% on smolts. Intensities of infection for market fish and smolts were recorded as 2.41 and 2.58, respectively. Overall sex ratio of adult C. elongatus on infected salmon was 1:1.4 females to males; mean number of eggs per gravid female C. elongatus was 169.

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Activity, Respiration, and Excretion of Ammonia by Atlantic Salmon (Salmo salar) Smolt and Postsmolt

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f89-098 ◽

1989 ◽

Vol 46 (5) ◽

pp. 790-795 ◽

Cited By ~ 22

Author(s):

A. J. Wiggs ◽

E. B. Henderson ◽

R. L. Saunders ◽

M. N. Kutty

Keyword(s):

Oxygen Consumption ◽

Atlantic Salmon ◽

Spontaneous Activity ◽

Salmo Salar ◽

Condition Factor ◽

Ammonia Excretion ◽

Initial Increase ◽

Atlantic Salmon Salmo Salar ◽

Substantial Change ◽

Increased Activity

Spontaneous activity, oxygen consumption, and excretion of ammonia by juvenile Atlantic salmon (Salmo salar) were measured over 17 wk as the appearance of the fish changed from early smolt to smolt and then postsmolt. A substantial change in routine oxygen consumption from 66 to 148 mL∙kg−1∙h−1 was primarily correlated with the increase in activity. An initial increase in ammonia excretion from about 5 to about 14 mL∙kg−1∙h−1 was largely correlated with the decline in condition factor from 0.99 to 0.79 suggesting that increased metabolic needs caused by the increased activity were not being met by the amount of food ingested. This is supported by the secondary increase in condition factor (C.F. = 0.93) and decrease in ammonia excretion (to about 7 mg∙kg−1∙h−1) that occurred after the meal size was increased.

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

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f92-249 ◽

1992 ◽

Vol 49 (11) ◽

pp. 2273-2280 ◽

Cited By ~ 41

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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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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Distribution of Atlantic salmon (Salmo salar) postsmolts of different origins in the Bay of Fundy and Gulf of Maine and evaluation of factors affecting migration, growth, and survival

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f05-055 ◽

2005 ◽

Vol 62 (6) ◽

pp. 1363-1376 ◽

Cited By ~ 41

Author(s):

Gilles L Lacroix ◽

Derek Knox

Keyword(s):

Atlantic Salmon ◽

Salmo Salar ◽

Gulf Of Maine ◽

Fish Larvae ◽

Surface Current ◽

Clupea Harengus ◽

Bay Of Fundy ◽

Growth And Survival ◽

Atlantic Salmon Salmo Salar ◽

Salmon Lice

Atlantic salmon (Salmo salar) postsmolts surveyed by surface trawling in the Bay of Fundy and Gulf of Maine during 20012003 were aggregated in several areas in the Bay of Fundy and dispersed over a broader area in the Gulf of Maine. Postsmolt distribution reflected the major surface-current vectors and was independent of origin (wild vs. hatchery, inner vs. outer Bay of Fundy). Migration proceeded without disruption, and marked wild postsmolts from both the inner and outer Bay of Fundy were recaptured in the outer Bay of Fundy and the Gulf of Maine, where their distribution overlapped the commercial fishery for Atlantic herring (Clupea harengus). Marked postsmolts of wild origin were recaptured more frequently than those of hatchery origin but the overall density was low, and no schools of postsmolts were encountered that could offer protection from predators. Temperature and salinity in postsmolt habitat were favourable for growth and survival. Postsmolts were in excellent condition and had no bacterial or viral pathogens or salmon lice (Lepeophtheirus salmonis). They were feeding on pelagic prey (amphipods, euphausiids, and fish larvae) and the period of accelerated marine growth had started, indicating that environmental conditions and food supply were not limiting growth and survival.

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Mating structure of an endangered population of wild Atlantic salmon (Salmo salar) as determined using sibship reconstruction and a novel method of sex inference

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f2012-065 ◽

2012 ◽

Vol 69 (8) ◽

pp. 1352-1361 ◽

Cited By ~ 10

Author(s):

Louise G. de Mestral ◽

Christophe M. Herbinger ◽

Patrick T. O’Reilly

Keyword(s):

Atlantic Salmon ◽

Salmo Salar ◽

Mature Male ◽

Bay Of Fundy ◽

Multilocus Genotype ◽

Group Level ◽

Atlantic Salmon Salmo Salar ◽

Genotype Information ◽

Novel Method ◽

Mature Male Parr

The recent development of molecular genetic markers and methods of inferring relatedness among individuals using multilocus genotype information has allowed new insight into mating systems in the wild. Capitalising on the recently discovered linkage between the microsatellite locus Ssa202 and the sex-determining region of the Atlantic salmon Y chromosome, we developed a novel method to infer the sex of unsampled, wild-spawning parents of some of the few remaining wild, inner Bay of Fundy Atlantic salmon ( Salmo salar ). We inferred that most of the unsampled, reconstructed parents at the half-sib group level were likely polygamous females, while the parents at the full-sib group level (nested within half-sib groups) were likely monogamous males. Given the very low numbers of anadromous salmon returning to inner Bay of Fundy rivers to spawn, the putative male parents were likely mature male parr rather than anadromous males. This suggests that salmonid populations experiencing extreme declines may be composed of a high proportion of related individuals from relatively few sib groups and that mature male parr may provide an important genetic and demographic buffer to population decline.

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