Feeding Intensity, Growth Rates, and the Establishment of Life-History Patterns in Juvenile Atlantic Salmon Salmo salar

10.2307/4918 ◽  
1988 ◽  
Vol 57 (2) ◽  
pp. 463 ◽  
Author(s):  
N. B. Metcalfe ◽  
Felicity A. Huntingford ◽  
J. E. Thorpe
Keyword(s):  
Life History ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Growth Rates ◽  
Feeding Intensity ◽  
Atlantic Salmon Salmo Salar ◽  
Juvenile Atlantic Salmon ◽  
Life History Patterns

Effect of time of day, time of year, and life history strategy on time budgeting in juvenile Atlantic salmon, Salmo salar

1999 ◽  
Vol 56 (12) ◽  
pp. 2397-2403 ◽  
Author(s):  
Sveinn K Valdimarsson ◽  
Neil B Metcalfe
Keyword(s):  
Life History ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Life History Strategy ◽  
Time Of Day ◽  
Life History Strategies ◽  
Foraging Efficiency ◽  
Atlantic Salmon Salmo Salar ◽  
Juvenile Atlantic Salmon ◽  
Time Of Year

Traditionally, behavioural studies on juvenile Atlantic salmon, Salmo salar, have been conducted during the day in summer. It is known that Atlantic salmon become nocturnal in winter, but very little is known about their behaviour at that time. Therefore, observations in a seminatural stream were carried out during the day and night, from February to June, comparing diel and seasonal differences in behaviour between fish adopting alternative life history strategies. The results showed a general trend for more activity in spring than in winter, and the fish were found to be foraging at surprisingly low light levels. There were differences in relative feeding rate between the life history strategies; the early migrant fish foraged mostly during the day whereas the delayed migrant fish did more foraging at night. There is some evidence that the early migrant fish made fewer feeding attempts over the winter, which is surprising, since they grow faster over that period. This suggests differences in foraging efficiency, which could contribute to the separation into these two life history strategies.

Behavioural influences on life-history variation in juvenile Atlantic salmon, Salmo salar

1992 ◽  
Vol 33 (4) ◽  
pp. 331-340 ◽  
Author(s):  
John E. Thorpe ◽  
Neil B. Metcalfe ◽  
Felicity A. Huntingford
Keyword(s):  
Life History ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Life History Variation ◽  
Atlantic Salmon Salmo Salar ◽  
Juvenile Atlantic Salmon

Seasonal and Developmental Variation in the Lethality of Zinc to Juvenile Atlantic Salmon (Salmo salar)

1977 ◽  
Vol 34 (1) ◽  
pp. 139-141 ◽  
Author(s):  
V. Zitko ◽  
W. G. Carson
Keyword(s):  
Life History ◽  
Atlantic Salmon ◽  
Developmental Stage ◽  
Salmo Salar ◽  
Water Hardness ◽  
Developmental Variation ◽  
Atlantic Salmon Salmo Salar ◽  
Sensitive Stage ◽  
Juvenile Atlantic Salmon ◽  
Lethal Level

The incipient lethal level (ILL) of zinc to juvenile Atlantic salmon (Salmo salar) in fresh water at a water hardness of 14 mg/ℓ varies from 150 to 1000 μg/ℓ as a function of season and developmental stage of the fish. The ILL increases from 500 to 1000 μg/ℓ during the 1st yr and decreases to 150 μg/ℓ in the following spring. The more sensitive stage in the salmon's life history, evidenced by decrease of ILL coincides with and is probably related to initial stages of the parr–smolt transformation.

Differentiation in juvenile growth and bimodality patterns between northern and southern populations of Atlantic salmon (Salmo salar L.)

1994 ◽  
Vol 72 (9) ◽  
pp. 1603-1610 ◽  
Author(s):  
Alfredo G. Nicieza ◽  
Felipe G. Reyes-Gavilán ◽  
Florentino Braña
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Growth Rates ◽  
Individual Growth ◽  
Late Winter ◽  
Southern Population ◽  
Northern Spain ◽  
Atlantic Salmon Salmo Salar ◽  
Juvenile Atlantic Salmon ◽  
Modal Group

Juvenile Atlantic salmon, Salmo salar, from two contrasting populations that had been reared under identical conditions differed in freshwater growth rates and the development of bimodality in length–frequency distributions. Segregation by size started at least a month earlier in the northern (River Shin, northern Scotland) than in the southern population (River Narcea, northern Spain). Northern fish initially grew faster and entered the upper modal group at a larger size (about 100 mm) than did southern fish (about 90 mm). However, the percentage of fish in the upper modal group was greater for the southern population and they grew fastest over winter and during the spring leading up to smolting, and were larger at the smolt stage. By late winter, the individual growth rates of upper modal fish were inversely correlated with their body length in December. These results suggest the existence of genetic differences between populations in the expression of growth bimodality in juvenile Atlantic salmon. This may indicate that size and growth rate thresholds determining the developmental pathway associated with age at smolt metamorphosis may vary between populations as a function of both smolt size and expected growth opportunity during winter and spring.

Effects of Extended Daylength on Autumn Growth Dynamics of Juvenile Atlantic Salmon, Salmo salar

1990 ◽  
Vol 47 (4) ◽  
pp. 755-759 ◽  
Author(s):  
Mark W. Stewart ◽  
Richard L. Saunders ◽  
A. J. Wiggs
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Growth Rates ◽  
Size Range ◽  
Fork Length ◽  
Growth Dynamics ◽  
Atlantic Salmon Salmo Salar ◽  
Juvenile Atlantic Salmon ◽  
Light:Dark Cycle ◽  
Modal Group

The growth and growth dynamics of juvenile Atlantic salmon (Salmo salar) exposed from mid-August to mid-December to either a normal light:dark cycle (LDN) or a constant 16-h light:8-h dark (LD 16:8) photoperiod were compared. Exposure to the LD 16:8 resulted in 38.1% of the fish entering the upper modal group (UMG) of the length–frequency distribution, while only 15.4% entered the UMG under LDN. The length at which fish entered the UMG (critical fork length) did not differ between photoperiods. Fish in the small (5.8–6.7 cm) and middle (6.8–7.7 cm) size-ranges under LD 16:8 had greater growth rates than fish in the same size-ranges under LDN. Fish in the large (8.3–9.2 cm) size-range showed no significant variation in growth rates between photoperiods. At the end of the experiment, mean thyroxine (T4) levels were significantly (P < 0.05) lower in fish from the LD 16:8 photoperiod (1.69 ng/mL) in comparison with LDN fish (3.96 ng/mL). Triiodothyronine (T3) levels and the T3/T4 ratio were elevated under LD 16:8.

The influence of energetic requirements on the preferred temperature of overwintering juvenile Atlantic salmon (Salmo salar)

2001 ◽  
Vol 58 (4) ◽  
pp. 762-768 ◽  
Author(s):  
Ian J Morgan ◽  
Neil B Metcalfe
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Growth Rates ◽  
Energy Deficit ◽  
Life History Strategies ◽  
Preferred Temperature ◽  
Atlantic Salmon Salmo Salar ◽  
Juvenile Atlantic Salmon ◽  
Significant Difference ◽  
Final Preferred Temperature

We used a horizontal temperature gradient to investigate the effect of alternate life history strategies and nutritional state on the preferred temperature of overwintering juvenile Atlantic salmon (Salmo salar L.). Contrary to our prediction, there was no significant difference in final preferred temperature between juvenile Atlantic salmon that will migrate to sea the following spring (early migrants) and those that show reduced growth and delay migration for at least another year (delayed migrants). Both migrant groups preferentially selected relatively low temperatures (<10°C), likely owing to their low appetite and growth rates. Food deprivation resulted in a significant increase, rather than our predicted decrease, in the final preferred temperature of the juvenile Atlantic salmon of approximately 2°C. We suggest that this is due to the need for an increased foraging effort to offset the projected energy deficit later in the winter. The final preferred temperature of delayed migrants increased from winter to spring, as predicted, coincident with increases in natural food availability and endogenous seasonal increases in appetite and growth rates. We conclude that the preferred temperature of overwintering juvenile Atlantic salmon may be influenced by future energetic requirements rather than the current level of energy reserves.

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