The relationship between stream or river discharge and thyroid hormone levels in wild adult Atlantic salmon (Salmo salar L.)

1992 ◽  
Vol 70 (1) ◽  
pp. 140-144 ◽  
Author(s):  
Alan F. Youngson ◽  
John H. Webb
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Discharge Rate ◽  
Water Velocity ◽  
Hormone Levels ◽  
Stream Discharge ◽  
Atlantic Salmon Salmo Salar ◽  
Discharge Rates ◽  
Probable Consequence ◽  
The Relationship

Thyroxine and tri-iodothyronine levels were determined in groups of adult Atlantic salmon (Salmo salar L.) of both sexes at river entry in summer or as they entered a spawning tributary in late autumn. Hormone levels were considered in relation to river or stream discharge rate at capture. For tri-iodothyronine, there was a quadratic or linear relationship with discharge rate for each sex at both sites. For thyroxine, there was a quadratic relationship with discharge rate at tributary entry but no relationship with discharge rate at river entry. It is argued that raised hormone levels at higher discharge rates are a probable consequence of increased motor activity associated with greater water velocity. The quadratic nature of most of the models is attributed to physiological or behavioural limitation of the response.

Relationship of upstream migrating adult Atlantic salmon (Salmo salar) and stream discharge within Catamaran Brook, New Brunswick

2007 ◽  
Vol 64 (3) ◽  
pp. 563-573 ◽  
Author(s):  
Sean C Mitchell ◽  
Richard A Cunjak
Keyword(s):  
Body Size ◽  
Atlantic Salmon ◽  
New Brunswick ◽  
Salmo Salar ◽  
Predictive Ability ◽  
River System ◽  
Low Flow ◽  
Stream Discharge ◽  
Atlantic Salmon Salmo Salar ◽  
Adult Abundance

Stream discharge has long been associated with abundance of returning adult spawning salmonids to streams and may also affect body size distribution of adult salmon as low flows interfere with returns of larger-bodied fish. We examined these relationships of abundance and body size within Catamaran Brook, a third-order tributary to the Miramichi River system of New Brunswick, Canada, to investigate the causes of a declining trend in annual returns of Atlantic salmon (Salmo salar) to this stream. Regression models of adult abundance, proportion of the run as grilse, and body size of returning adults as functions of maximum daily stream discharge during the period of upstream spawner migration were constructed. Adult abundance shows a logarithmic relationship with stream discharge and provides good predictive ability, while appearing to not be significantly related to adult abundance in the larger Miramichi system. The proportion as grilse in the run and female body size are also logarithmically related to stream discharge, with low flow years being very influential in the regressions. These relationships of Atlantic salmon population abundance and body size characteristics have implications with respect to stock integrity and production of the following generation.

Osmoregulation, feed intake, growth and growth hormone levels in 0+ Atlantic salmon (Salmo salar L.) transferred to seawater at different stages of smolt development

Aquaculture ◽  
2003 ◽  
Vol 222 (1-4) ◽  
pp. 167-187 ◽  
Author(s):  
Arne M. Arnesen ◽  
Hilde Toften ◽  
Thorleifur Agustsson ◽  
Sigurd O. Stefansson ◽  
Sigurd O. Handeland ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Feed Intake ◽  
Hormone Levels ◽  
Atlantic Salmon Salmo Salar

Changes in the Selection of Microhabitat by Juvenile Atlantic Salmon (Salmo salar) at the Summer–Autumn Transition in a Small River

1984 ◽  
Vol 41 (3) ◽  
pp. 469-475 ◽  
Author(s):  
D. M. Rimmer ◽  
U. Paim ◽  
R. L. Saunders
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Water Depth ◽  
Water Velocity ◽  
Bottom Surface ◽  
Age Classes ◽  
Atlantic Salmon Salmo Salar ◽  
Juvenile Atlantic Salmon ◽  
Wide Range ◽  
Maximum Water

Over three summers we used direct underwater observation to examine the summer to autumn differences in seven microhabitat properties of three age-classes of juvenile Atlantic salmon (Salmo salar) in the Little Sevogle River of northeastern New Brunswick. Salmon of all three age-classes occupied a wide range of water depths during summer, but were concentrated mainly in depths of 24–36 cm. In autumn, they occurred in this range almost exclusively. The streambed stones most closely associated with the individual positions of all ages were always <20 cm in summer and mostly (84–92%) <10 cm in diameter. In autumn, all ages were associated with home stones up to 40 cm in diameter, with 65–83% of the stones exceeding 20 cm; the size of home stones selected increased with fish age in autumn. There was no apparent relationship between the water depth and home stone size distributions occupied by all age-classes and available in the stream during either summer or autumn. Summer focal water velocity (velocity at the fish's snout) was predominantly 10–30 cm∙s−1 for 0+, 10–40 cm∙s−1 for 1+, and 30–50 cm∙s−1 for 2+ salmon, but during autumn it was almost always <10 cm∙s−1 for all ages. The bottom and surface water velocities as well as the maximum water velocity within 1 m of fish stations increased with fish age during summer and autumn. At the summer–autumn transition, 0+ salmon selected higher bottom, surface, and maximum water velocities, 2+ salmon selected lower velocities, but selection by 1+ salmon remained unchanged. We view substrate size followed by water depth as the primary properties influencing stream suitability for juvenile Atlantic salmon in autumn.

Growth, Parr–Smolt Transformation, and Changes in Growth Hormone of Atlantic Salmon (Salmo salar) Reared under Different Photoperiods

1991 ◽  
Vol 48 (11) ◽  
pp. 2100-2108 ◽  
Author(s):  
Sigurd O. Stefansson ◽  
Björn Th. Bjömsson ◽  
Tom Hansen ◽  
Carl Haux ◽  
G. Lasse Taranger ◽  
...  
Keyword(s):  
Growth Hormone ◽  
Growth Rate ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Continuous Light ◽  
Plasma Growth Hormone ◽  
Hormone Levels ◽  
Light Regimes ◽  
Atlantic Salmon Salmo Salar ◽  
Natural Photoperiod

Potential 1+ smolts of Atlantic salmon (Salmo salar) were reared under three light regimes: simulated natural photoperiod (LDN), continuous light (LD24:0), or a combination of continuous, low-intensity background light and a superimposed simulated natural photoperiod (dual photoperiod, LDD). Growth rate in freshwater was enhanced by LD24:0 and LDD, and changes associated with smoking (increased salinity tolerance, reduced condition coefficient) were advanced under LD24:0. Plasma growth hormone levels were initially high on LD24:0 and LDD whereas on LDN, plasma growth hormone levels increased gradually from February through April. Overall GH levels were negatively correlated with condition coefficient during the final stages of smoking. After 16 mo in seawater, there were no significant size differences among the groups. The incidence of sexual maturation as postsmolts was higher in the LD24:0 and LDD groups whereas the incidence of grilsing was higher in LDN. Results demonstrate the significant influence of photoperiod on growth and smoking in Atlantic salmon. An abrupt increase to continuous light in winter may be sufficient to advance important aspects of the parr–smolt transformation. Dual photoperiod may be a way to combine the increased growth rate observed under continuous light and the normal parr–smolt transformation associated with natural photoperiod.

Transferability of habitat suitability criteria of juvenile Atlantic salmon (Salmo salar)

2002 ◽  
Vol 59 (2) ◽  
pp. 218-228 ◽  
Author(s):  
Aki Mäki-Petäys ◽  
Ari Huusko ◽  
Jaakko Erkinaro ◽  
Timo Muotka
Keyword(s):  
Atlantic Salmon ◽  
Salmo Salar ◽  
Habitat Suitability ◽  
Fish Habitat ◽  
Regional Scale ◽  
Water Velocity ◽  
Atlantic Salmon Salmo Salar ◽  
Juvenile Atlantic Salmon ◽  
Depth Water ◽  
Universal Scale

We constructed generalized habitat criteria for juvenile Atlantic salmon (Salmo salar) based on four river-specific suitability indices for depth, water velocity, and substrate to assess whether habitat criteria for juvenile Atlantic salmon are transferable across rivers. We first tested whether salmon are more likely to occupy higher-quality habitats than generally available in a stream reach based on these composite criteria. We then repeated the same procedure using the river-specific criteria of this study and the generalized habitat suitability criteria of Heggenes. As expected, the river-specific criteria were generally the most effective ones in predicting fish habitat use. However, both of the two generalized criteria also transferred fairly well to the test sites. Viewed across salmon size-classes (<9 cm and >9 cm), the river-specific criteria passed the test in ten of eleven cases (91%), and the two generalized criteria passed in nine (82%) of eleven. Thus, it appears that with respect to summertime habitat criteria for juvenile Atlantic salmon, criteria transference is conceivable at least on a regional scale, and perhaps even on a more "universal" scale.

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