Interactive effects of temperature and water exchange of depuration tanks on geosmin excretion by Atlantic salmon (Salmo salar)

The selection of illuminated or shaded areas by juvenile Atlantic salmon (Salmo salar) was examined in relation to temperature and photoperiod. Water temperature had a strong effect on the photoresponse of salmon. Salmon acclimated to 14 °C and a 16-h photophase in summer selected illuminated areas when tested at their acclimation conditions, but rapidly became strongly photonegative while temperature fell to 7 °C. When tested under acclimation conditions of 7 °C and a 16-h photophase during summer, salmon selected shade, but still became distinctly photopositive as temperature increased to 14 °C. Under acclimation conditions of 14 °C and an 8-h photophase during summer, salmon selected illuminated areas, becoming photonegative as temperature fell. Thus, acclimation to photoperiod alone did not exert a clear effect on the photoresponse of summer salmon. If acclimated to 7 °C and an 8-h photophase in winter, salmon selected shade under acclimation conditions and remained photonegative also after temperature increased. Anomalously, after acclimation to 7 °C and an 8-h photophase in summer, salmon were photopositive at 7 °C, but became photonegative and selected shade upon temperature increase, indicating an endogenous seasonal difference not only in their response to thermal stimuli, but also in their susceptibility to acclimation regimes.

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Effects of temperature and salinity on osmoregulation and growth of Atlantic salmon (Salmo salar L.) smolts in seawater

Aquaculture ◽

10.1016/s0044-8486(98)00356-1 ◽

1998 ◽

Vol 168 (1-4) ◽

pp. 289-302 ◽

Cited By ~ 68

Author(s):

S.O Handeland ◽

Å Berge ◽

B.Th Björnsson ◽

S.O Stefansson

Keyword(s):

Atlantic Salmon ◽

Salmo Salar ◽

Atlantic Salmon Salmo Salar ◽

Effects Of Temperature

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Interactive effects of substrate sand and silt contents, redd-scale hydraulic gradients, and interstitial velocities on egg-to-emergence survival of Atlantic salmon (Salmo salar)

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f04-236 ◽

2004 ◽

Vol 61 (12) ◽

pp. 2271-2277 ◽

Cited By ~ 47

Author(s):

Michel F Lapointe ◽

Normand E Bergeron ◽

F Bérubé ◽

M -A Pouliot ◽

P Johnston

Keyword(s):

Atlantic Salmon ◽

Salmo Salar ◽

Relative Sensitivity ◽

Interactive Effects ◽

Interstitial Flow ◽

Atlantic Salmon Salmo Salar ◽

Incubation Experiments ◽

Hydraulic Gradients ◽

Substrate Mixtures ◽

Positive Effect

We conducted laboratory incubation experiments with Atlantic salmon (Salmo salar) eggs to test a number of hypotheses concerning the relative sensitivity of the incubating eggs to variations in silt (diameter < 0.063 mm) in interaction with sand (0.63 mm < diameter < 2 mm) fractions in the incubating gravels, as well as to different strengths of local hydraulic gradients pushing flow across the egg pocket. Our results show that variations of only a few percent of silt content can strongly degrade survival to emergence. Higher silt loadings (>0.5%) are detrimental to survival for all substrate mixtures, except those that are very sparse in sands (<5%). For sand contents over 10%, an increment of 1% silt has over three times the effect on survival as a 1% increment in sand. Increasing hydraulic gradients had a positive effect on median survival, but the effect depended both on the details of the fines composition and on the gradient level. Our results suggest that silt loadings over 1.5% in redds cannot easily be mitigated by stronger gradients. Our data conclusively show that there is no single threshold interstitial flow velocity that insures survival to emergence. Even when maintaining a constant interstitial velocity, survival tended to reduce in higher fines-content substrate.

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