High risk no gain-metabolic performance of hatchery reared Atlantic salmon smolts, effects of nest emergence time, hypoxia avoidance behaviour and size.
When animals are reared for conservational releases it is paramount to avoid reducing genetic and phenotypic variation over time. This requires an understanding of how diverging behavioural and physiological traits affect performance both in captivity and after release. In Atlantic salmon, emergence time from the spawning gravel has been linked to certain behavioural and physiological characteristics and to the concept of stress coping styles. Early emerging fry has for example been shown to be bolder and more aggressive and to have higher standard metabolic rates compared to late emerging fry. The first aim was therefore to examine if emergence latency affect the behavioural stress coping response also beyond the fry and parr stage. This was done using a hypoxia avoidance test, where an active behavioural avoidance response can be related to higher risk taking. No behavioural differences were found between the two emergence fractions either at the parr or pre-smolt stage, instead smaller individuals were more prone to express an "active" hypoxia avoidance response. Further, an individual expressing a "passive" response as parr were also more prone to express this behaviour at the pre-smolt stage. While there are some previous studies showing that early emerging individuals with a bolder personality may be favored within a hatchery setting it is not known to what extent these early differences persist to affect performance after release. The second aim was therefore to compare the physiological performance at the time of release as smolts using the two subgroups; 1) early emerging fish showing active hypoxia avoidance (Early+Bold) and 2) late emerging fish showing a passive hypoxia response (Late+Shy). The Early+Bold group showed a higher red blood cell swelling, suggesting a higher adrenergic output during stress, whereas there was no difference in post-stress plasma cortisol or physiological smolt status. While there was no difference in standard metabolic rate between the groups, the Early+Bold group exhibited a lower maximum metabolic rate and aerobic scope following strenuous swimming. In captivity this may have no clear negative effects, but in the wild, a more risk prone behavioural profile linked to a lower aerobic capacity to escape from e.g. a predator attack, could clearly be disadvantageous.
Department of Biological and Environmental Sciences, University of Gothenburg, PO Box: 463, 405 31 Gothenburg, Sweden. Electronic address: malin.rosengren@bioenv.gu.se.
Malin
M
Rosengren
Department of Neuroscience, Uppsala University, PO Box: 256, 751 05 Uppsala, Sweden. Electronic address: per-ove.thornqvist@neuro.uu.se.
Per-Ove
PO
Thörnqvist
Department of Biological and Environmental Sciences, University of Gothenburg, PO Box: 463, 405 31 Gothenburg, Sweden. Electronic address: jorgen.johnsson@bioenv.gu.se.
Jörgen I
JI
Johnsson
Department of Biological and Environmental Sciences, University of Gothenburg, PO Box: 463, 405 31 Gothenburg, Sweden. Electronic address: erik.sandblom@bioenv.gu.se.
Erik
E
Sandblom
Department of Neuroscience, Uppsala University, PO Box: 256, 751 05 Uppsala, Sweden. Electronic address: svante.winberg@neuro.uu.se.
Svante
S
Winberg
Department of Biological and Environmental Sciences, University of Gothenburg, PO Box: 463, 405 31 Gothenburg, Sweden. Electronic address: kristina.sundell@bioenv.gu.se.
Kristina
K
Sundell
D000223:Adaptation, Psychological / Q000502:physiology*; D025041:Animal Migration / Q000502:physiology*; D000818:Animals; D001362:Avoidance Learning / Q000502:physiology*; D001481:Basal Metabolism / Q000502:physiology*; D005880:Gills / Q000378:metabolism; D006854:Hydrocortisone / Q000097:blood; D000860:Hypoxia / Q000503:physiopathology / Q000523:psychology*; D010101:Oxygen Consumption; D020317:Salmo salar / Q000502:physiology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013550:Swimming
D000254:Sodium-Potassium-Exchanging ATPase; D006854:Hydrocortisone
Boldness; Fish; Oxygen consumption; Physiology; Smolt migration; Supplementary rearing