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- Dahl, J., et al.
(författare)
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No difference in survival, growth and morphology between offspring of wild-born, hatchery and hybrid brown trout (Salmo trutta)
- 2006
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Ingår i: Ecology of Freshwater Fish. - : Wiley. - 0906-6691 .- 1600-0633. ; 15:4, s. 388-397
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Tidskriftsartikel (refereegranskat)abstract
- We studied survival, growth and morphological characters in the offspring of native hatchery and wild-born anadromous brown trout (Salmo trutta) and their hybrids (wild-born female x hatchery male and wild-born male x hatchery female) in a 1-year field experiment. We also conducted laboratory studies where we examined social interactions between the offspring of the same hatchery and wild-born trout. All offspring were raised in a hatchery and nose tagged before being released into the stream. In total, 1125 individuals were released into the stream (1999) and a total of 614 individuals were recovered (2000). We found no differences in growth and survival between the offspring of hatchery, wild-born and hybrid trout. Morphology was also similar among groups, where only 38% females and 36% males were classified into the right category, which were only 12% better than random classification. In the laboratory experiment, we compared only the offspring of hatchery and wild-born trout with respect to growth, dominance, aggressiveness, feeding and activity. We found small differences between the offspring of hatchery and wild-born fish with respect to growth but this effect was not found in the field experiment. Our result suggests that the offspring of hatchery trout and hybrids between hatchery and wild-born trout performed equally well to the offspring of wild-born trout.
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- Petersson, E, et al.
(författare)
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Male-male competition and female choice in brown trout
- 1999
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Ingår i: Animal Behaviour. - : Elsevier. - 0003-3472 .- 1095-8282. ; 57, s. 777-783
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Tidskriftsartikel (refereegranskat)abstract
- In some salmonid species, the females have been assumed to choose their mates on the size of the male's adipose fin. This hypothesis was tested in a stream water aquarium, in which 19 brown trout, Salmo trutta, females were allowed to choose between two males of the same body size but with different adipose fin sizes. The two males were separated from each other in cages. After the female had started to prepare her nest close to one of them, the males were released and allowed to fight each other for the opportunity to spawn. Out of 19 females, 14 prepared a nest closest to the male with the larger adipose fin. However, only six of the 14 females spawned with this male. Males that spawned were more dominant (i.e. were more likely to win fights). When the female spawned with the male she chose, he was less aggressive towards her than when she spawned with the other male. There were no significant differences in the plasma levels of testosterone (T) and 11-ketotestosterone (11-KT) between the chosen males and those not chosen. However, the dominant males had significantly higher plasma levels of T and 11-KT both before and after the experiment. The results support the view that female brown trout exhibit mate choice, but their choice is overruled by male-male competition.
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- Sundström, L. Fredrik, 1972, et al.
(författare)
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Heart rate responses to predation risk in Salmo trutta are affected by the rearing environment
- 2005
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Ingår i: Journal of Fish Biology. - : Wiley. - 1095-8649 .- 0022-1112. ; 67:5, s. 1280-1286
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Tidskriftsartikel (refereegranskat)abstract
- Both wild‐ and hatchery‐reared brown trout Salmotrutta, 18 months of age and of the same genetic origin, responded with increased heart rates (tachycardia) to a simulated predator attack on 2 consecutive days. Brown trout reared in the hatchery showed a more rapidly induced tachycardia compared with wild‐reared fish at day 1, but not day 2. During an undisturbed period several hours after attacks, hatchery‐reared brown trout maintained higher heart rates compared to wild‐reared fish on both days. Behavioural responses to the attack were very low for all fish, although hatchery‐reared fish tended to be more active than wild fish after the attack day 2. The observed differences may have had a genetic background caused by different selection regimes in the hatchery‐ and wild‐rearing environments, or could have been due to different phenotypic responses in the two environments.
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