Feeding of wild and hatchery reared Atlantic salmon (Salmo salar L.) smolts during downstream migration

Abstract

In general, hatchery salmonid smolts experience higher mortality during migration than wild smolts, which is suggested to be due to domestication effects and that hatchery fish lack experience of the natural environment. However, possible differences in feeding during smolt migration between hatchery and wild smolts have rarely been addressed. We compared the number of feeding smolts and stomach fullness among wild Atlantic salmon smolts, hatchery-reared smolts released as 1-year-old parr, and hatcheryreared smolts released as 2-year-old smolts during their descent to sea in River Tornionjoki. In addition, estimations of prey selection among the smolt groups were conducted. A high proportion of wild smolts and smolts stocked as parr actively fed during the smolt migration. A lower proportion of smolts stocked as smolts was feeding and their stomach fullness were much reduced in comparison with the two other groups. The study also indicated that the feeding of migrating smolts is selective rather than opportunistic.In conclusion, this study suggests that stocked 2-yearold smolts may enter sea with an inferior foraging behaviour and it is a possibility that this may contribute to the observed low post-smolt survival in the Baltic Sea.

Differences in Lateral Line Morphology between Hatchery- and Wild-Origin Steelhead

“…Fish were obtained from genetically similar stocks of steelhead native to Washington State's Olympic Peninsula (Queets-Quinault WRIA, [29]). Significantly fewer SN were observed in hatchery-reared juveniles, suggestive of functional deficits in lateral line-mediated behaviors, and perhaps reflective of behavioral deficits reported previously [14], [30]. In additional analyses, otolith composition and brain weight were also found to be different in hatchery-reared juveniles as compared to their wild-origin counterparts, in agreement with previous work in other Oncorhynchus species [12], [14], [31].…”

“…These data suggest that hatchery-reared juveniles with reduced SN might be less sensitive than wild fish to biologically relevant biotic and abiotic stimuli (e.g., in-stream flow obstacles, prey, or predators) during the period of outmigration and perhaps beyond. While this possibility seems particularly tenable in light of recent studies demonstrating reduced predator avoidance and altered swimming and migration behaviors in hatchery-reared Oncorhynchus [14] and reduced foraging success in hatchery-reared S. salar [30], carefully designed behavioral and physiological assays are required to validate such conjecture.…”

Effects of tagging on migration behaviour, survival and growth of hatchery‐reared Atlantic salmon smolts

“…; Hyvärinen & Rodewald ), although it suggests that they may enter sea with an inferior foraging behaviour, and this may contribute to lower post‐smolt survival (Larsson et al . ).…”

Are hybrids between Atlantic salmon and brown trout suitable long‐term hosts of Gyrodactylus salaris during winter?

“…Naïve hatchery‐reared hybrids can also suffer from starvation within the natural river environment they are released into (Larsson et al . ; Saikkonen, Kekalainen & Piironen ), although hatchery fish have high fat deposits and can thus survive long periods without feeding (Davidsen et al . ).…”