Farmed Atlantic salmon Salmo salar L. parr may reduce early survival of wild fish

Abstract

The study examined the density-mediated effects on growth, survival and dispersal of wild and farmed Atlantic salmon Salmo salar offspring in the period immediately following emergence, using a substitutive design. In small confined stream channels, wild parr coexisting with farmed parr had a significantly poorer survival, than wild parr alone. Density did not affect this relationship. In larger unconfined stream channels, wild parr coexisting with farmed parr entered a downstream trap in higher numbers than wild parr in allopatry. The results suggests that during the earliest life stages, farmed S. salar can outcompete wild S. salar, resulting in a reduced survival of wild S. salar.

Can variation in standard metabolic rate explain context‐dependent performance of farmed Atlantic salmon offspring?

“…ity and competition treatments among our wild families. This finding is consistent with that ofSundt-Hansen et al (2015) where fry with two farmed parents even had higher survival than fry with wild parents under conditions similar to those in our experiment. This was true both when they were alone (allopatry) and in competition (sympatry) with their wild half-siblings under near-natural conditions.…”

“…Combined with results from earlier studies Sundt-Hansen et al, 2015), this demonstrates that genetic introgression of farmed salmon may represent a direct cost to wild populations by imposing increased mortality on genetically wild individuals at the critical early life stage. That is, irrespective of maternal effects due to, for example, egg size differences between farmed and wild mothers.…”

“…The stream channels were 4.5 m long, 24 cm wide, had a water level of 10-15 cm, and gravel substratum suitable for salmon juveniles (see e.g., Sundt-Hansen et al, 2015). The stream channels were 4.5 m long, 24 cm wide, had a water level of 10-15 cm, and gravel substratum suitable for salmon juveniles (see e.g., Sundt-Hansen et al, 2015).…”

“…In doing so, we also test whether the previously found negative impact on early survival of wild offspring inflicted by the presence of pure farmed salmon offspring (Sundt-Hansen, Huisman, Skoglund, & Hindar, 2015) extends to hybrids. In doing so, we also test whether the previously found negative impact on early survival of wild offspring inflicted by the presence of pure farmed salmon offspring (Sundt-Hansen, Huisman, Skoglund, & Hindar, 2015) extends to hybrids.…”

Plasticity in growth of farmed and wild Atlantic salmon: is the increased growth rate of farmed salmon caused by evolutionary adaptations to the commercial diet?

“…Within the natural diet treatment wild fish had the lowest average survival. Sundt-Hansen et al [64] found that offspring of farmed salmon displaced and out-competed offspring of wild salmon in a short-term experiment conducted in a simulated stream environment, resulting in a lower survival of wild conspecifics. In the present study, food was presented in excess in each treatment to reduce or eliminate resource competition.…”