Differential lifetime success and performance of native and non‐native Atlantic salmon examined under communal natural conditions

Abstract

The lifetime success and performance characteristics of communally reared offspring of wild native Burrishoole (native), ranched native (ranched) and non-native (non-native) Atlantic salmon Salmo salar from the adjacent Owenmore River were compared. Non-native 0þ year parr showed a substantial downstream migration, which was not shown by native and ranched parr. This appears to have been an active migration rather than competitive displacement and may reflect an adaptation to environmental or physiographic conditions within the Owenmore River catchment where the main nursery habitat is downstream of the spawning area. There were no differences between native and ranched in smolt output or adult return. Both of these measures, however, were significantly lower for the non-native group. A greater proportion of the non-native Atlantic salmon was taken in the coastal drift nets compared to the return to the Burrishoole system, probably as a result of the greater size of the non-native fish. The overall lifetime success of the non-native group, from fertilized egg to returning adult, was some 35% of native and ranched. The ranched group showed a significantly greater male parr maturity, a greater proportion of 1þ year smolts, and differences in sex ratio and timing of freshwater entry of returning adults compared to native, which may have fitness implications under specific conditions. # 2004 The Fisheries Society of the British Isles

Divergent trends in anadromous salmonid populations in Norwegian and Scottish rivers

“…Hydropower development has resulted in habitat loss, and fish transfer and salmon farming have been implicated in the increased prevalence of the potentially harmful ectoparasites, Gyrodactylus salaris and Lepeophtheirus salmonis, with losses of fitness due to interbreeding of escaped farmed fishes with wild ones (McGinnity et al , 2004. Most of these impacts appeared after the late 1980s and, because of their strong local dimension, their effects will not be uniformly evident among rivers.…”

Reduced migratory performance of farmed Atlantic salmon post-smolts from a simulated escape during autumn

“…Genetic introgression resulting from escaped farmed fish spawning with wild salmon is of great concern because of genetic differences between wild and domesticated strains of salmon (Lura & Saegrov 1991, McGinnity et al 2004, Naylor et al 2005, Skaala et al 2005, Ferguson et al 2007). Farmed salmon kept in fish farms until just before spawning are relatively unsuccessful in natural environments, due to competitive and reproductive inferiority resulting from domestication (Fleming et al 1996).…”

Feeding preference of recaptured Atlantic salmon Salmo salar following simulated escape from fish pens during autumn

“…One of the more serious challenges is that farming has been correlated with declines in natural salmon populations (Ford & Myers 2008). Escapees will interfere with the genetic make-up of wild stocks if they manage to interbreed and may potentially contribute to the spread of diseases and parasites (Lura & Saegrov 1991, Heuch & Mo 2001, McGinnity et al 2004, Naylor et al 2005, Hindar et al 2006, Skaala et al 2006, Ferguson et al 2007, Fraser et al 2010). …”