No difference in survival, growth and morphology between offspring of wild-born, hatchery and hybrid brown trout (Salmo trutta)

– 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 × hatchery male and wild‐born male × 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.