Biological and growth data of wild and hatchery-reared sea trout (Salmo trutta L.) individuals

Each year, millions of hatchery-reared sea-run brown trout Salmo trutta L.
(the sea trout) juveniles are released into the natural environment in the
Atlantic region. The aim of this work was to investigate the growth
responses of sea trout to changing temperature conditions and to compare
the growth plasticity between wild and hatchery-reared fish. Scales were
collected from sea trout in a selected river flowing into the southern
Baltic Sea. We analyzed the scale increment widths as a proxy of somatic
growth and investigated the interannual variabilities and differences in
growth between fish groups (wild and hatchery-reared). We used
mixed-effects Bayesian modeling and ascribed the variances in growth to
different sources. Furthermore, we developed indices of interannual
(2003–2015) growth variation in the marine and freshwater phases of the
life cycle of the fish and analyzed the relationships between trout growth
and temperature. Temperature positively affects fish growth, regardless of
the origin of the fish. We observed stronger relationships between fish
growth and temperature conditions in the marine phase than in the
freshwater phase. Additionally, wild sea trout are characterized by
stronger responses to temperature variability and higher phenotypic
plasticity of growth than those of the hatchery-reared individuals.
Therefore, wild sea trout might be better suited to changing environmental
conditions than hatchery-reared sea trout. This knowledge identifies
possible threats in management actions for sea trout with an emphasis on
ongoing climate change.