Pattern of gonad maturation in a highly stocked population of brown trout (Salmo trutta L., 1758) from Central Italy

This study deals with the gonadal development and breeding season of a brown trout population in the river Metauro (Central Italy), a typical Apennine river with a short course and a highly unpredictable water flow. The results obtained showed that most individuals spawn between November and January, with a peak in December. This trend is similar to that observed in populations from Central Europe, but differs considerably from other populations at similar latitudes, which show a spawning peak between February and March. As brown trout in the river Metauro are heavily stocked with farmed strains of Atlantic origin, it is likely that in this population the reproductive characteristics have changed according to the pattern of North European populations. On the other hand, the unusual presence of mature trout in June could be the result of stocking with farmed individuals whose reproductive characteristics have been modified by breeders.