A recent study published last year, monitored the migrations of Danish sea trout. Over the course of the study, research found that tagged sea trout spent an average of 96 days out at sea before returning to the river. Within that time, some fish traveled nearly 600 km away from the river mouth!
During their initial migration from the river, the fish stayed in warmer waters before travelling further out to sea in the summer months. In general, the fish migrated to areas where there was ideal water temperature for optimal growth.
For more information about their migration, check out the published work by scientists from the Technical University of Denmark.