The Echizen Fish Festival is Fukui Prefecture's largest fish-related event, and it's held at the time of year when the largest variety of fish can be caught. Various seafood items will be available for purchase at the festival, alongside experience-based activities like hopping on-board a fishing boat tour or taking part in fish catching (a participation fee of 1000 yen for certain activities applies, some require lottery entry).
Admission to the event itself is free of charge, but bring yen if you plan on making a purchase or taking part in any of the paid experiences.