The Herring is a fish that can be caught in the ocean at The Beach during Spring and Winter. It can also be found randomly at the Traveling Cart for 100-1,000g.
Herring can be caught regardless of season using Magic Bait.
Herring can be placed in a Fish Pond, where they will reproduce every day. The initial pond capacity is 3 fish, but the capacity can be increased to 10 by completing two quests. The only possible output is blue Herring Roe.