How to catch Son of Crimsonfish | Stardew Valley

You need to have level 10 fishing skills with Advanced Iridium Rod and activate the Mr.Qi's Extended Family's quest at west of Ginger Island. You also need to purchase both Trap Bobber and Lead Bobber to facilitate fishing from Willy's Shop at Pelican Beach located at southeast of Stardew Valley. Now head to the path at the east of your farm and try to head southeast until you pass Elliot's house at Pelican Beach and cross the wooden bridge to another beach. Then head southeast of the beach until you reach the edge of the dock. Cast your rod into the ocean at maximum level and wait patiently for the fish to bite. Do take note that other fish may bite the bait as well and that Son of Crimsonfish is a very rare fish. You need to cast multiple times to catch it and unlike the other Legendary Fish where you can only catch them at particular season and in limited quantity, you can catch these fish multiple times at any season, as long you can have access to the Mr.Qi's Extended Family Quest that can be activated on Ginger Island.