Below is a walkthrough for the Fishing for Ingredients! support request in The Legend of Heroes: Trails from Zero. You can pick up this request from the terminal in Chapter 2.
Client: Long Lao Tavern & Inn – Shanshan
Salary: 1500 mira
Speak with Shanshan (waitress walking around) at the Long Lao Tavern & Inn on East Street. The fish she is looking for is an eel! You can fish for the eels in Crossbell at the dock near the lighthouse in the Harbor District.
When fishing, make sure to use the Novice Rod and an Earthworm! After you’ve gotten 5, return to Shanshan and speak with her to complete the quest. As a reward, you’ll receive Teara Balm x2 and the recipe for Fierce Tiger Fried Rice!