A trout was a type of fish native to Earth, closely related to salmon.
Trout almondine was a dish available on Enterprise NX-01 in 2152. (ENT: "Singularity")
Trout were plentiful in Lake Shasta. In 2256, Ash Tyler talked with Michael Burnham about fishing for trout there and roasting them. (DIS: "Si Vis Pacem, Para Bellum")
A large trout in butter-lemon sauce was available at Sisko's Creole Kitchen in 2372. (DS9: "Homefront")
In the Fair Haven holoprogram in 2376, Seamus mentioned that he met his wife while he was traveling to Kilkee for some trout fishing. (VOY: "Fair Haven")
The fish which Jonathan Archer mentioned in his summary of The Song of the Wandering Aengus in "Rogue Planet" was in fact a trout.