Mmm; fishes (ostracoderms) came ahead of the insects....
"The first insects were land bound, but about 400 million years ago in the Devonian period one lineage of insects evolved flight, the first animals to do so. The oldest definitive insect fossil, Rhyniognatha hirsti, is estimated to be 407 to 396 million years old."
"When did the first fish appear?
Ostracoderms (shell-skinned) are any of several groups of extinct, primitive, jawless fishes that were covered in an armour of bony plates. They appeared in the Cambrian, about 510 million years ago, and became extinct towards the end of the Devonian, about 377 million years ago."