to fish

[Maria A]

What is correct?

he's fishing for a fish.

or

he's fishing a fish.

[Mister Micawber]

.
Actually, just 'He's fishing'. We assume that it is for a fish.
.

[riverkid]

Mr Micawber is correct in that there's no need to mention 'fish' unless it's a particular kind of fish.

He's fishing for grayling/brook trout/squid/sea bream.

[river]

"Fishing for" a particular kind of fish as Riverkid said or something other than fish, such as "a compliment," or "information," or "change."

[Maria A]

Thanks for your help!!!