Typically I see Ibis catching small insects and other little ‘creepy’ things. Their bill is designed for digging in the mud, however fish is a good catch for them given the size.
It takes them longer than the other birds to eat a fish. All birds eat fish head first to avoid the sharp gills. An Ibis long bill doesn’t help this process very well.
A Gull can easily steal fish from Ibis, and it happens probably half the time.
Ibis will run with their prey as soon as possible. Probably hoping none noticed what he caught.