If I lived near the sea I would cope with predations of sea birds.
In this case they came inland, took fresh water fish and as they are bacteria laden they then destroyed the natural balance of a fresh water pond leaving virtually no living fish.
You seem to be upset about overfishing of...
Seagulls by the Sea - OK, that is where they should be.
Seagulls inland - definitely NOT OK.
They took several fish from our pond last summer and (according our vet) introduced a bacterial infection which then killed most of the rest.
Absolute vermin.