Put you to the sword Martin, pickled ormer guts or mullet. ????
Good fish, red mullet, grey mullet all much of a muchness mate... golden grey mullet is good.
I have found giltheads to be variable in flavour, some have a sort of cucumber background taste and some are pretty boring.
One thing I always do is bleed my fish, this means killing them with a knife in the gills or if on a boat bleeding them and immediately putting them on ice.
I never do long dives but if I did I would carry ice in an insulated float during this hot weather especially.
I would say that mackerel are probabily the most susceptibility to fast decomposing but pollock is another fish that deaerates very quickly.
On the boat we use a cut down freshwater keep net, put over the side on every drift, all fish that are to be kept are bleed and put in the net until the next drift when they then go on ice.
There can be a huge different to well kept and prepared fish, filleting a fish that has warmed up to summer air temp and not been bleed results in the flesh going soft and tainted with blood.
I have a friend from north England who comes over every year, he loves sea food but I have to feed him almost rotten fish otherwise he just complains it tastes of nothing.
He is a huge fan of pollock but I have to leave it three days in the fridge, Bass has to be four days in the fridge.. I am almost gagging at the smell of strong fish in my kitchen.
I guess that some folk have been brought up on stinky flavoured fish but I was not!