Graham,
You've probably already seen the Ythan terrors of 'fable', when I was a regular on the Ythan estuary I used bastardised versions of those to some effect.
To be fair, I got a smidgen irritated as I continually caught tiddlers (wee finnock) and there's nothing more irritating/upsetting than catching loads of them that had pretty much swallowed my creations down their throats.
The problem, I surmised, was depth and size of the pattern. I was fishing far too shallow using an intermediate with a fast sinking polyleader and too small with 3-4" terror type flies.
I rectified that but too little too late, I gave up my membership of the Newburgh AC as it was just too far and on occasion too distressing to fish. That said, I managed a few nice fish (to about 6lb) on essentially a Di7 shooting head and the same terror type patterns.
Today my suggestion would be that if you're going to get the better fish on fly (hint: on the estuary head for the mussel beds at the end of Inch Road
) then look at something like a Rio Outbound type 6 matched to a suitable polyleader a short leader and a meaningful streamer/polar fibre creation which must be at
least as big as the Sutherland Special I spy on your spinning rig
Think of fishing the flies the same way as you would a Sutherland Special or a Tasmanian Devil and you'll be on the right path
As to the contents of the stomach you're looking at two common sprats and a very fine collection of shrimp.
I'd concentrate on sprat size patterns
H