They are goldfish, shubunkins, orfe and one koi.
I dont have cats but they do visit the gardedn.
Since posting I have loosely laid another net over the other net and since then nothing has gone missing. So I think it might have been a bird that landed on the net at it was very taut across the pond and just managed to get its beak through to catch a fish but the holes in the net didnt allow for the whole fish to be pulled through.