In every city there is still a place even the most gourmet may have not yet discovered. Istridye Balik may be in fact be one of those places, which unless an insider had taken me to, I would not have discovered...
Fındıklı is in the vicinity of Karaköy, where a lot of the Banks and also Istanbul Modern Museum are located... As such, it should not be a major surprise that one you go in at lunch time, there are quite a good number of black suit and ties people (bankers) are inside.
The place is very small and is not luxurious at all; but the food is good. It serves only fresh fish. No alcohol, no bosphorus view despite the fact that it is near Karaköy (part of European coastline); but the taste of fish is just very good.