can anyone give some info on this? For a strict kosher eater, halal meat is not acceptable, is it? What about fish from bosphorus? Is bosphorus considered salt water fish? I've heard differing opinions and short of tasting bosphorus water (ewwww) not sure how to confirm or deny this for a visitor arriving this month

My knowledge about the kosher subject isn't great (is virtually non existant actually) but I do know that for a strict kosher eater halal is not excepted. Have no idea about bosphorus fish, but a fish restaurant that serves fish and other non-kosher sea food (such as calamari) cannot be considered a kosher restaurant. I do know of two kosher restaurants in the city:
1. Carne Rest. Halaskargazi Cad. Uzay Apt. No 53 Harbiye Istanbul, +90-212-241 85 85
2. Levi, Tahmis Cad Sok Cavusbasi Han 23/10 Istanbul, +90 0212 512 11 96

Hope that helped a bit

Cartoon Hotel in Taksim offers a fixed menu kosher meal. In Laleli, the Merit Antique Hotel. On Buyukada there is Meshur Sultanahmet.
For meat, halal doesn't count. The butcher who sells it must be under rabbinical supervision.
Fish: no shellfish. Fish must have fins and scales - scales must be easily removeableand be thin, rounded and smooth-edged (cycloid), or similar to the shape of a comb (ctenoid). If they're really into keeping kosher, if the fish is skinned and filleted, they will want a small piece of the skin on the plate so that they can make sure it's ok.