From the DEC "General Regulations"
"Fish Cleaning Law
It is illegal on New York State waters to possess walleye, black bass, brook trout, lake trout or Atlantic salmon that have been cut, dismembered, filleted, skinned or otherwise altered so that the species and total length of such fish cannot be easily determined. However, these fish may be gilled or gutted. Other species of fish may be filleted provided that the skin is not removed from the fillets. This regulation allows more effective enforcement of harvest regulations on protected game fish."
Personally, I think this law is overkill and potentially causes way more aggravation than the good it accomplishes. The law is relatively new (10 yrs.?). I have proposed in writing getting rid of it. Nothing happens.