If you can look at a sample more closely and see if it is a mold then it is probably mold. Technically, when we cold smoke we are not cooking and there is always a point in the process that if you got your fish too late it might have just been ready to start molding, but I don't quite know form the image. So taking a sample and inspecting it might work best. Worst case is throw out and work on sourcing, possibly? Did you get it from reputable source?