This report describes the work and results of a computer program used to predict the propagation of air gun noise to long distances in the water column. The acoustic propagation model used is the PlaneRay model.The sound levels found in the computer model was then used together with startle thresholds for cod. From this data we could find the distance where the sound level went below this threshold. Probably, this is the first time a state-of- the-art propagation model is combined with current and advanced knowledge of fish hearing sensitivity to actually produce estimates of the minimum distance between seismic shooting and fish populations to avoid irregular behavior.