A good way to preserve a fish for mounting especially if you are a long way from home,backpacking,etc.is to put the fish in a pillow case with salt on the fish gently rubbed in the gill area,mouth and underneath the fins.The salt will help retain much of the natural color of the fish and absolutely prevent any faded streaks on the body.Also the salt process is extremely important as it will kill bacteria and help set the scales until the fish can be skinned,mounted or frozen.
another temporary method is to store in freezer.After measurements,color notations,an tagging,the fins and tail should be individually wrapped with damp paper towels or tissue and then carded with milk cartons and paper clips to prevent damage while in freezer.Wrap the fish in a 1 1/2" to 2" layer of wet newspaper,tape with 2" masking paper,and then put in at least one plastic garbage bag,two are better one over the head facing the tail, one over the tail facing the head.Use a twist tie to seal,then wrap the bag with 2" masking tape.Then write on the tape species,date etc.
A fish treated such as this can be stored a "long" time and will produce a much higher quality mount.Hope this helps.
Elkshed