How long has it been in the freezer?? I mounted a rainbow that was in the freezer for 8 years. It made the job a lot harder because of how bad it was freezer burnt. I tell my customers to wrap it carefully in a wet towel, not just damp. Carefully place fish wrapped in wet towel in plastic bag, Roll up to remove as much air as possible. A fish stored this way will not get damaged or freezer burnt.
it will be fine. Most times I keep them in my freezer for about a year before i work on them. I worked on 1 the other week that was in the customers freezer for 5 years, I just soak them in water to let everything rehydrate the best I can, then mount up like normal.