Here's what the regs say:

Fillets are required to be kept whole until an angler reaches their permanent residence, or until the fish are prepared for immediate consumption. Frozen fish are required to be transported in such a way that the fillets can be easily identified and counted. This does not apply to anglers with a receipt from a fish cleaning house or charter captain which states the date, number, and type of fish possessed. Fish must be transported whole or as a complete fillet while returning from the Lake Erie islands on a commercial ferry boat.