29 C.F.R. § 784.133

Processing connotes a change from the natural state of the marine product and first processing would constitute the first operation or series of continuous operations that effectuate this change. It appears that the first processing operations ordinarily performed on the fishing vessels at sea consist for the most part of eviscerating, removal of the gills, beheading certain fish that have large heads, and the removal of the scallop from its shell. Icing or freezing operations, which ordinarily immediately follow these operations, would also constitute an integral part of the first processing operations, as would such activities as filleting, cutting, scaling, or salting when performed as part of a continuous series of operations. Employment aboard the fishing vessel in freezing operations thus performed is within the exemption if the first processing of which it is a part otherwise meets the conditions of section 13(a)(5), notwithstanding the transfer by the 1961 amendments of “freezing”, as such, from this exemption to the exemption from overtime only provided by section 13(b)(4). Such preliminary operations as cleaning, washing, and grading of the marine products, though not exempt as first processing since they effect no change, would be exempt as part of first processing when done in preparation for the first processing operation described above including freezing. The same would be true with respect to the removal of the waste products resulting from the above described operations on board the fishing vessel.