29 CFR 784.104: The 1949 amendments.

In deleting employees employed in canning aquatic products from the section 13(a)(5) exemption and providing them with an exemption in like language from the overtime provisions only in section 13(b)(4), the conferees on the Fair Labor Standards Amendments of 1949 did not indicate any intention to change in any way the category of employees who would be exempt as “employed in the canning of” the aquatic products. As the Supreme Court has pointed out in a number of decisions, “When Congress amended the Act in 1949 it provided that pre-1949 rulings and interpretations by the Administrator should remain in effect unless inconsistent with the statute as amended 63 Stat. 920” (Mitchell v. Kentucky Finance Co., 359 U.S. 290). In connection with this exemption the conference report specifically indicates what operations are included in the canning process (see § 784.142). In a case decided before the 1961 amendments to the Act, this was held to “indicate that Congress intended that only those employees engaged in operations physically essential in the canning of fish, such as cutting the fish, placing it in cans, labelling and packing the cans for shipment are in the exempt category” (Mitchell v. Stinson, 217 F. 2d 210).