Final answer:
The US Department of Commerce is responsible for voluntary inspections and grading of fish and fish products through NOAA's Seafood Inspection Program. The FDA is also involved in regulating food safety.
Step-by-step explanation:
The agency that oversees voluntary inspections and grading of fish and fish products is the US Department of Commerce (USDC), specifically through the National Oceanic and Atmospheric Administration’s (NOAA) Seafood Inspection Program. The FDA also plays a role in the regulation and supervision of food safety, with a focus on protecting and promoting public health. It is important to note that various federal agencies have roles in regulatory actions and public safety, including the EPA for water and air quality, and the FDA for food safety, among others.