9 C.F.R. § 539.2 – Physical, chemical, or biological contaminants.

(a) Fish and fish products that are contaminated with physical matter are subject to official retention and condemnation.
(b) Antibiotic or other drug residues in fish tissues must be within applicable tolerances in 21 CFR part 556 or within an applicable import tolerance established under 21 U.S.C. 360b(a)(6).
(c) Pesticide residues in fish tissues must be within applicable tolerances in 40 CFR part 180.
(d) Fish or fish products containing violative concentrations of drugs or other chemicals are subject to condemnation.