WASHINGTON — Most of the justices seemed troubled by Supreme Court arguments on Wednesday about the prosecution of a Florida fisherman for throwing three undersize red grouper back into the Gulf of Mexico.

The fisherman, John L. Yates, was convicted of violating the Sarbanes-Oxley Act of 2002, a federal law aimed primarily at white-collar crime. The law imposes a maximum sentence of 20 years for the destruction of “any record, document or tangible object” in order to obstruct an investigation.

Mr. Yates’s primary argument was that fish are not the sort of tangible objects with which the law was concerned.

Chief Justice John G. Roberts Jr. seemed to agree. He asked what people would say “if you stopped them on the street and said, ‘Is a fish a record, document or tangible object?’ ”