The Ministry for Primary Industries says it wants people to question the cost of high-value fish at restaurants if the menu price seems too good to be true.
Staff seized four vehicles and a small boat yesterday as the ministry lifted the lid on a black-market fishing network in Christchurch and North Canterbury.
Six people have been interviewed, with a further 20 expected to be talked to. Charges are expected to be laid.
Southern compliance manager John Slaughter said an investigation into black-market trading in paua and rock lobster involved the use of an undercover officer.
Mr Slaughter said the demand for black-market fish was disturbing.
He said if the price of fish appeared too good to be true, it probably was.