Customs officials said on Friday that they had seized more than 3,000 kilogrammes of Australian lobster that they believed was to be smuggled to the mainland by sea.
Thirteen people were arrested, some on suspicion of making inadequate import declarations.
Rita Li from customs' syndicate crimes investigation bureau said authorities on both sides of the border took action after Hong Kong saw a surge in Australian lobster imports.
"Hong Kong customs have set up a dedicated team to step up intelligence exchanges with mainland law enforcement agencies and conduct in-depth intelligence analysis," she said.
Li linked the alleged smuggling to a move by the mainland a year ago to impose strict restrictions on imports of Australian lobster. Last year, the mainland imposed an unofficial ban on Australian lobsters, after the Australian government pushed for an international investigation into the origins of Covid.
Li added that the seafood had not been handled correctly, with the suspected smugglers failing to chill it during transport.
As part of the operation, mainland officials arrested seven people and seized more than 2,000 kilogrammes of lobster, Customs said.