PORTLAND, Maine — A local firm pleaded guilty Friday in U.S. District Court to importing seafood from a Canadian firm not licensed under Canadian law to export sea urchins, according to the U.S. attorney’s office.

By pleading guilty, ISF Trading Co. of Portland admitted that on seven occasions between Dec. 31, 2010, and Feb. 1, 2011, ISF illegally imported a total of about 48,000 pounds of sea urchins, whose processed roe was worth at least $172,800, from TGK Fisheries of Grand Manan, Canada, through Calais.

ISF brought them across the Calais Port of Entry under the false label of another Canadian supplier, Matthews Seafood of New Brunswick, Canada, a press release issued Friday by the U.S. attorney’s office said. At times, Matthews was authorized to export them.

The scheme was discovered in February 2011, when ISF attempted to import 8,000 pounds of sea urchins, using an invoice in the name of Matthews, the press release said. A U.S. Customs and Border Protection officer became suspicious when he noticed that the totes containing the sea urchins did not have the labels required by law.

A sentencing date has not been set.

ISF faces up to five years of probation. Under its plea agreement with federal prosecutors, ISF faces up to $1.25 million in fines and forfeitures for the violations, the press release said.

The case was investigated by Customs and Border Protection and the National Oceanic and Atmospheric Administration.