A stretch of beach in the US state of Virginia has been closed after dead fish accidentally caught by Cooke-owned Omega Protein's harvesting partner began washing ashore, according to The Virginian-Pilot.

On Monday, an Ocean Harvesters vessel fishing for menhaden encountered a "rare and unexpected" school of red drum in its net during harvesting.

In a statement about the incident, Omega Protein and Ocean Harvesters, whose fleet works on behalf of Omega Protein as part of a long-term supply contract, said a captain on the vessel noticed the group of red drum in a net while bringing menhaden aboard a vessel, and instructed the crew to open the net and release the fish.

Though many fish swam away, the captain acknowledged "many fish likely died during the incident," the companies said.

The companies added it has "no record of an incident of this kind occurring in the recent past."

Menhaden fishermen actively avoid red drum as they are considered bycatch in the fishery. The company immediately notified the Virginia Marine Resources Commission (VMRC) when the incident happened and takes "full responsibility."

It remains unclear how many fish were affected by the incident.

Omega Protein has dispatched crews to help clean the beach, and said it will monitor the beach for any other bycatch that washes ashore and clean it up.

The state expects the beach to re-open Thursday, according to The Virginian-Pilot.

"We acknowledge the impact and inconvenience Monday’s incident may have on the Eastern Shore community and will continue to focus our collective efforts on the situation until it is remedied," the company said.

Omega produces fish oil, protein-rich specialty fishmeal and other ingredients for livestock and aquaculture feed manufacturers.

Omega operates seven manufacturing facilities located in the United States, Canada and Europe. The company also operates more than 30 vessels that harvest menhaden in the Atlantic Ocean and Gulf of Mexico.

In addition to Omega Protein, the other major company operating in the Gulf menhaden fishery is Daybrook Fisheries, a wholly owned subsidiary of South Africa's Oceana Group.

Oceana Group CEO Imraan Soomra stepped down earlier this year after a whistleblower raised questions over how the group's 25 percent shareholding in Westbank Fishing, a subsidiary of Daybrook, was accounted for. No evidence of fraud was uncovered.