The 2019 Seafood Expo North America in Boston featured an oyster-shucking contest, whole squid on ice and some surprising attendees: attorneys from the powerful political network of Charles Koch, a billionaire who has spent decades and millions fighting government regulation.

They weren’t there for the seafood samples. They were fishing for fishermen, seeking stories of boat captains upset by federal regulations that would soon require herring fishermen to pay for onboard government monitors.