Why can hagfishes be pests for commercial fisheries?

Hagfishes are considered pests to commercial fisheries because they frequently attack fish that have already been caught on lines or trapped in nets. These primitive vertebrates bore their way into the bodies of the captured fish and consume them from the inside, rendering the catch useless for commercial sale.1

While they are categorized as agnathans—a group of jawless fishes—their impact is generally considered minor compared to the more severe damage caused by parasitic lampreys in regions like the Great Lakes.2