How are horseshoe crabs used as bait in commercial fishing?

The commercial fishing industry utilizes the American horseshoe crab (Limulus polyphemus) as bait to capture whelks and American eels (Anguilla rostrata). These eels, in turn, are frequently used as bait by fishers to catch striped bass (Morone saxatilis).12

This practice is a significant contributor to the mortality of adult horseshoe crabs. Because this industry removes large numbers of adults from the population, fewer individuals return to spawning beaches to lay and fertilize eggs. This decline in spawning activity is considered a major factor in the population crashes of shorebirds, such as the American red knot, which rely on horseshoe crab eggs as a critical food source during their migration.21