Interstate fishing regulators are limiting the harvest of a primordial species of invertebrate to try to help rebuild its population and aid a threatened species of bird. Fishermen harvest horseshoe crabs on the East Coast for use as bait and in biomedical products. The animals are declining in some of their range, and they’re critically important as a food source for the red knot, a migratory shorebird listed as threatened under the Endangered Species Act. The regulatory Atlantic States Marine Fisheries Commission said it will allow no harvest of female horseshoe crabs that originate in the Delaware Bay in the 2024 fishing season.