Biomedical implications for managing the Limulus polyphemus harvest along the Northeast Coast of the United States

Abstract

North American horseshoe crabs (Limulus polyphemus) have been continuously harvested in Massachusetts for the production of Limulus amebocyte lysate (LAL); since the mid 1970s as bait for American eel (Anguilla rostrata); and since the mid 1990s as bait for whelk (Busycon ssp.). Harvest regulations were promulgated by the Atlantic States Marine Fisheries Commission (ASMFC) in 1998 over concern for the observed decline of the Red Knot (Calidris canutus), a correlation between its feeding behavior (horseshoe crab eggs during the spring migration), and a decline in spawning horseshoe crabs likely due to harvesting for bait. Generally, horseshoe crab harvest for the production of LAL (biomedical use) is exempted from harvest regulations, since the animals bled for LAL production are returned alive to the ocean, and mortality is considered low. However, evidence is accumulating that mortality of bled horseshoe crabs is higher than originally thought (29 % vs 15 %); that females may have an impaired ability to spawn following bleeding and release; and that bled crabs become disoriented and debilitated form various lengths of time following capture, handling, bleeding, and release. This paper reviews the latest evidence for mortality and impairment of horseshoe crabs bled for biomedical use, especially in Massachusetts where horseshoe crab populations in small bays and inlets are particularly vulnerable, and since State regulations allow for using bled crabs as bait rather than returning to the site of capture. A novel management plan is proposed that can satisfy all affected parties as well as insure a continued supply of horseshoe crabs for the vitally important production of LAL. This plan may also serve as a model for other areas of the Atlantic coast where biomedical harvest occurs.