PORTLAND, Maine (AP) — Regulators say they need to get a firmer handle on how many horseshoe crabs die as part of their harvest for biomedical use.

The crabs are harvested for their blue blood, which is used to make sure medical products aren't contaminated. Their blood contains coagulogen, a chemical that can be used to detect bacteria.

The Atlantic States Marine Fisheries Commission voted this month to propose taking into account the death toll associated with medical harvesting when determining how many horseshoe crabs can be harvested from the Delaware Bay.

The medical harvest is about 500,000 crabs per year.

The crabs are also harvested by fishermen for bait. The value of the commercial harvest of horseshoe crabs grew from about $400,000 in 2004 to more than $1.8 million in 2014.