Wednesday, June 15, 2016

Horseshoe Crab Harvesting


The past month was the time when horseshoe crabs were once again in the news as their egg-laying on the Delaware beaches in New Jersey once again coincided with the arrival of shorebirds that rely on those eggs for sustenance during their migration. Late spring and early summer are the peak Horseshoe Crab mating and spawning time.

Horseshoe crabs are marine arthropods that will be seen throughout the year on New Jersey beaches and bays. We commonly find crabs that are dead and have washed up on the shore. Kids are fascinated by their unusual shape.

Horseshoe Crabs may look like a crustacean, but they are actually a closer relative of spiders and are classified with Arachinda along with scorpions and ticks.

The species found in NJ, limulus polyphemus, is distributed from the coasts of northeastern Maine to Mexico.

They are commonly referred to as “living fossils” that outlasted the dinosaurs and are probably the distant relatives of the more ancient trilobites and Eurypterida or sea scorpions that existed from the Cambrian period 520 million years ago to the Permian 240 million years ago.

The horseshoe crab's threatening-looking spike-shaped tail is not a defensive poisonous stinger. This tail or telson is an adaptation to upright itself after landing in its back or used in steering when swimming upside down underwater.


The ventral side of a horseshoe crab with 5 pairs of walking appendages and overlapping book gills
via Flickr

Horseshoe crabs are harvested as bait. Each year, half a million horseshoe crabs are captured and bled alive. A chemical found in their blue blood is unique. This chemical is found only in the amoebocytes of its blood cells and it can detect mere traces of bacterial presence and trap them in inescapable clots. Pharmaceutical companies use that coagulogen to detect contamination in any solution that might come into contact with blood.

We can question whether or not this bleeding is humane to horseshoe crabs, but we know that the number of horseshoe crabs is decreasing dramatically. Even more so than the medical industry, fisherman use far more horseshoe crabs as bait. They are commonly used in traps meant to catch American eel and conch.

Millions of horseshoe crabs every year as bait. By comparison, the medical industry uses a few hundred thousand horseshoe crabs each year, and the vast majority are returned to the ocean and probably survive.



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