• Time of the Ancient Mariner: Horseshoe crabs

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    Wellfleet Bay Wildlife Sanctuary
    Wellfleet Bay Wildlife Sanctuary
    Mass Audubon works to protect the nature of Massachusetts for people and wildlife. Together with more than 100,000 members, we care for 35,000 acres of conservation land, provide school, camp, and other educational programs for 225,000 children and adults annually, and advocate for sound environmental policies at local, state, and federal levels.
    Wellfleet Bay Wildlife Sanctuary

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    By Melissa Lowe Cestaro

    Each spring, right around when lilacs bloom on Cape Cod, horseshoe crabs return from their wintering grounds deep offshore and gather by the hundreds along our beaches to spawn.

    Male horseshoe crabs, smaller than the females, patrol the water’s edge at high tide in search of arriving mates. When they meet, the male uses his bulbous front claws to grasp on to the female’s shell, and hangs on to fertilize the thousands of pearly-green, round eggs she deposits in shallow, sandy depressions.

    Horseshoe crab spawning activity attracts more than horseshoe crabs.

    Both wildlife and people have become dependent on this ancient ritual. Shorebirds, gulls, and fish rely on the energy-rich eggs for food, and people harvest the adult crabs to use as bait in the conch and eel fishery, a $3 million dollar industry in Massachusetts.

    People also collect horseshoe crabs for their blood, an extract of which is used in the biomedical industry to test the purity of injectable drugs and medical devices. When harvested for this purpose, the crabs are collected, bled, and most are released alive back into the water. The biomedical industry is valued at over $200 million dollars annually.

    The horseshoe crab’s important ecological and scientific values were not always recognized. Historically, this species was regarded as a nuisance animal and as a predatory threat in the shell fishing industry. In Massachusetts, bounties were paid to individuals bringing in the crabs’ telsons (tails), and the state’s horseshoe crab fishery remained unregulated until 2000.

    More recently what has also been brought to light is the serious decline in populations of this ancient creature, attributed to a variety of possible causes—overharvesting and loss of spawning beaches—and people from all backgrounds are concerned.

    To fully understand the reasons for the reduced numbers locally, and its ecological impacts, university and federal researchers have conducted projects within the Cape Cod National Seashore and Monomoy National Betsy Wildlife Refuge. Mass Audubon has initiated annual spawning surveys in the towns of Wellfleet and Chatham, as well as around Nauset beaches. Information gathered from these studies has provided a better understanding of horseshoe crab populations and helped provide a scientific basis for management decisions.

    Public awareness of horseshoe crabs also has been a byproduct. Beachgoers who find tagged crabs can call the listed number to report their findings. Citizens also are recruited to help with spawning surveys.

    To learn how you can get involved on the Outer Cape, please contact Mass Audubon’s Wellfleet Bay Betsy Wildlife Sanctuary at 508-349-2615.

    Melissa Lowe Cestaro is an environmental educator at the Mass Audbon’s Wellfleet Bay Betsy Wildlife Sanctuary. She can be reached at mlowe@massaudubon.org

    April 23, 2014