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Shedd Aquarium’s Queen Conch Study—A Holistic Approach to Counting an Endangered Marine Invertebrate

This, my second article highlighting current field research initiatives of Chicago’s Shedd Aquarium, is a look at one of the two most important fisheries in the Bahamian Archipelago—and efforts to address the decline of a shellfish population that has been harvested since Pre-Columbian times. 

Conch_body
Queen Conch

Dr. Alexander Tewfik, a post-doctoral fellow at Shedd’s Daniel P. Haerther Center for Conservation Research, has embarked on a three year project to study Bahamian queen conch (Strombus gigas) populations using non-traditional surveys. He hopes the research will contribute to improved management and conservation of Queen conch that is vital to marine ecosystems and an array of human stakeholders.

I once owned a conch shell that I purchased as souvenir while visiting Haiti on a vacation with my family. I was wholly unaware that the inanimate seashell was called a “conch” until I read Lord of the Flies. Even then, I probably mispronounced the word “conch”, which is supposed to be pronounced with a hard “K”, and more aptly used in reference to one of the six Caribbean region species of large marine gastropods and their shells.  Lastly, I had no idea that I was helping deplete a population of a highly prized invertebrate species—the largest of the six species in this region— that is listed under CITES Appendix II (commercially threatened).

The marine snail and its shell is what really comprises this megagastropod in its entirety; however, some times the empty shell alone is referred to and colloquially better known as a conch, as it was in the book Lord of the Flies.  It never occurred to me that a snail actually lived inside the shell until I took an elective high school course in invertebrate zoology.  Perhaps you are more astute than I, but it would seem that most people, even avid beach-goers, are more familiar with the calcium carbonate shells than the muscular, fleshy part of the organism—which includes the part we call the mantle. The mantle, or outer epithelium of the snail’s living tissue, is what secretes the calcium carbonate and the protein conchiolin, which comprise the inner and outer layers of the shell.

Conch_seagrass
Seagrass

Shells of the queen conch have been sold as decorative souvenirs, or curio, for many years, and the soft tissue of the snail has been a food source since pre-Columbian times. Since the mid-20th century, harvesting for expanding local populations, tourists and international export has increased pressure on populations of Queen conch throughout the region.  Unfortunately, in the past few decades the queen conch has been so overharvested that they are no longer abundant in shallow coastal waters where they once thrived. Hence, marine biologists and conservationists are quite concerned about the future of this marine snail and the wider natural community where it lives. In recognition of declines of Queen conch and its cultural importance, the Government of the Bahamas, led by the Bahamas National Trust, has embarked on a Conch conservation campaign to be officially launched in Nassau on April 27th, 2013.

Herbivorous queen conchs indirectly manage seagrass ecosystems, eating dead grass and creating conditions that support a broader biodiversity. Healthy sea grass beds provide important ecosystem services: they buffet the coast from storm waves, stabilize sand that might otherwise smother coral reefs, and support critical nursery and foraging habitat for lobsters and fish. Anyone who’s ever appreciated the beauty of a coral reef, whether in pictures or in person, actually owes a debt of gratitude to sea grasses and one of the principle animals, Queen conch, which facilitates healthy beds: one cannot thrive without the other.

Fortunately, under the auspices of the Shedd, Dr. Tewfik has endeavored to take a new approach to understand the ecosystem-wide impacts that overharvesting conch may catalyze, in hopes of supporting sustainable management. Instead of counting conch along set transect lines (a significant effort being conducted by the NGO Community Conch and Shedd’s mutual partners the Bahamas National Trust and Bahamas Department of Marine Resources), the biologist plans to assess the abundance of other types of benthic consumers from specialized grazers to predatory snails such as helmet shells—themselves part of the curio trade- for a broader community perspective.  He also plans to document the conditions of seagrass habitat so vital to Queen conch and associated biodiversity across the archipelago. In addition, Dr. Tewfik will assess whether juvenile and adult conch spillover from protected areas like Exuma Cays Land and Sea Park may help replenish adjacent fished areas.

According to the Shedd Aquarium, this holistic approach to resource management and conservation will provide significant input to adaptive management strategies for exploited species; the development of protected areas and/or fisheries reserves that enhance a broad set of species and habitats; and identify ecosystem conditions that no longer support sustainable harvests, high biodiversity, and healthy habitats.

Comments

  1. Lee Dickey
    University of Waterloo
    April 9, 2013, 10:14 pm

    This is important work. Congratulations on a splendid article.