More than 800 species of bivalves harvested by humans tend to be more resistant to extinction

Seafood enthusiasts from around the world are harvesting over 800 varieties of bivalves, expanding the range of known species that are exploited by humans.

In a new study, scientists Stewart Edie from the Smithsonian, Shan Huang from the University of Birmingham, and their colleagues significantly expanded the list of bivalve species (clams, oysters, mussels, scallops, etc.) known to be collected by humans. They identified the characteristics that make these species prime targets for collection and also found that some of these same traits have made these bivalve groups less prone to extinction in the past and could protect them in the future.

The research, published in Nature Communications, found that humans exploit around 801 species of bivalves. This number adds 720 species to the 81 listed in the United Nations Food and Agriculture Organization (FAO) database, highlighting the enormous diversity of bivalves known to be collected and used by humans.

Areas with Higher Vulnerabilities

The study identified global “hotspots” where bivalve exploitation occurs, reporting certain areas where there is a higher vulnerability to overexploitation and includes a list of species at greater risk.

The study authors pointed out certain oceanic regions, such as the East Atlantic and the northeast and southeast Pacific, as areas of special interest for management and conservation.

Edie, who serves as the curator of fossil bivalves at the National Museum of Natural History, stated that fortunately, many of the features that make these bivalve species appealing to humans have also reduced their risk of extinction.

Specifically, bivalve species inhabit a variety of climates worldwide, with a wide range of temperatures. This adaptability promotes resilience against natural extinction factors. However, human demand for these species can place them and the ecosystems they are part of at greater risk of destruction.

“We are fortunate that the species we consume also tend to be more resistant to extinction,” said Edie. “But humans can transform the environment in the blink of a geological eye, and we need to manage these species sustainably so that they are available for future generations.”

“It’s somewhat ironic that some of the traits that make bivalve species less vulnerable to extinction also make them much more attractive as a food source, as they are larger and are found in shallower waters over a wider geographic area,” said Huang.

“Hence, human influence can disproportionately eliminate the strong species. By identifying these species and making them globally recognized, responsible fishing can diversify the collected species and prevent oysters from becoming the dodos of the sea.”

Bivalve mollusks such as clams, oysters, scallops, and mussels have filtered water and nourished humans for millennia. In places like Estero Bay, Florida, the indigenous Calusa tribe sustainably harvested approximately 18.6 billion oysters and built an entire island and 30-foot-high mounds with their shells.

Bivalve Species at Risk

But the history of humans harvesting bivalves is also fraught with examples of overexploitation, largely by European colonizers and mechanized commercial fishing, which led to the collapse of oyster populations in places like the Chesapeake Bay, San Francisco Bay, and Botany Bay near Sydney, Australia.

After studying scientific literature and realizing there was no comprehensive list of all species known as fishing targets, Edie and his co-authors set out to document the variety of bivalves used by humans.

After compiling all the species they found mentioned in over 100 previous studies, the researchers began to investigate possible similarities and patterns among the 801 bivalves on the list. The team examined what traits allow humans to exploit a bivalve and how those traits relate to their risk of extinction.

The study found that humans tend to collect bivalves that are large-bodied, found in shallow waters, inhabit a wide geographic area, and survive across a broad range of temperatures. These last two traits also make most exploited bivalve species less susceptible to the pressures and extinction risks that have eliminated species from the fossil record in ancient times.

The researchers hope that their data will improve conservation and management decisions in the future. Specifically, their list identifies regions and species as particularly prone to extinction. Similarly, the list can help identify species that require further study to assess their current extinction risk.

In this regard, the researchers identified the top ten species at risk, including oysters found off the coasts of Malaysia and the Philippines, scallops from the Gulf of Mexico, and clams found off the Atlantic coast of Central Africa.

Table 01. Top 10 species at greatest risk of extinction.

Furthermore, Edie stated that he wants to use the characteristics associated with exploited bivalves to investigate bivalve species that are currently not known to be captured by people.

“We want to use what we learned from this study to identify the bivalves that are being harvested and that we don’t yet know about,” said Edie. “To effectively manage bivalve populations, we need to have a complete picture of the species people are harvesting.”

This research is part of the museum’s Ocean Science Center, which seeks to catalyze change and action by advancing knowledge of the ocean and sharing it with the scientific community, policymakers and the general public. The research also supports the Smithsonian’s Life on a Sustainable Planet initiative, a major effort to collect new data about the changing planet, implement holistic and multi-scale approaches to environmental conservation and educate the world about why and how sustainable solutions to climate change can benefit people and nature.

This research was supported by the Smithsonian, the German Research Foundation, the National Aeronautics and Space Administration and the National Science Foundation.

Reference (open access):
Huang, S., Edie, S.M., Collins, K.S. et al. Diversity, distribution, and intrinsic extinction vulnerability of exploited marine bivalves. Nat Commun 14, 4639 (2023). https://doi.org/10.1038/s41467-023-40053-y