SEAFOOD EXTINCTION RISK ESTIMATED FROM BIOGEOGRAPHY AND THE FOSSIL RECORD: MARINE BIVALVES IN PERIL

Bivalves underpin a global fishery supporting many businesses and households, and are under threat from overfishing, habitat destruction, and climate change like many other marine animals. We compiled a database of exploited shallow-marine bivalves and explored patterns of their biology and geographic distribution. We then assessed the intrinsic extinction risk of exploited species in relation to other bivalves using the Paleontological Extinction Risk In Lineages (PERIL) score (Collins et al 2018, Proc B), which is based on present-day geographic range size, realized thermal tolerance (from sea surface temperature), and lineage extinction history in the fossil record.

Compared to the other ~5000 bivalve species, the 547 exploited species tend to have large shells and live at shallowest waters (after controlling for phylogeny), which presumably increases their accessibility. Globally, the number of exploited species (in a 50*50 km² grid cell) is highest in the tropical west Pacific where the overall bivalve species richness peaks, whereas the proportion of exploited species is highest in the temperate west coasts of both New and Old Worlds.

Because exploited species tend to have wide geographic and temperature ranges, their overall intrinsic risk of extinction tends to be low, even when they belong to families with a history of higher extinction rates during the Cenozoic. Still, a number of exploited species are prone to extinction: 180 species have PERIL scores higher than the global median, 34 are in the top 20%, 8 in the top 10%, and two exploited oyster species are even in the top 5% of PERIL scores across all of Bivalvia. Worldwide, the vulnerable exploited species are concentrated in tropical regions, including the tropical west and east Pacific. The tropical east Pacific also has a large number of extinction-prone bivalve species in general, thus might be prioritized for biodiversity conservation. Global maps of anthropogenic pressures suggest that some regions having moderate average PERIL scores harbor exploited species potentially at risk; and that some regions and clades are especially vulnerable. Collectively, our findings demonstrate how combining paleontological, biogeographic and ecological data can help inform the management of global marine resources.