Assessing shorebird mortalities due to razor clam aquaculture at key migratory stopover sites in southeastern China.

Aquaculture sometimes provides foraging habitat for certain bird species, but it can also reduce foraging habitat for other birds or result in intentional and accidental mortality. Here, we report a significant and previously unrecognized conflict between razor clam (Sinonovacula spp.) farming and the conservation of declining shorebird species in southeastern China. We surveyed 6 out of 11 internationally important stopover sites for shorebirds in Fujian and Zhejiang provinces and found large expanses of intertidal foraging habitat covered by nets to prevent waterbirds from feeding on young razor clams at two sites, Xinghua Bay and Yueqing Bay. We conservatively estimated that 13,676 (2.5 th - 97.5 th percentile values: 8,330 - 21,285) individual shorebirds were caught in the nets at these two sites in April and May 2021, including at least two Endangered and seven Near-threatened species. We also estimated species-specific mortality for five species and found that their populations may be strongly affected by this mortality. We visited an additional 33 sites in coastal Zhejiang and Fujian provinces that exhibited similar, remotely sensed mudflat structure to our two study sites and found netting at 17 of them, suggesting that razor-clam farming poses a widespread threat to shorebirds in southeastern China. Although razor clams are typically harvested in late March to early April, the nets were left on the mudflats throughout the spring and summer, including when the bulk of shorebird migration takes place. Immediately removing these nets after the young clams are harvested could prevent most of the spring mortality of shorebirds, although this is unlikely to happen without government regulations or economic incentives directed towards aquaculture operations. We also propose a research agenda to more thoroughly assess the impact of razor clam aquaculture on shorebirds and vice versa, and to devise more effective ways to mitigate shorebird mortality. This article is protected by copyright. All rights reserved.