The freshwater bivalve Corbicula fluminea, native to Southeast Asia, has invaded many fresh waters of the World. The mollusk can often reach extremely high densities of several hundreds to thousands of individuals per square meter within invaded rivers, canals or lakes. 

As many other invasive bivalves, it can also experience rapid die-offs due to extreme abiotic conditions, including both drought and flooding, as well as high and low temperatures. Such mass mortalities of Asiatic clams regularly occur during heat wave events within flowing waters of the Tarn river (France), leading to the release of many clam shells and dead soft tissues floating on water.

Here, we observed that the concentration of floating soft tissues from Corbicula fluminearesulted in aggregation of many European catfish (Silurus glanis) individuals. In June 2019, we identified up to 100 catfish individuals (ranging from 50 cm to more than 200 cm long) concentrating within a 200-m long river stretch of the Tarn river to consume floating dead clam soft tissues.

Such an opportunistic feeding behavior is another example of the amazing ability of the European catfish species to adapt to novel food resource opportunities. This observation illustrates how feeding bivalves can cause foodweb alterations through direct benefits to scavenging species such as European catfish.