The recently introduced bivalve Xenostrobus securis has higher thermal and salinity tolerance than the native Brachidontes variabilis and established Mytilopsis sallei

The recently introduced bivalve Xenostrobus securis and the previously introduced Mytilopsis sallei (~ 30 years) are dominant over the native Brachidontes variabilis in estuarine fouling communities in Hong Kong. This study tested whether these introduced species have higher thermal and salinity tolerance than the native species under local subtropical seawater conditions. Survival, attachment, clearance rate and byssal thread production of these three species were examined through 96-h acute temperature and salinity tests. The results indicated that X. securis responded normally over a wide range of temperature and salinity conditions. Though M. sallei exhibited a wide salinity tolerance, its sub-lethal responses decreased in cold-seawater conditions. Brachidontes variabilis had the narrowest tolerance to temperature and salinity. These findings may explain the dominance of the non-native bivalves over B. variabilis. The high tolerance of X. securis enables them to become highly invasive in subtropical regions across Southeast Asia, impacting natural communities and shellfish farming.