Can the native crab Thalamita danae be an effective biological control agent of the invasive mussel Xenostrobus securis in Hong Kong?

Abstract

AbstractLocal predators are often considered effective and environmentally-friendly control agents to limit invasive species. Such biological control, however, depends on both the predator prey preferences and performances, which are in turn affected by variations in the physical environment. This study investigated the predation of the swimming crab Thalamita danae on the invasive mussel Xenostrobus securis under different salinity and thermal conditions. Xenostrobus securis, which is native to Australia, has spread to Hong Kong since the last decade, causing adverse ecological and economic impacts. Laboratory experiments evaluated the prey preferences and feeding behaviours of the crab on both the native mussel Brachidontes variabilis and the invasive X. securis under different typical salinities (15, 25, and 35‰) and temperatures (22 and 28 °C). The crab did not show clear preference toward either the invasive or the native mussels. Although the shell morphology of the invasive mussels lowered handling time as compared to the native mussels, the crab consumption rate was similar between the mussel species. The survival and predation rate of the crab were, however, substantially reduced under low salinities (< 15‰) where X. securis could be found. Thalamita danae, therefore, is a potential predator of X. securis, but such predation is only possible under normal, oceanic conditions. In hyposaline, estuarine/ freshwater environments where X. securis can survive, however, T. danae performs poorly and, as a result, such physical conditions may represent a predator refuge for the mussels to invade local ecosystems.