The pet and horticultural trades as introduction and dispersal agents of non-indigenous freshwater molluscs

Understanding the introduction pathways and patterns of distribution of non-indigenous species is essential for minimizing future invasions. In the aquarium and aquatic ornamental plant trades lies the potential for importing freshwater molluscs and dispersing them. We surveyed 37 pet shops and 24 aquatic plant nurseries throughout Israel in search for freshwater molluscs. The survey yielded 29 taxa, of which 15 are offered for sale (deliberate introduction) and 14 are stowaways (accidental introduction). The species offered for sale are alien species not yet established in Israeli natural systems, whereas the stowaways are mainly established species that have already invaded and maintain stable populations in natural habitats. Six species were documented for the first time in Israel. Taxon richness was not correlated with any geographic or socioeconomic variable. We attribute this to the small size of Israel, which enables people from different locations and social classes to travel easily across the country to buy plants or pets. The findings of this study imply that the import of freshwater molluscs deliberately for commerce or on aquatic plants as stowaways is an important mode of introduction for these species. In order to prevent, or at least reduce, the extent of this phenomenon, we recommend establishing more effective restrictions on the import of live material, preventing deliberate import and commerce of freshwater molluscs, and confiscating and eliminating non-indigenous freshwater molluscs once found, before they reach nature.