LAUSR

There are many pathways by which invasive species are introduced and become established, with the exotic pet trade becoming an increasingly important route. The abandonment of pets is a growing problem, which has been recognized widely and that has provoked some legislative responses. We developed an approach to deal with the abandonment issue that is more comprehensive than existing frameworks. We analyzed a substantial data set on exotic fish, crayfish and herptiles in northeastern Spain to illustrate the approach and its rationale. Spanish legislation mirroring the recently enforced European Strategy to control invasive species was introduced in 2011, and we analyzed information from 2009 to 2018 to assess the effectiveness of the legislation. The 2011 legislation was intended to ban the sale of a prioritized list of invasive species in retailers, which aimed to reduce the release of exotic species into recipient ecosystems. We did not see any prohibited species for sale in retailers after 2011. However, 60,753 exotic animals from 4 classes, 10 orders, 47 families and 139 species were recorded in Barcelona and elsewhere in northeastern Spain, including 134 species other than the 5 prioritized invasive species. We found little evidence of a change in exotic pet releases into urban lakes after 2011. Invasive terrapins (Trachemys spp.) were captured in urban lakes and were the most prevalent taxon in a herptile rescue centre with increased numbers after 2011. We advocate a four-tier approach to deal more effectively with the pet-abandonment issue, which includes: (1) better understanding of uncertainties in the listing of potentially invasive species; (2) allowing would-be owners to seek accreditation (through training); (3) pit-tagging to ensure that animals can be associated with registered owners, including species now prohibited but that had been traded for decades; and (4) ensuring that adults of low-cost, small-size-at-purchase species are present at the point-of-sale to ‘warn against’ the consequences of impulsive purchases.