SI on economic costs of invasions - Feeling the pinch: global economic costs of crayfish invasions and comparison with other aquatic crustaceans

Despite voluminous literature identifying invasive species impacts, understandings of monetary costs remain limited. Recently, profound impacts have been attributed to invasive crustaceans, but associated monetary costs lack synthesis. Here, we analyse globally reported costs of invasive freshwater crayfish across taxonomic, spatial and temporal descriptors. Moreover, we compare their cost magnitude to other invasive crustaceans — crabs, amphipods and lobsters. Between 2000 and 2020, crayfish caused US$ 1.28 billion in reported costs; the vast majority (95%) attributed to Astacidae (principally the signal crayfish Pacifastacus leniusculus) and the remainder to Cambaridae. According to reports, crayfish costs mostly impacted European economies (US$ 1.23 billion), followed by costs reported for North America and Asia. Despite well-known damages caused by invasive crayfish, costs were unreported elsewhere, highlighting knowledge gaps and challenges in cost quantifications. Invasive crayfish costs increased exponentially in the last two decades, averaging at US$ 61 million per-annum. Invasive crabs caused costs of similar magnitude (US$ 1.25 billion; US$ 53 million per-annum) but were mostly confined to North America (95%). Damage-related costs dominated for both crayfish (83%) and crabs (99%), with management spending lacking. Reported economic impacts from amphipods (US$ 178.8 thousand) and lobsters (US$ 44.6 thousand) were considerably lower. We identify burgeoning economic costs from these invasive groups yet highlight pervasive knowledge gaps at multiple scales. Further cost reporting is required to better-ascertain the true scale of monetary costs caused by invasive aquatic crustaceans.