When invasions go unnoticed: Public perception of the freshwater jellyfish Craspedacusta sowerbii in Europe

Biological invasions are a major driver of biodiversity loss, yet inconspicuous or “cryptic” species often escape detection and public awareness, limiting management responses. We investigated the freshwater jellyfish Craspedacusta sowerbii, likely native to China and now present on six continents, through a 22-month multilingual online survey across 17 European countries (n = 1388), to assess public knowledge, perceptions and views on its management. Results revealed low public awareness: over 80% of respondents did not know the scientific name, 49% misidentified its freshwater habitat as marine and only 33% recognized it as non-native. Aesthetic perceptions were largely positive, but mass occurrences triggered caution and direct contact was rare and usually harmless. Bayesian Network analysis showed that direct observation—rather than demographic factors or scientific knowledge—was the strongest predictor of concern and support for public discussion. While C. sowerbii was not widely perceived as a local threat, many respondents acknowledged its potential ecological implications and supported greater public awareness and management actions. Our findings highlight how visual subtlety and limited media coverage reduce detection and prioritization of cryptic invasive alien species (IAS), hindering early warning systems and policy development. Leveraging citizen science and experiential engagement can improve recognition and reporting, complement formal monitoring and support more inclusive management strategies. We recommend integrating cryptic invasions like that of C. sowerbii into IAS frameworks and policies, emphasizing public participation and awareness to address overlooked, but potentially impactful species. Read the free Plain Language Summary for this article on the Journal blog.