The ‘killer shrimp’ Dikerogammarus villosus (Crustacea, Amphipoda) invading Alpine lakes: overland transport by recreational boats and scuba‐diving gear as potential entry vectors?

Abstract

ABSTRACTThe alien freshwater amphipod of Ponto‐Caspian origin, Dikerogammarus villosus, also known as the killer shrimp, is recognized as being one of the worst invasive alien species in Europe, representing a major conservation problem.Recently, the species has been reported to invade lakes in the Alps in putative association with overland transport linked with recreational activities.This study provided a method to assess risk associated with this overland transport and an opportunity to set up a rationale for effective preventive conservation management.A field survey of 60 lakes encompassing all the Alpine area has revealed the presence of killer shrimp in 12 lakes. Subsequent multivariate data analysis showed that the occurrence of the amphipod was associated predominantly with large lakes at low altitudes and high recreational boating activity, always inhabited by the invasive zebra mussel (Dreissena polymorpha). The distribution pattern of killer shrimp was not associated with water conductivity and pH.Laboratory experiments demonstrated that, compared with two other amphipods Gammarus pulex and G. roeselii, killer shrimp seems to attach itself more effectively to ropes used by boaters, as well as diving wetsuits. They remained attached to the ropes even while being strongly shaken for 5 min (mimicking movements associated with overland transport). Moreover, the species is able to survive up to three and a half days out of water, between the layers of diving wetsuits.These results show that even in isolated Alpine lakes there is a high risk of overland spread of killer shrimp by recreational boats and diving wetsuits. Thus, even simple measures such as mechanical cleaning and washing of water sports gear would greatly reduce such risk. Copyright © 2013 John Wiley & Sons, Ltd.