Time-series analysis of a native and a non-native amphipod shrimp in two English rivers

The Ponto-Caspian amphipod Dikerogammarus haemobaphes, known as the demon shrimp, arrived in the UK in 2012 and has since spread rapidly, invading waterways particularly in central England. In this paper we use data from routine Environment Agency surveys to explore how D. haemobaphes has spread and assess whether it fits the 2013 predictions of Gallardo and Aldridge, which identified southern, eastern and central England as most vulnerable to Ponto-Caspian invaders. We then focus on two rivers, the Thames and the Trent, utilising a mixture of recent and long term datasets to track the presence of D. haemobaphes along the course of each river and compare it to that of the native amphipod Gammarus pulex. We observed that D. haemobaphes is now the dominant amphipod in the navigable stretches of both rivers and that the spread of the species nationally appears closely linked to the canal network. We suggest that focussing biosecurity controls on the movement of boats and equipment between affected and unaffected catchments will be key to limiting the further spread of this and similar invasive species.