Demon Shrimp

The demon shrimp (Dikerogammarus haemobaphes) is a small shrimp-like amphipod crustacean. As a close relative of another highly invasive species (the killer shrimp, Dikerogammarus villosus), demon shrimp are able to survive in a wide variety of salinities, from fresh water to brackish water. They are also found living within a wide range of temperature and substrate habitats, although they prefer to live in coarse grained gravel substrates or on top of muscle shells such as that of the zebra mussel (Dreissena polymorpha). With 2-3 generations per year, each consisting of 3-5 cohorts of between 20-50 eggs per brood, demon shrimp breed quickly in large numbers. Demon shrimp are omnivorous, feeding on detritus, algae and other small aquatic invertebrates.

Native to the Ponto-Caspian region, the demon shrimp has been spreading throughout Europe for over 20 years. With rapid growth rates, early maturation and high fecundity, in addition to their tolerance levels for a variety of different environments, demon shrimp are well suited to successfully invading new habitats. First found in Hungary, Austria, Belgium, Germany, Poland, Russia and Ukraine, it was first recorded in the River Severn in the UK in 2012 and has since spread widely across the UK.

At one site on the River Churnet, Staffordshire Wildlife Trust carried out three-minute kick samples regularly. After no demon shrimp were recorded in January 2014, 442 were recorded in October 2016 after a very rapid invasion occurred throughout 2015. The speed in which populations of demon shrimp can become established in new environments is one of the characteristics that allow them to be successful invaders. In addition to the demon shrimp, other invasive species from the Ponto-Caspian region have previously become established within the UK such as the tube building corophiid amphipod (Chelicorophium curvispinum) and the killer shrimp (D. villosus). Often interactions between species can facilitate each other, aiding with the establishment of an additional new species.

Through direct predation, increased competition for resources and the addition of new diseases and parasites into the ecosystem, demon shrimp can cause significant damage to native species. The increased presence of the demon shrimp in UK waters has coincided with the decline of the native freshwater shrimp (Gammarus pulex) and several mayfly and caddisfly species. In some ecosystems, such species are now locally extinct. Plants, insects, fish, mammals and birds all rely on the various fly species as a food source, causing severe knock on effects across the food chain and habitat when they are removed. In addition, native freshwater amphipods, such as Gammarus pulex, are considered key to leaf litter processing within UK rivers. With a lower survival rate of G.pulex due to predation by the demon shrimp, leaf litter processing and recycling may be reduced, disrupting natural cycles in the rivers.

• Avoid stepping into the water – this can stir up sediment, throwing up sediment DNA and any inhibitory molecules present. Sediment may clog the filter and prevent sufficient volumes of water being filtered.
• Highly important to adhere to biosecurity protocols and take this into consideration during survey design to prevent the spread of Dikerogammarus eggs on clothing and equipment.