Britain’s rivers and lakes are facing an increasing threat from two highly invasive freshwater crustaceans that many anglers may never even notice beneath the surface — the killer shrimp (Dikerogammarus villosus) and the demon shrimp (Dikerogammarus haemobaphes). Although small in size, these aggressive invaders are capable of causing major disruption to aquatic ecosystems, threatening fish stocks, biodiversity and the health of our waterways.
Both species originate from the Ponto-Caspian region of Eastern Europe and are believed to have arrived in the UK through international shipping and interconnected European waterways. Since their arrival, they have spread rapidly through canals, reservoirs and river systems, often transported unknowingly on boats, trailers, fishing tackle and wet clothing.
The killer shrimp is widely regarded as one of Europe’s most destructive aquatic invasive species. Larger and more aggressive than our native freshwater shrimp, it is a voracious predator that feeds on insect larvae, fish eggs, small crustaceans and even other shrimp species. The demon shrimp, although slightly smaller, behaves in a similar way and is equally capable of dominating freshwater habitats once established.
For anglers, the ecological consequences are significant. Healthy fisheries rely on balanced food webs, and native freshwater shrimp play an important role as prey for trout, grayling, perch and juvenile salmonids. When invasive shrimp arrive, they outcompete and displace native invertebrates, reducing biodiversity and altering the natural food chain.
Initially, some fish species may benefit from the abundance of the larger invasive shrimp as a food source. However, this short-term gain can mask wider ecological damage. Killer and demon shrimp consume huge numbers of aquatic insects and fish eggs, potentially affecting recruitment of sensitive fish species over time. In waters already under pressure from pollution, habitat loss and climate change, invasive shrimp add another serious challenge.
One of the greatest concerns is the speed at which these species spread. They reproduce rapidly, tolerate poor water quality and survive in a wide range of environmental conditions. Even more worrying is how easily they are transported between waters. A few individuals trapped in the folds of a keepnet, livewell, anchor rope or damp waders can establish a new population in another catchment.
Preventing further spread now relies heavily on anglers, boaters and all water users adopting strict biosecurity measures. The Environment Agency and conservation groups continue to promote the “Check, Clean, Dry” approach:
- Check equipment, clothing and boats for mud, plants and animals.
- Clean everything thoroughly with hot water or disinfectant.
- Dry all equipment completely before visiting another waterbody.
These simple precautions are among the most effective ways to slow the spread of invasive species.
Awareness is equally important. Many anglers remain unfamiliar with the differences between native shrimp and these invasive species. Learning to identify them and reporting suspected sightings can help environmental authorities monitor their spread and protect vulnerable fisheries.
Our rivers are already facing unprecedented environmental pressures. Protecting them now requires vigilance not only against pollution and habitat destruction, but also against invasive species capable of silently reshaping entire ecosystems. For the angling community, good biosecurity is no longer optional — it is an essential part of safeguarding the future of our sport and the health of Britain’s waterways.
Identifying Freshwater Shrimp Species
Native Freshwater Shrimp
Key Features
- Smaller size (typically 1–2 cm)
- Pale brown or translucent colour
- Smooth curved body
- Less aggressive appearance
- Found naturally in clean rivers and streams
ID is best carried out with a magnifying glass or zooming in with a phone camera.
Demon Shrimp
Key Features
- Similar shape to killer shrimp but usually smoother
- Often reddish or orange colouring
- Slightly smaller than killer shrimp
- Aggressive scavenger and predator
- Can carry parasites harmful to native species
ID is best carried out with a magnifying glass or zooming in with a phone camera.
Killer Shrimp
Key Features
- Larger and more robust than native shrimp
- Distinct striped or banded appearance
- Hairy body and legs (“villosus” means hairy)
- Powerful curved claws
- Aggressive predatory behaviour
ID is best carried out with a magnifying glass or zooming in with a phone camera.
Reporting Invasive Shrimp Species in the UK
Identification is best carried out with a magnifying glass or zooming in with a phone camera.
If you find either a Demon or Killer Shrimp in the UK then please report using one of the invasive species reporting apps;
- INNS Mapper
- iRecord
- iNaturalist
Make sure that you get clear photographs of the invertebrate, you should should also destroy the shrimp rather than return it to the water.
Further Resources and Information
- The Angling Trust have more information on invasive species and their control, they also manage the Angling Improvement Fund from the EA to help clubs control invasive species https://anglingtrust.net/invasive-non-native-species/
- NBN Atlas hold all the reported records for invasive species in the UK https://nbnatlas.org/
- GB Non Native Species Secretariate hold a wealth of information about not native species https://www.nonnativespecies.org/