Killer shrimp (Dikerogammarus villosus)

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Killer shrimp

Top facts

  • The killer shrimp is a highly invasive species, and is considered to be one of the most successful invaders of freshwater systems.
  • Discovered in the Ponto-Caspian basin of Europe, the killer shrimp has since become established in 17 European countries.
  • The killer shrimp is a voracious predator and has a varied diet, including shrimps, young fish, fish eggs and insect larvae.
  • The killer shrimp is capable of expanding its range 124 km per year.
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Killer shrimp fact file

Killer shrimp description

KingdomAnimalia
PhylumArthropoda
ClassMalacostraca
OrderAmphipoda
FamilyGammaridae
GenusDikerogammarus

Considered to be one of the most successful invaders of freshwater systems (4), the killer shrimp (Dikerogammarus villosus) was only discovered as recently as 1989, in an Austrian stretch of the river Danube (5).

A large amphipod species which can grow up to 30 millimetres in length (2) (6), the killer shrimp has a curled body, two pairs of antennae (1) and relatively large, powerful mandibles (1) (2). This species is semi-transparent (1) and variable in its colouration (6), and can be striped, spotted or uniform in pattern (2) (6). Male killer shrimps tend to be longer than females (6).

Juvenile killer shrimps are small compared to the adult length (6), only being about 1.8 millimetres long when they hatch (1). Newly hatched young resemble the adults in appearance (1).

Size
Adult total length: up to 30 mm (1) (2)
Newly hatched young length: 1.8 mm (1) (3)
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Killer shrimp biology

As its name suggests, the killer shrimp is a voracious predator (2), and is known to kill a wide range of native species in the areas in which it is invasive (2) (5). Its diet includes other amphipods, shrimps and crayfish, as well as young fish, fish eggs (1) (2) (3) (4) (5) (7) and insect larvae (5). The killer shrimp is an omnivorous species (3), being known to also eat various types of algae (5), and has a variety of feeding habits, including shredding, grazing and even coprophagy (5). Various fish species, including trout and perch, predate the killer shrimp (1) (3).

Reproduction in the killer shrimp begins when the water temperature reaches about 13 degrees Celsius (1). Although this species is thought to breed throughout the year (6), there are reported to be three reproductive peaks (1) (6), with the highest level of reproduction occurring in April and May when food is readily available and water temperatures are favourable (1).

The killer shrimp has a high reproductive potential, as it is quick to reach sexual maturity (5), and so only a few individuals are needed to rapidly establish a new population (6). This species grows extremely quickly throughout its life (5) (6), reaching growth rates of up to 2.6 millimetres in just 2 weeks during the spring (6). Female killer shrimps reach sexual maturity between four and eight weeks of age, when the individual is about six millimetres in length (1) (3) (6). Clutches of killer shrimp eggs can contain up to about 200 eggs (1) (5), but typically contain fewer than 50 (1) (3) (5).

It is estimated that the killer shrimp is able to expand its range by an average of 124 kilometres per year downstream, and 30 to 40 kilometres per year upstream (1). Its presence is reported to significantly alter the ecosystem in which the killer shrimp establishes itself (2).

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Killer shrimp range

The killer shrimp originates from the Ponto-Caspian region of Europe (1) (3) (4) (6), being found within the lower courses of large rivers within the Black and Caspian Sea basins, including in the Ukraine (1).

However, soon after its discovery this highly invasive species began to expand its range, both naturally and by transportation in ballast waters of boats (1), and had reached the Austro-German border by 1992 and the Rhine estuary by 1995 (1) (6). It has since spread rapidly in European water systems (6), and is now present and established in the UK (1) as well as 17 other European countries (4) including Germany, France, Italy, Switzerland and the Czech Republic (1) (3).

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Killer shrimp habitat

The killer shrimp is a freshwater species which can be found in a variety of habitats, including canals, rivers, lakes and reservoirs (1) (4), and appears to occupy the same habitats within its invasive range as it occupies in its native range (3). This species tends to prefer areas with hard banks and slow-flowing water (1), and demonstrates a preference for stretches of habitat with hard rocky bottoms or ledges (1) (3) (4), rather than bare sandy, muddy or fine gravel areas (1) (4).

Interestingly, although the killer shrimp is a freshwater species, it is capable of tolerating saline water, and so is able to colonise brackish coastal habitats (1). The killer shrimp is able to tolerate water temperatures up to about 23 degrees Celsius and salinity levels of up to 20 percent (6).

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Killer shrimp status

The killer shrimp has yet to be classified on the IUCN Red List.

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Killer shrimp threats

The widespread and abundant killer shrimp (6) is not currently known to be facing any threats, and is itself a threat to many other species outside of its native range, making it a major conservation problem (7). In just under 20 years, the killer shrimp has colonised most of continental Europe, and is now recognised as one of the region’s worst invasive species (7).

In the UK, the killer shrimp was first recorded in September 2010, in Grafham Water Reservoir, Cambridgeshire (1) (2), and has since become established (1). There are two further recorded infestations in the UK, both of which are in Wales (1). There are serious concerns about the continued spread of this destructive species, as the UK contains large areas of suitable canal, river and lake habitat in which the killer shrimp would thrive (1) (4). Further invasions, either in the UK or elsewhere, could have ecological or economic consequences (1) (6).

The killer shrimp is able to colonise new areas through a variety of different pathways. In addition to the killer shrimp being able to disperse downstream by natural drift (1), the recent expansion of European waterway networks and increases in shipping traffic are likely to facilitate this species’ invasion of new areas (1) (3) (4) (6) (7). This species has a high ability to remain attached to objects (7), such as scuba-diving and recreational boating equipment, and is also known to be carried in ballast water (1) (7).

The killer shrimp has several traits which make it a good invader, including its highly predatory behaviour, rapid growth, early maturation and high reproductive output (4) (6), as well as its ability to survive harsh transport conditions and being out of water for up to three and a half days (7). It threatens native species diversity through predation or competition (1) (3) (5), and in areas where the killer shrimp has established itself as an invasive species, it has placed pressure on local ecosystems, leading to the decline or even extirpation of native species (4) (7). The killer shrimp has been identified as a species which could affect the quality and distribution of fisheries, either through altering the environmental conditions or through carrying parasites which may negatively affect fish stocks (1).

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Killer shrimp conservation

The killer shrimp is not considered to be threatened, and as a result there are no known conservation measures in place for this species. However, as a highly invasive species with particularly destructive behaviour, it is vital to prevent the killer shrimp from spreading to new locations (2).

In the UK, a public education initiative known as ‘Check, Clean and Dry’ is being used to raise awareness of the simple prevention methods which can be applied to prevent the spread of invasive species, including the killer shrimp (7). These include checking equipment and clothing used in aquatic leisure activities, such as wetsuits (7), and disinfecting angling kit (2).

While chemical treatments have proved to be effective in exterminating the killer shrimp in laboratory conditions, the concentrations required for this are too high to be applied in the wild. However, simply dipping aquatic gear such as ropes and wetsuits in water of temperatures over 40 degrees Celsius for a short while has been shown to be an easy and effective way of ridding water sports equipment of live killer shrimps, therefore preventing the unwanted overland spread of this species (7).

To avoid the spread of the killer shrimp through boating activities, recommended management measures include inspecting and cleaning boats both before and after use, and draining bilge water from boats before leaving any given site (2). Alternatively, ballast water can be treated (3).

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Find out more

Find out more about the killer shrimp:

Find out more about other non-native species in the UK:

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Authentication

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

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Glossary

Algae
Simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.
Amphipods
A group of small shrimp-like crustaceans that includes sandhoppers, beach hoppers, and water lice.
Antennae
A pair of sensory structures on the head of invertebrates.
Brackish
Slightly salty water, usually a mixture of salt and freshwater, such as that found in estuaries.
Coprophagous
Feeding on dung, or faeces.
Larva
Immature stage in an animal’s lifecycle, after it hatches from an egg and before it changes into the adult form. Larvae are typically very different in appearance to adults; they are able to feed and move around but are usually unable to reproduce.
Mandibles
The pair of mouthparts most commonly used for seizing and cutting food, common to the centipedes, millipedes, insects and crustaceans.
Omnivorous
Feeding on both plants and animals.
Parasite
An organism that derives its food from, and lives in or on, another living organism at the host’s expense.
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References

  1. GB Non-native Species Secretariat (NNSS): Factsheet - Killer shrimp (September, 2013)
    https://secure.fera.defra.gov.uk/nonnativespecies/factsheet/factsheet.cfm?speciesId=1219
  2. GB Non-native Species Secretariat (NNSS): Invasive Species Alert: Killer shrimp (September, 2013)
    http://www.broads-authority.gov.uk/broads/live/managing/urgent-environmental-news/Dikerogammarus_villosus__v1%5B1%5D.2.pdf
  3. Delivering Alien Invasive Species Inventories for Europe (DAISIE) - Dikerogammarus villosus (September, 2013)
    http://www.europe-aliens.org/speciesFactsheet.do?speciesId=53301
  4. MacNeil, C., Boets, P., Lock, K. and Goethals, P.L.M. (2013) Potential effects of the invasive ‘killer shrimp’ (Dikerogammarus villosus) on macroinvertebrate assemblages and biomonitoring indices. Freshwater Biology, 58(1): 171-182. Available at:
    http://onlinelibrary.wiley.com/doi/10.1111/fwb.12048/pdf
  5. Gherardi, F. (Ed.) (2007) Biological Invaders in Inland Waters: Profiles, Distribution, and Threats. Springer, Berlin.
  6. Devin, S., Piscart, C., Beisel, J-N. and Moreteau, J-C. (2004) Life history traits of the invader Dikerogammarus villosus (Crustacea: Amphipoda) in the Moselle River, France. International Review of Hydrobiology, 89(1): 21-34.
  7. Bacela-Spychalska, K., Grabowski, M., Rewicz, T., Konopacka, A. and Wattier, R. (2013) The ‘killer shrimp’ Dikerogammarus villosus (Crustacea, Amphipoda) invading Alpine lakes: overland transport by recreational boats and scuba-diving gear as potential entry vectors? Aquatic Conservation: Marine and Freshwater Ecosystems, 23: 606-618.
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Image credit

Killer shrimp  
Killer shrimp

© The Environment Agency / via GBNNSS

GB Non-Native Species Secretariat
Non-native Species Secretariat
Food and Environment Research Agency
Sand Hutton
York
YO41 1LZ
United Kingdom
nnss@fera.gsi.gov.uk
http://www.nonnativespecies.org/

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