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    Help protect our wildlife from these tiny invaders! They may look harmless but they can cause big problems if left to their own devices!

    1. Killer Shrimp

    Environment Agency

    Killer by name and killer by nature. These diminutive shrimps, which grow to just 30mm and hail from from rivers in eastern Europe and western Russia, are actually voracious predators that gobble up everything in sight from our native shrimp to a wide range of other native pond and river invertebrates, and can disrupt the delicate balance of life in water ways. They can survive over two weeks out of water as long as they remain damp. Could you be carrying this killer on your water sports clothing or equipment?

    2. American Bullfrog

    Gabriel Michelin

    These frogs can grow to well over twice the size of our common frogs and can cause serious damage. They have earned the reputation as one of the most harmful species that can reach foreign shores. Not only do they eat a wide range of prey (including snakes!) for lunch, but they also carry a disease which has led to worldwide amphibian decline and to several global extinctions … pretty deadly for a frog! They have been kept as pets, but if they escape they can be deadly!

    3. Signal Crayfish

    GB Non-native Species Secretariat

    The signal crayfish, which looks similar to a mini-lobster (average size 6-9cm) and comes from the US, is driving the native white-clawed crayfish towards extinction and causing declines in the diversity and richness of water communities. Commercial fisheries have been affected because they eat fish eggs and compete with native fish for places offering protection. They can strip rivers and streams of all other life, until they have to resort to cannibalism to survive! Burrowing by crayfish can cause erosion of riverbanks and destabilise structures built at the edges of rivers.

    4. Asian Hornet

    Jean Hexaire

    Asian Hornets are smaller than our native hornets, with distinctive yellow feet and dark abdomen. These ferocious flying insects prey primarily on honeybees, but also eat a wider range of other insects. They have evolved to ‘hawk’ outside honeybee nests waiting to catch returning bees. They have not been sighted in the UK but we are asking people to remain vigilant!

    5. Quagga Mussel

    David Aldridge, Cambridge University

    This little mussel from eastern Europe is only the size of a thumbnail but, boy, can it cause some problems. The quagga mussel has an amazing filtering capacity and ability to produce dense populations. As a result, it can significantly reduce native biodiversity, and alter the balance of life in freshwater systems. It can also become a very expensive nuisance when growing in pipes of water treatment plants or commercial ships.

    6. Carpet Sea Squirt

    GB Non-native Species Secretariat / Via

    With a name like sea squirt, it’s hard to see why these seemingly inoffensive little water dwellers from the Pacific Ocean are on the list. But these little 1mm long creatures have a habit of clubbing together in huge colonies (of up to several square kilometres!) which overgrow native species don’t leave much real estate left for anything else! They can also clog up fishing equipment, boats and smother reefs.

    7. Topmouth Gudgeon

    Matt Brazier, Environment Agency

    The name gives this small fry away. This guzzling mouth, originally from eastern Asia, has a penchant for eating young fish and eggs, breeds fast and spreads disease – it is a 2-7.5cm parasite that attacks other fish. All in all, other fish don’t have a hope when the gudgeons come to town.

    8. Harlequin Ladybird

    Nick Davies / Via

    These little ladybirds certainly keep you on your toes, coming in three colour forms – from yellow-orange to red with 0 to 21 black spots, to black with two red spots, to black with four red spots – you never quite know what you’re going to get. They are replacing our native ladybirds, out-competing them for food and in some cases even eating them! They also have an unwelcome habit of setting up residence in buildings in huge numbers.

    9. Floating Pennywort

    GB Non-native Species Secretariat / Via

    This prolific plant, which is native to South America, grows at such a phenomenal rate that it stops the growth of other aquatic plants, blocks movements of animals and boats, preventing travel and leisure activities on waterways. It can grow up to 20cms a day on a sunny summer day and is spreading through numerous waterways in the UK.

    10. Citrus Longhorn Beetle

    The Food and Environment Research Agency

    These flamboyant looking beetles (2-4cm) hail from Asia and pose a serious threat to orchards, forestry and native trees in Britain. They lay their eggs in the tree, which develop into wood boring larvae that burrow further into the wood to feed. This weakens trees making them vulnerable to diseases and wind damage.

    11. Slipper Limpet

    GB Non-native Species Secretariat

    This unusual 2-5cm limpet which looks a bit like a gnarly old toenail preys on shellfish, can smother seabed species and alter seabed habitat structure dramatically. It competes for food and space with other filter-feeding species including native mussels and oysters. It also has a habit of clinging on to important farmed shell species and man-made structures and equipment

    12. Chinese Mitten Crab

    Stephan Gollasch / Via The Food and Environment Research Agency

    Don’t be fooled by the harmless sounding name because these east Asian crustaceans are voracious predators that will consume a range of invertebrate species and fish eggs, reducing their numbers and affecting the normal balance of natural life. They grow to between 3-10cm and will also burrow into river banks, increasing erosion and river clarity, and causing banks to collapse.

    You can help stop the spread of these critters by reporting your sightings to iRecord … and when using waterways, make sure you Check, Clean and Dry water equipment and clothing worn to stop them spreading into new waters! Find out more at

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