Two more non-native species have been listed among a handful of potentially harmful flora and fauna to watch out for in Norfolk this spring.
American mink and killer shrimp are two of the most recent animals to have been listed by the Norfolk Non-native Species Initiative as invasive and harmful.
Warnings of other non-native species to Norfolk have included Chinese mitten crabs, signal crayfish, and Japanese knotweed.
American Mink
American mink were introduced to the UK for fur farming in the 1920s and have since established large numbers in the wild due to escapes and deliberate releases.
Roughly the size of a ferret, these animals can reach up to 60cm in length and weigh between 1-2kg, with male minks generally larger than females.
They most commonly have dark brown or black fur with a white patch under the chin and are found in wetland environments such as rivers and lakes.
Their territories along a riverway usually range up to five kilometres but they have been known to travel more than 80km in search of good quality habitat and mates.
READ MORE: Warning issued after Chinese Mitten Crabs spotted in Norfolk
The American mink has caused over 90pc decline in native water vole populations since their introduction and have a devastating effect on local wildlife due to their predatory adaptability.
They are also known to hunt ground-nesting birds like kingfishers and poultry, fish and eels.
The Norfolk Mink Project is a dedicated group tasked with the control and eradication of American mink, established in 2003 to help stop the decline in water vole populations.
The NNNSI advises all mink sightings should be reported to the Norfolk Mink Project's website as soon as possible since the animals can cover vast distances daily.
Killer Shrimp
The killer shrimp is a crustacean that is native to eastern Europe and was first recorded in the UK in 2010.
This first sighting was at Grafham Water in Cambridgeshire and since then they have been identified at various sites across England and southern Wales including multiple confirmed sightings in east Norfolk.
The shrimp can grow up to 30mm in length and has large mandibles that make it a very effective predator.
Their diet includes native aquatic invertebrates, fish and their eggs, and insect larvae.
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This species can breed rapidly - reaching sexual maturity at four to eight weeks - with each female capable of producing up to 50 eggs at a time.
They can breed at any time of the year in still and slow-flowing fresh water so long as it is above 13C and can survive in water with very low oxygen levels such as where there is a lot of algae.
The shrimp can spread to new locations easily on angling, boating and other leisure craft and people are advised to clean their equipment when moving between water bodies to prevent their spread.
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If you think you have found a killer shrimp, photograph it as clearly as possible and send it to the Norfolk Non-native Species Initiative with the location.
This is very important as once the shrimp gets established in a water body it is almost impossible to control.
The news comes shortly after a warning was issued by ecological organisations after Chinese Mitten Crabs were reported to have been seen in the Buckenham and Oby areas, which an NNNSI spokesman said could be "really bad news".
If you have concerns about any of the species named in this list or any other, please get in touch with the Norfolk Non-native Species Initiative at NNNSI@norfolk.gov.uk.
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