grafham water (credit: jane belinda smith)
The winter months are moving behind us and there’s a definite feel of spring in the air. As we start to go about our outdoor activities again it’s worth remembering that in October 2010 an invasive species alert was issued over a freshwater shrimp.
Notifiable invasive species arrived in UK last winter.
If your spring and summer activities involves spending time in and around freshwater then it’s well worth getting to know the identification marks of the Dikerogammarus villosus shrimp. It’s a notifiable species and if you spot one then you need to report it to the authorities – the details and extra information are given at the bottom of this post.
The species is notifiable for a reason – it can have devastating impacts on a freshwater ecosystem such as a lake if it gets a foothold. Where D. villosus have colonised systems on mainland Europe it has changed the make-up of those systems. Not only will this shrimp out-compete our native freshwater shrimps but it will also predate on very young fish. It’s ferocious capacity to prey on such a wide range of species has earned it it’s common name of ‘killer shrimp’ or ‘pink peril’.
Dikerogammarus villosus currently restricted to three sites in UK.
Fortunately the shrimp is currently limited to very few sites in the UK;
- Grafham Water SSSI in Cambridgeshire – discovered on 3rd September 2010,
- Cardiff Bay – discovered on 25th November 2010,
- Eglwys Nunydd in Port Talbot – discovered on 26th November 2010.
There are a number of bio-security measures in place at these locations that water users such as anglers and boat operators need to undertake to ensure that the shrimps do not escape from the area and expand into other water bodies. These measures include:
- clean and air drying equipment including boats and launching trailers,
- emptying ballast before leaving the water body,
- disinfecting angling gear before reuse,
- not taking any lake water with you when you leave – including any used to mix up bait.
Containment is currently the only viable management prospect for this species.
Future impacts of the killer shrimp.
This will be the first spring and breeding season for the D. villosus shrimp in the UK. The females are most productive during April and May. How successful was the shrimp at surviving our recent cold weather and how successful will it be at breeding in the UK environment? These are questions which will be answered over the coming months.
The invasive species originated in the river basins of the Black and Caspian Seas before extending their range in 1992 once the Danube-Maine-Rhine Canal opened. Further expansion into Western Europe occurred through ballast water transfer. The shrimp is causing problems across Europe and have been listed as one of the worst 100 invasive species currently affecting Europe.
The shrimps are idea colonisers – female shrimps can lay up-to 190 eggs three times a year. This high level of fecundity means that new populations are easily established. Studies on the colonisation of the River Rhine by D. villosus has shown that it can colonise downstream at a rate of 124 km per year and colonise upstream sections at a rate of 30-40km per year.
The shrimps also seems to prefer freshwater and brackish environments with hard banks and substrates – this makes the canal system of the UK an ideal environment for the shrimps to spread across the country if they manage to evade the containment systems currently in place. With much of the UK’s river systems interconnected and with free movement of pleasure craft across much of the water system the shrimps have the potential to cause real problems.
