Specially designed baited traps and new methods have been trialled by Environment Agency Wales to improve detection of an invasive shrimp which was found at two places in Wales last November.
Initial results show that the new traps are more effective at detecting the shrimp than the current sampling methods.
The aim is to deploy the new traps to check for the shrimp at other high priority sites across Wales. Sites are classified as 'high priority' because they offer the perfect invasive shrimp habitat (lots of hard surfaces like boulders, rocks and gravel just below water), are used for water-sports, or are important conservation areas.
Two types of trap have been trialled. The first are traps adapted from ones used to catch the non-native American signal crayfish; the other is a 'drop net' designed for catching larger shrimps and prawns. Both traps are being baited with cat food.
In tandem with the Welsh trials, officers are awaiting delivery of 40 new traps that have been successfully trialled in Grafham Water in Cambridgeshire to help with the shrimp sampling work in Wales.
So far, the shrimp has been found in Wales at Cardiff Bay and at Eglwys Nunydd Reservoir in Port Talbot.
The only other confirmed location in the UK is at Grafham Water found in September last year. It is not yet known how the species arrived at the two south Wales sites or at Grafham.
The invasive shrimp, measuring some 30mm in length, originated from the region around the Black Sea and the Caspian Sea. It is believed to have spread across Western Europe via waterways such as the Danube / Rhine Canal.
It has already colonised parts of Western Europe, killing and out competing a range of aquatic species such as freshwater invertebrates, particularly native freshwater shrimps and even very young fish, thereby potentially altering the ecology of the habitats it invades.
The Welsh Assembly Government and Defra have established a national Task Group to tackle the shrimp in England and Wales, that includes Environment Agency Wales and the Countryside Council for Wales.
The national Task Group urges that anyone who uses waters where the shrimp are present to take steps to prevent the species from spreading. Simple things like cleaning and drying equipment thoroughly after use and checking equipment when leaving the water are vital.
At the south Wales sites Cardiff Harbour Authority and Tata Steel - Eglwys Nunydd’s owners - are working closely with the Environment Agency Wales and groups representing anglers and other recreational water users on bio-security measures to contain the spread of this species.
Chris Mills, Director, Environment Agency Wales said:
“These new traps will mean help us to monitor other high-priority sites across Wales. The shrimp’s breeding season starts in the spring so now is a crucial time for this work.
“As well as sampling and monitoring sites across Wales, we are helping the national Task Group and site owners instigate actions to deal with the shrimp. The national Group is also commissioning new research to improve the limited knowledge available about the shrimp and what we can do in the UK to control it.
“As the national action programme develops, the most important thing is to contain the shrimp. We ask that people who use Cardiff Bay and Eglwys Nunydd follow the Task Group’s advice to help tackle this unwelcome guest.”
Councillor Nigel Howell, Executive Member for Sport, Leisure and Culture said:
“The invasive shrimp was discovered in Cardiff Bay as a result of the robust environmental monitoring programme put in place by Cardiff Harbour Authority. Strict bio-security measures have been in place for several years, since Zebra Mussels were found in 2004.
“I am pleased that the cross agency partnership has been established and is already making Bay users aware of what they need to do to prevent this species being spread elsewhere.”
Since discovering the presence of the shrimp, the Harbour Authority has continued their close working relationship with Cardiff University to determine the extent of the spread.
Cardiff University study
The extent of Cardiff Bay’s invasive shrimp population was recently assessed by a Cardiff University Zoology student, Caroline Rees during work for her undergraduate dissertation. The Cardiff University team’s investigation work was supported by Cardiff Harbour Authority.
While studying another invasive species, the zebra mussel, Caroline found Dikerogammarus distributed across large areas of the 200 hectare Bay at densities sometimes greater than 4,000 per square metre.
Professor Steve Ormerod of the University’s School of Biosciences, said:
“The shrimp population must have developed very rapidly over the last one to two years because we did not find it during very extensive surveys of zebra mussels during 2006-2009. It appears to be taking advantage of the Bay’s rocky shoreline and large aggregations of zebra mussel, which is also an invader. The shrimps are using the zebra mussel beds as habitat and we’re investigating the possibility that they’re feeding on their waste.
“The stringent bio-security measures already in place for Zebra Mussels in the Bay should help with the battle to contain the invasive shrimp as well. Zebra mussels now number many millions in Cardiff Bay, and in the summer a single litre of water can contain 10-15 of their larvae which emphasises the need to follow the Task Group’s national advice to try and prevent these invasives spreading to other lakes. However, European research shows just how rapidly these species move between locations, hence the need for expanded monitoring here in Wales ”