Watch out for stowaways

Every water user could be inadvertently carrying unwanted passengers! The lakes, canals, rivers and reservoirs of Wales are at risk of becoming home to a number of unwanted species accidently spread by water users. The arrival of these non-native species can have a huge impact on Welsh freshwater species and cause nuisance, damage and even injury to water users.

Here are three of the least wanted:

Zebra Mussels: The zebra mussel Dreissena polymorpha is a bivalve that lives in fresh or slightly brackish (salty) waters. It has brownish-yellowish triangular shells (up to 50 mm) with dark and light coloured (“zebra”) zigzag banding. It forms large colonies on the lake bed and can cover hard structures such as jetty pylons, buoy chains and boat hulls. It can form colonies with thousands of individuals which have covered and damaged inflows, outflows, propellers, steering gear and other kit. Within the United States, it has caused many millions of dollars of damage. The sharp shell edges have been known to cause nasty injuries to water users.

http://www.europe-aliens.org/pdf/Dreissena_polymorpha.pdf

Killer Shrimp: This freshwater shrimp is similar to our native freshwater shrimps but can grow much bigger (to 30mm) and is a voracious predator of pretty much anything, hence its rather dramatic common name. It has spread across much of mainland Europe where its presence upsets natural food chains and native populations of freshwater species including fish.

http://www.europe-aliens.org/pdf/Dikerogammarus_villosus.pdf

Asiatic Clam: The Asiatic clam is a bivalve with a tan to brown, ridged globular shell. They can occur in large numbers in sediments and are usually <3cm in size. Individuals are both male and female and they are self fertilising, so a single clam can develop into a significant population. As with the killer shrimp, the presence of Asiatic clams upsets the natural food chains within water bodies, impacting on the populations of native species including fish.

http://www.europe-aliens.org/pdf/Corbicula_fluminea.pdf

All three of these species are present in South Wales and perhaps elsewhere within the UK. The larval stage of each species is tiny (<1mm) and can survive in any damp kit or tiny amounts of trapped water. When kit like boats, bait buckets, wetsuits, life vests and boat trailers are used on different sites, there is a risk of accidently bringing in these unwanted species. The presence of these species directly harms wildlife, anglers and recreational water users.

However, following a few simple precautions can significantly reduce the risk of contaminating water bodies with these species. Cardiff Bay is home to zebra mussels and there is information from the Harbour Authority on cleaning at: http://www.cardiffharbour.com/content.asp?nav=3,43,115&parent_directory_id=1&id=134&d1p1=1

Follow these simple steps before travelling between water bodies with sailing, angling, canoeing or any wet kit.

Check - for any information on non-native species at water recreation sites and follow the instructions

CLEAN – remove any plants, animals, mud and muck from any gear that has been in contact with water, including boat trailers and vehicles which are often overlooked.

DRAIN – all water from bilges, ballast tanks or anywhere water can collect and flush with dilute bleach solution waiting for 1 hour before draining and rinsing – ensure this process occurs well away from any watercourses.

DRY – allow all kit to dry thoroughly, in well ventilated and sunlit places – if this is not possible, sponge down with dilute bleach solution, ensuring that washings do not enter watercourses.

Following these simple steps will go a long way to prevent the spread of these species. With the help of responsible water users, we can keep the water bodies of the Brecon Beacons free of unwanted visitors.