Water Technology (3rd edition)
Chapter 3. Factors Determining the Distribution of
Animals and Plants in Freshwaters
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3.1.2 Alien or exotics species

Asian Clam invades Irish Freshwaters

Reports in late summer of 2010 have  shown that the aquatic invasive species Asian Clam (Corbicula fluminea), which was recorded for the first time in Ireland in April 2010 in
the River Barrow in County Carlow, is more widespread than previously thought. The mollusc has also been recorded in Lough Corrib and the Grand Canal.  Canals are
trans-catchment waterways that have significantly accelerated the spread of invasive species in other countries.
More details

The clam originally comes from south-eastern Asia and grows very rapidly reaching high densities in a short period of time.  Like the Zebra mussel (Dreissena polymorpha) it
significantly damages the food web and excludes the native mussel species.  In the US the mussel is estimated to cause in excess of a $1 billion of damage each year.
3.1.2 Alien or exotics species

Killer Shrimp (Dikerogammarus villosus) found in British Isles

The predatory shrimp Dikerogammarus villosus, which preys on a wide range of macro-invertebrates and even small fish has been
recorded in the British Isles for the first time. It is extremely aggressive and dominates habitats by killing and maiming unselectively. It comes
from the Steppe region between the Black Sea and the Caspian Sea. This environment has made it extremely versatile being able to thrive in
habitats subjected to wide fluctuations in temperature, salinity and dissolved oxygen. The shrimp is much larger (up to 30mm) than the
native shrimps such as Gammarus and has obvious strips making it easy to identify.  The shrimp, described by the Environment Agency as
'particularly vicious and destructive'  was discovered by anglers in Grafham Water, a large reservoir in Cambridgeshire. It has been moving
through Western Europe over the past two decades mainly via the key European waterways the Rivers Danube, Rhine, Elbe and Rhone, but
it was a shock when it turned up in the UK in late September 2010.  A containment strategy has been put into place with the water leaving the
reservoir passing thorough a double set of coarse and fine mesh, although it is inevitable that the species will escape into the adjacent River
Ouse.  All boat movements are being closely monitored.  The Environment Agency have moved very quickly to control this invader and it will
be interesting if the strategy succeeds.  
The predatory shrimp
Dikerogammarus villosus