Invasive aquatic plants
Some of the most worrying species of invasives in Ireland are aquatic plants. In many cases the plant fills an empty niche and then expands rapidly and competes for additional niches. Oftentimes the native species are ousted and the ecology of the waterway can be changed dramatically. This can lead to waterways becoming completely choked by a single species impeding navigation, angling and other recreation.
Invasive aquatic animals
As most of the fish in Ireland were introduced by man throughout the history of the country many fish species could be regarded as invasive. Those which are well established are considered to be naturalised species having reached some sort of equilibrium in the environment.
Those fish which are still considered invasive species due to their recent arival or continued spread through our water courses are:
In more recent times we have had new invertebrate species released into Irish waterways. These include Zebra Mussel and Bloody Red Shrimp.
Zebra Mussels have colonised many waterways and causing significant ecological and economic impacts.
Bloody Red Shrimp has been confirmed in Lough Ree on the Shannon River system. Crangonyx pseudogracilis is another freshwater shrimp which is colonising Irish water courses. Now Asian clam and killer shrimp threaten our waterways.