Fish play an important part in freshwater habitats in Northern Ireland and contribute a great deal to our economy. Angling is a very enjoyable pastime for a lot of people both in rivers and on lakes. Commercial fishing also is locally important and includes freshwater inland fisheries for eel and pollan on Lough Neagh.
Only 11 freshwater fish species are considered native to Northern Ireland, although a number of coarse fish species have been introduced. This is a very small number compared with the rest of the UK and Europe. However, some of these species are of considerable biodiversity significance due to their genetic distinctiveness.
The fish species pollan, for example, has not been genetically altered since the ice age and the largest population in Europe is found within our very own Lough Neagh and Lower Lough Erne.
In general, fish communities within our larger nutrient rich lakes and rivers are a mix of coarse and salmonid species, but today there are few truly natural stocks due to breeding with introduced species. Lough Melvin supports the Northern Ireland priority species Arctic charr at its only known site in Northern Ireland. Other Northern Ireland species of conservation concern in Lough Melvin are three distinct races of brown trout and the Atlantic salmon
Invertebrates are multi-cellular animals without a backbone. They are the most diverse species group and are critical in the functioning of ecosystems, often using freshwater at some stage in their lifecycle. Freshwater habitats have a rich variety and include insects, crustaceans, spiders, numerous types of worms and snails.
Northern Ireland fens are particularly important for invertebrates, several of which are absent or threatened in Great Britain. These include dragonflies (such as the Irish damselfly), beetles (for example the whirligig beetle and the water beetle) and butterflies and moths (such as the marsh fritillary butterfly).
In addition, there are a number of species associated with our rivers that are of particular conservation importance. For example, there are concentrations of remaining populations of the rare freshwater pearl mussel and white-clawed crayfish.
The freshwater crayfish is commonly found in alkaline streams, rivers and small lakes where the levels of calcium carbonate are high, relying on this chemical to build up its exoskeleton. These conditions are often provided in marl lakes and therefore these may support large populations of this species. Snails, such as the marsh snail, can persist during periods of drought under stones and in damp vegetation and are common in turloughs (a unique type of disappearing lake found mostly in limestone areas).
Reptiles and amphibians
There is only one native terrestrial reptile in Northern Ireland, the viviparous lizard, which is widely distributed, particularly in heaths, bogs and sand dunes, but little information is recorded.
The smooth newt is the only native amphibian and is found in fens and in many small water bodies such as ponds. Ponds, in particular, provide amphibians with a freshwater habitat in which to spawn during the spring. The common frog is a very widespread species in Ireland but is thought to be introduced.
The frog populations here are considered to be important both for species conservation in Europe and because they play an important part in food chains.
Bird species can be found breeding in a wide variety of locations throughout Northern Ireland and a number of these live in freshwater habitats or visit them to drink and feed.
Some lakes support internationally important bird populations. Lough Neagh and Lough Beg, in particular, hold up to 80,000 wintering waterfowl of some 20 species, including ducks, geese, swans and gulls.
The presence of particular birds can be a good sign of a healthy habitat. Reedbeds are of value to a range of specialist bird species that depend on them for their survival, such as the reed bunting, the water rail, the sedge warbler and the reed warbler, so their presence is encouraging.
Like all animals, mammals need freshwater to survive and hence may visit rivers, lakes and streams at some time to drink. Some, however, live in close proximity to water-bodies and although our species are limited in comparison to the rest of the UK, there are some that you may come across.
The otter is the fourth largest land mammal in Northern Ireland. It occurs frequently along many of the river systems, although it is seldom seen and will avoid contact with humans.
The American mink first escaped from fur farms and began to establish itself in Ireland during the 1950s. It is relatively common and is found along rivers, streams, lakes and canals.
Within freshwater environments plants play a variety of different roles, from helping oxygenate the water to providing homes for insects. To survive aquatic plants can have quite different adaptations from those on land. They may float on the waters surface (from microscopic phytoplankton to water lilies), be partially submerged (such as common reeds) or totally submerged (for example, a variety of pond weeds).
Mosses and liverworts are found throughout freshwater bodies. They differ from flowering plants in having modified stems (rhizoids) instead of roots and reproduce by means of spores.
A common algae in our freshwaters are stoneworts, so called because they are often incrusted with calcium carbonate. Twenty species of stoneworts have been recorded in Northern Ireland.
You don’t need to visit the Amazon to discover animal eating plants! The greater bladderwort supplements a low nutrient diet by consuming insects and small fish and can be found in Lower Lough Erne and peat bogs.