Some Irish Fish Species

The brook lamprey lives exclusively in freshwater. Occurs in middle and upper reaches of small streams and rivers; occasionally in lakes. Larvae lie buried in the substrate while adults live in the open water. The larvae are filter feeders, non-feeding adults. Reproduction takes place upstream, from April to May.

The lamprey has a bad reputation in Ireland. Infamous as the ugliest fish in our waters, the lamprey lacks true bone and jaws. It has a large sucker instead of a mouth and survives by attaching itself to other fish such as salmon or herring and digesting their body juices. It is not a wholly destructive relationship however. The lamprey and salmon spawn in the same gravel beds. By spawning earlier, the lamprey de-silts and prepares the beds for the salmon, presumably improving aeration and, therefore, egg incubation.

Prefers cold, well-oxygenated upland waters although their tolerance limits are lower than those of rainbow trout. Favors large streams in the mountainous areas with adequate cover in the form of submerged rocks, undercut banks, and overhanging vegetation. Mainly diurnal. Feeds on aquatic and terrestial insects, molluscs, crustaceans and small fish. Matures in 3-4 years. Reproduces in the rivers. Life history and spawning behaviour is similar to salmon. Female produces about 10,000 eggs.

In Ireland char are not very well understood as little research has been carried out. Initially the char was thought to be quite rare as it was an infrequent component of anglers catches. However, in Ireland the distribution of char was always quite widespread, particularly in western counties, though it may become rare if the present rate of extinction continues. Most of the populations of char in Ireland feature diminutive fish, however they are not a true dwarf race as their size is not dictated solely by genetics. Irish char are small compared to anadromous char, but their size range is typical of other European landlocked populations. It is thought that char in Lough Owel may have reached weights of up to 1.4kg, but this may never be known as this population is now extinct.

Young remain in freshwater for 1-6 years, then migrate to the ocean and remain there for 1-4 years before returning to freshwater to spawn. Return to the sea after spawning. Active during the day. Juveniles feed on mollusks, crustaceans, insects, and fish; adults at sea feed on squids, shrimps, and fish. Adults in freshwater which are approaching the reproductive stage do not feed. Growth in freswhwater is slow while in the sea is very rapid. Life history of the salmon can be read from the growth zones in the scales. Several lake populations are landlocked. Prefers cool temperature.

Midwater species, rarely far from shore, primarily anadromous in the west and lacustrine in the east; shoaling at least during spawning season. Feeds on shrimps and small crustaceans; larger individuals may feed on small fish. Migratory form enters the rivers and spawns in March - May on sandy or gravely bottoms. Produces 8,000 - 50,000 yellow eggs with a diameter of 0.6-0.9mm which adhere to the bottom. Hatch in 3-5 weeks. They become sexually mature in 3-4 years (15-18cm) in brackish populations, 1-2 years (8-10cm) in freshwater. Smells like cucumber.