P. Fitzmaurice
Central Fisheries Board
Dublin, Ireland
ABSTRACT
Currently Ireland's freshwater fish fauna consists of 20 species. After the last glaciation period (about 15 000 B.C.) the fish fauna probably consisted of about eight species. Documentary evidence exists to show that at least seven species were introduced into Ireland within the last 400 years or so. Species which have established thriving populations include pike (Esox lucius), bream (Abramis brama), tench (Tinca tinca), roach (Rutilus rutilus) and dace (Leuciscus leuciscus). For climatic reasons carp (Cyprinus carpio), which has been introduced intermittently over the last 350 years, has not become fully established but remains a permanent member of our fish fauna through management policies. Rainbow trout (Salmo gairdneri) was introduced to Ireland in the early 1900s and although they have been stocked into approximatley 100 waters, only three isolated lakes have breeding stocks.
Of the introduced fish only three species could be said to have any adverse effects on existing fish populations. These species, namely, pike, roach and dace generate a considerable proportion of the £8 million, which Ireland earns as tourist revenue from coarse angling.
RESUME
La faune piscicole des eaux douces irlandaises se compose aujourd'hui de 20 espèces. Après la dernière période de glaciation (vers 17 000 avant J.C.), elle comprenait vraisemblablement huit espèces environ. On a la preuve que sept espèces au moins ont été introduites en Irlande au cours des 400 dernières années. Parmi les espèces qui ont prospéré, on citera le brochet (Esox lucius) la brème (Abramis brama), la tanche (Tinca tinca), le gardon (Rutilus rutilus) et la vandoise (Leuciscus leuciscus). Pour des raisons climatiques, la carpe (Cyprinus carpio), introduite par intermittence au cours des 350 dernières années n'est pas parvenue à s'établir complètement mais, grâce aux politiques d'aménagement, elle reste un membre permanent de la faune irlandaise. La truite arc-en-ciel (Salmo gairdneri) a été introduite en Irlande au début du siècle; environ 80 pièces d'eau ont été repeuplées mais seuls deux lacs isolés ont des stocks reproducteurs.
Trois seulement des espèces introduites ont eu des effets néfastes sur les populations existantes. Ces espèces, à savoir le brochet, le gardon et la vandoise, sont la source principale des huit millions de livres sterling que le tourisme rapporte à l'Irlande grâce à la pêche au poisson commun.
The freshwater fish fauna of Ireland consists of 20 species. It is probable that at the end of the last Ice Age, which occured about 15 000 B.C. (Varley, 1967), the indigenous fish species were anadromous. As the ice melted and retreated the fish moved northward after the ice. At that time, Ireland, Britain and the European land mass were joined. A number of fish species reached Britain whilst it was still connected to the continental land mass but before they had an opportunity to colonize Ireland, the land bridge with Britain had disappeared. Consequently, Ireland's freshwater fish fauna has less fish species diversity than that of Britain which, in turn, has less fish species than mainland Europe.
After the last Ice Age, Ireland's indigenous freshwater fish stocks probably consisted of: salmon (Salmo salar), sea trout and brown trout (Salmo trutta), char (Salvelinus alpinus), pollan (Coregonus albula), eel (Anguilla anguilla), Killarney shad (Alosa fallax killarnensis) and possibly two species of stickleback (Gasterosteus aculeatus and Pungitius pungitius).
It is more than likely that the other species which today complete the Irish freshwater fish list were introduced into Ireland after the twelfth century. In his translations of Giraldus Cambrensis' “Topography of Ireland”, O'Meara (1951) states that, “pike, perch, roach, gardon, gudgeon, minnow, loach, bullheads and verones” are absent. The distribution of some of these species and the inconsistency in which different combinations occur suggests that they were introduced. Documentation exists which shows that not only were certain species in the past restricted in their distribution but definite documentary evidence shows that Arctic char (Salvelinus alpinus), rainbow trout (Salmo gairdneri), tench (Tinca tinca), carp (Cyprinus carpio), roach (Rutilus rutilus) and dace (Leuciscus leuciscus) were introduced by named sources (Frost, 1940; Went, 1949, 1950; Piggins and Went, 1971 and MacCrimmon, 1971). Historical documents indicate that pike (Esox lucius) must have been introduced (Went, 1957) and there has been only one recorded capture of a single specimen of catfish (Ictalurus melas) by Fitzmaurice (1977). It is also more than likely that bream (Abramis brama) and rudd (Scardinius erythrophthalmus) are introduced species but there is no documentation to indicate their dates of introduction.
The results of known introductions and their current status are shown in Fig. 1.
In 1969 the Salmon Research Trust of Ireland received what was purported to be a consignment of Icelandic sea trout (Salmo trutta). 135 000 eyed ova were retained for rearing. By September 1970 it was noticed that the fish were, in fact, Arctic char (Piggins and Went, 1971).
Over half the original consignment was stocked out as fed fry in mid 1970 (Salmon Research Trust of Ireland Inc., 1971). Subsequently only three recaptures were made from this stocking. No recaptures were recorded from the 4 277 Arctic char stocked in 1971 as 1+. The species did not become established.
30 000 ova were sent to the Crumlin River in west Galway for hatching and subsequent release. None of the resultant planting were ever encountered.
Rainbow trout were originally introduced into Ireland from the United States in 1899, 1900 and 1901 (Ravenal, 1899, 1900 and 1901). It was intended to use them for stocking sport fisheries locally (Worthington, 1941) but this venture was a failure. About 1905–7, Lough Shure on Aran Island off the coast of Donegal was successfully stocked (Frost, 1940) and a breeding population persists to the present. No further introduction appeared to have taken place into Ireland until 1955, when rainbow trout eggs were imported from a trout farm situated in Surrey, England. This importation formed the core of a breeding stock. The resultant offspring were used for commercial rearing and for stocking sport fisheries.
Approximately 100 different lakes and ponds have already been stocked with rainbow trout. Self-maintaining populations have been established in only three known locations, the above mentioned Lough Shure, Lough na Leibe in County Sligo and White Lake in County Westmeath.
Went (1957) states that after fairly complete searches of records and historical literature, he was unable to discover any references to pike in Ireland before the sixteenth century. Indeed literature referring to the twelfth century was notable in that it specially mentions the absence of pike. There is no name for pike in the Old Irish language. The modern name (Farran, 1946) is “Gaill iasc” which literally translated means “foreign fish”. This indicates that the species is an introduced one. By the late sixteenth century pike appear to have been well established in the southern part of Ireland (Longfield, 1929; Johnson, 1810). In the late seventeenth century pike were absent from the west of Ireland (O'Flaherty, 1846) but by the early nineteenth century they were well established and had colonized the Corrib and Moy catchments (Maxwell, 1832). The species has appeared in the upper reaches of the River Bandon within the past decade.
At present, pike are found in all the river systems draining the central plain of Ireland. It is absent from water systems of the extreme northwest, west and southwest. It is also absent from coastal mountain areas of the southeast. Pike is the only piscivorous fish to be found in Irish fresh waters.
Catfish is an introduced species on the European mainland (Blanc et al., 1971). The species is commonly used by aquarium hobbyists. During a stock assessment operation, a single specimen was captured in a gillnet in the Lough, Cork. There is no evidence to suggest that the species became established. It was almost certainly dumped in the lake by a local aquarium enthusiast.
Details of the introductions of dace and roach into the Cork Blackwater River are well known and documented. Evidence of the introductions, by one of the people directly involved, was given at an inquiry held in 1940. A visiting pike angler from England brought two tins of mixed dace and roach for use as bait in 1889. Whilst angling he left the two tins of bait tied by cords to a wall. The cans were swept away by a flood and about two years later the fish were noticed in the river. Since that date they have spread throughout the whole of the Blackwater system. At present dace are found only in the Cork Blackwater River system.
In about 1905 roach were transferred to an artificial lake in County Tyrone in Northern Ireland and following a severe flood they escaped into the River Mourne, a tributary of the River Foyle. In the sixties roach were identified for the first time in the River Erne and within a decade had completely colonized the catchment area. By 1980, the species had been recorded from Shannon, Boyne, Dee, Liffey and Corrib catchments (Fitzmaurice, 1981).
The rapid spread of roach may be attributed to sport anglers using the fish as live bait for pike. Anglers also deliberately transferred roach in the hope of improving sport angling.
Introductions of tench and carp into Ireland date back as far as the seventeenth century. Rutty (1772) noted that tench and carp were said to have been brought into Ireland for the first time during the reign of James I, 1603–25. Went (1950) refers to proposed introductions by Richard Boyle, the Great Earl of Cork, in 1634 and 1640. Tighe (1802), Daniel (1807), Windele (1849) and Thompson (1856) all mention locations in which tench and carp were supposed to have been stocked or were present at the time of writing. Although tench are to be found in some of the waters mentioned by these authors, carp have long since disappeared.
The present distribution of tench and carp in Ireland can be considered in two parts - pre-1950 stocks and stockings since 1950.
In the early fifties, tench were distributed in the River Shannon catchment and its associated lakes. It was also found to be sporadically distributed in the midlands and south of the country, mainly in small lakes and ponds. Since 1956, tench have been introduced into approximately 80 different waters, mostly small lakes, in the hope of creating sport fisheries. Wherever tench were stocked, breeding populations were established.
Prior to 1950, information on carp stocks is rather vague and fragmentary. However, around 1950 it appears that the distribution of carp in Ireland was limited to a few small shallow ponds in the southern part of the country. Known locations included a private quarry pond in a Dublin suburb. The quarry was subsequently filled in with rubble. Small ponds at Blackwater, County Wexford, and at Kilsheelan, County Tipperary, contained breeding stocks of stunted fish. In 1976 both ponds dried up with consequent loss of breeding stock. A small lake near Clonmel, County Tipperary, contains a breeding stock and the largest carp captured in Ireland (14.64 kg) was recorded from this lake in 1977.
Since 1950, 32 ponds or lakes have been stocked with carp for sport angling purposes. All these stockings, with the exception of two plantings, were made from endemic stocks. In 1951 some two-year olds were imported from Germany and stocked into Ballinderry Lake, County Westmeath. In 1974, despite a governmental ban on the importation of live fish into Ireland, approximately 40 small carp were brought in from England and stocked into a small pond near Ballina, County Mayo.
Legislation in Ireland prohibits the importation of live fish for sport or commercial purposes. Introductions are only allowed if the Ministry for Fisheries is fully satisfied that no damage can be done to endemic fish stocks.
Rainbow trout were stocked alone or in combination with brown trout into lakes which previously held no fish or held coarse fish, which were removed with rotenone. Some lakes which held small populations of brown trout were also stocked. All rainbow trout used in stockings were an autumn spawning shasta strain. However, in the three naturalized populations the fish have reverted to spring spawning.
Under Irish conditions it has been found that rainbow trout are unlikely to establish breeding populations in competition with brown trout. In sport fisheries, overwintering survival of plantings is poor. Plantings of 1+ and 2+ fish now take place. Present management policy for rainbow trout sport fisheries is to limit plantings to a few small selected lakes where the species is unable to spawn. The sport fisheries are maintained by annual stockings. In Lough na Leibe and White Lake, because of limited spawning, stocks are maintained by supplemental plantings.
There are some isolated reports of rainbow trout escapees from freshwater fish farms spawning in rivers but there is no evidence to suggest that self-maintaining populations have become established. There have also been a few reports of escapees from marine cage culture locations running into rivers but no known spawnings have taken place.
The introduction of pike and its subsequent spread to a large proportion of the country has had an adverse effect on the indigenous salmonid populations. In waters where brown trout, cyprinids and perch are abundant, pike prey on brown trout in preference to other fish species (Healy, 1956). Toner (1959) showed that in Lake Corrib, a large trout angling water, pike stomachs contained brown trout in percentages ranging from 51–66.6 percent, the calculated weight ratio of trout to other fish eaten was 4.2:1. Salmon smolts are particularly vulnerable to predation during migrations.
In waters being developed as trout fisheries, pike stocks have to be controlled by gill-netting, trapping and local application of rotenone on known spawning areas.
Pike fisheries are a valuable asset as a tourist income earner. At present, Ireland earns £4–6 million in external revenue from pike angling.
The presence of dace and roach in the Cork Blackwater River have affected salmonid production and have caused the decline of brown trout fishing. Both species have colonized areas where brown trout and salmon parr were abundant in the past. They compete for food and the ecology of the dace being such that it can penetrate further up the faster-flowing regimes successfully displacing brown trout and salmon parr.
Despite legislation banning fish transfers within Ireland, roach have been introduced to numerous lakes and rivers over the last 20 years. Although roach are a valuable asset as a sport fish, they have an adverse effect on the endemic species present. Within a few years of introduction into a river system, they become the dominant species. They displace brown trout and rudd stocks disappear almost to the point of extinction (Fitzmaurice, 1981). Fertile hybrids between roach, bream and rudd are produced and with back crossing, roach become the dominant species.
Tench and carp are solely used for sport angling purposes. Both species are at the northern limit of their geographical distribution. In waters where tench are stocked, the naturalized populations reproduce readily although Ireland's climate is such that in summers which are much cooler than average, spawnings may fail to take place. This happens in rivers and large lakes where spawning temperatures are not realized. However, in small shallow sheltered ponds spawnings are likely to occur every year. Growth rates are good, spawnings are adequate and it is only in small ponds that overpopulation and stunting is likely to occur.
Tench stockings have proved beneficial for sport angling. They do not appear to have any adverse effect on existing fish populations. They are usually stocked in waters which have either bream or an absence of bottom feeding fish.
Self-maintaining populations of carp are difficult to obtain in Ireland due to climatic reasons. In only two known locations have annual spawnings taken place. The ponds concerned have a temperature of 4–5°C above national average but in 1976 under drought conditions these ponds dried out with consequent loss of spawning stock. In exceptionally warm summers there is likely to be spawnings in most areas where the species are stocked.
Ecological problems, with carp such as those experienced in the U.S.A. (Stroud, 1975) are never likely to happen in Ireland. Indeed the main problem with carp in Ireland is trying to prevent the species from dying out.
The introduction of Arctic char and catfish have both been failures.
Overall, the introductions of fish species into Ireland have been beneficial as far as sport angling is concerned. The external tourism earning for freshwater angling in 1981 was approximately £18 million.
The introduction of rainbow trout, tench and carp have been particularly beneficial in adding to species diversity, enhancing commercial production and sport fishing. With pike, dace and roach, their introduction has been beneficial to a certain extent but their impact on the ecology and their interactions with endemic species has made them undesirable. Roach are probably the least desirable of the introductions.
Blanc, M. et al., 1971 European inland water fish: a multilingual catalogue. Poissons des eaux continentales d'Europe: catalogue multilingue. Peces de aguas continentales de Europa: catalogo multilingue. Binnengewasser Fische Europas: Mehroprachiger Katalog. London, Fishing News Books for FAO, pag.var.
Daniel, W.B., 1807 Rural sports. London, ii. p. 215
Farran, G.P., 1946 Local Irish names of fishes. Ir.Nat.J., 8:344–7, 370–6, 420–8, 430–3
Fitzmaurice, P., 1977 The Cladocera of Ireland and their importance in the diet of fishes. Ph.D. Thesis, National University of Ireland
Fitzmaurice, P., 1981 The spread of roach (Rutilus rutilus L.) in Irish waters. In Proceedings of the Second British Freshwater Fisheries Conference. Liverpool, University of Liverpool, pp. 154–61
Frost, W.E., 1940 Rainbows in acid water: a note on the trout of a peat lough on Arranmore. Salm.Trout Mag., (100): 234–40
Healy, A., 1956 Roach and dace in the Cork Blackwater. J.Dep.Agric.Fish.Dubl., 53:67–73
Johnson, S., 1810 The works of the English poets. London, iii, 413
Longfield, A.K., 1929 Anglo-Irish trade in the sixteenth century. London, p. 49
MacCrimmon, H.R., 1971 World distribution of rainbow trout Salmo gairdneri. J.Fish.Res.Board Can., 28(5): 663–704
Maxwell, W.H., 1832 Wild sports of the west. London, vol. 1:114–6
O'Flaherty, R., 1846 A chronographical description of West or hIar Connaught. Dublin, edited by J. Hardiman, p. II
O'Meara, J., 1951 The first version of the topography of islands, by Giraldus Cambrensis; a translation. Dundalk, p. 18
Piggins, D.J. and A.E.J. Went, 1971 Introduction of Arctic char (Salvelinus alpinus) into Irish waters. Ir.Nat.J., 17:144
Ravenel, W. de C., 1899 Report on the propagation and distribution of food-fishes, 1897–99 - steelhead and rainbow trout. Rep.U.S.Comm.Fish Fish., 25:
Ravenel, W. de C., 1900 Report on the propagation and distribution of food-fishes, 1899–1900 - steelhead and rainbow trout. Rep.U.S.Comm.Fish Fish., 26:100–5
Ravenel, W. de C., 1901 Report on the propagation and distribution of food-fishes, 1900–1901 - steelhead and rainbow trout. Rep.U.S.Comm.Fish Fish., 27:88–92
Rutty, J., 1772 The natural history of County Dublin. Dublin, vol. 1:364–5
Salmon Research Trust of Ireland Inc., 1971 Annual report of the Salmon Research Trust of Ireland Incorporated. Annu.Rep.Salm.Res.Trust Irel.Inc., (16):11–2
Stroud, R.H., 1975 The introduction of exotic fish species into waters of the United States. In Proceedings of the Seventh British Coarse Fish Conference. Liverpool, University of Liverpool, pp. 3–13
Thompson, W., 1856 Natural history of Ireland. London, vol. 4:135 p.
Tighe, W., 1802 Statistical observations relative to the County of Kilkenny. Dublin, p. 156
Toner, E.D., 1957 Pike in trout waters. Salm.Trout Mag., 5:104–10
Varley, M.E., 1967 British freshwater fishes. Factors affecting their distribution. London, Fishing News (Books) Ltd., 148 p.
Went, A.E.J., 1949 Giraldus Cambrensis notes on Irish fish. Ir.Nat.J., 9:221–4
Went, A.E.J., 1950 Notes on the introduction of some freshwater fish into Ireland. J.Dep.Agricult.Fish., Dubl., 47:3–8
Went, A.E.J., 1957 The pike in Ireland. Ir.Nat.J., 12:177–82
Windele, J., 1849 Historical and descriptive notices of the city of Cork and its vicinity. Cork, p. 370
Worthington, C.B., 1941 Rainbows. A report on attempts to acclimatize rainbow trout in Britain. Salm.Trout Mag., (100):241–60; (101):62–99
Fig. 1 Current distribution and status of fish species known to have been introduced into Ireland
