• Eel Research 1965-1971

      Moriarty, C (Department of Agriculture and Fisheries (Fisheries Division), 1972)
      The catch of eels for the Republic of Ireland is very low. It averages 125 tons a year, thus comparing unfavourably with such figures as 800 tons for Northern Ireland and 1,500 tons for Holland. Since 1965 experiments have been in progress to find out whether there is any possibility of increasing the production of this valuable fish. A detailed report of the investigations was completed in March 1972 and this leaflet gives a summary of the most important conclusions. The approach to the problem was to make a study of some aspects of the life of the eel, concentrating on lakes where commercial eel fishing was well established. In addition to this some fishing trials were made in the estuaries of rivers such as the Munster Blackwater and the Shannon where no large-scale eel fishing had ever taken place.
    • Eel Research 1972

      Moriarty, C (Department of Agriculture and Fisheries (Fisheries Division), 1973)
      The national survey of eel stocks was continued in 1972. For the first time the eel population of a river, the Munster Blackwater, was studied. It proved to be the most densely stocked freshwater area sampled to date. It was calculated that between five and ten tons of eels must leave the river each year on migration. Unfortunately the eels were slow-growing and of rather low quality. The eel stocks of Lough Gill and Lough Conn were found t o be poor, heavily overfished and the eels were slow-growing. Two restricted areas which had been subjected to intense commercial fishing for several years, the South Sloblands Channel in County Wexford and the Broadmeadow Estuary, showed poor stocks and will take several years to recover, Unfortunately, eels grow so very slowly (rarely taking less than ten years to reach market size) that their stocks are highly susceptible to damage from overfishing.
    • Eel research 1973

      Moriarty, C (Department of Agriculture and Fisheries (Fisheries Division), 1974)
      Eel research broke new ground in 1973 by beginning a study of elvers and young eels. Elvers enter fresh water in spring and make their ways upriver. Precise information on when they arrive, in what numbers and how far they travel is very limited, although the subject was studied in the early years of the present century. Knowledge of the behaviour of eels in these early stages is essential because we have now proved that the scarcity of eels in many Irish waters is caused by the failure of the small eels to reach them. The situation could be improved by artificial transport of the young eels but first they must be caught and we must find out where and how best to catch them. In 1973 the arrival of elvers happened rather late and many were still on the move from the end of June right up to August. A study of the young eels at Parteen Weir on the River Shannon showed that there were virtually no elvers amongst them. This indicated that elvers took more than a year to travel distance of nine miles to Parteen from the top of the tide.
    • Eel Research 1978-1979

      Moriarty, C (Department of Agriculture and Fisheries (Fisheries Division), 1980)
      The good prices paid to fishermen for eels have led to an increased interest in eel capture in Ireland. In that regard the results of stock assessments examined in conjunction with records obtained from other European eel fisheries, have indicated that the present national catch could be increased by at least 100% and perhaps by several times as much. Such an improvement could be effected by the overland transport of elvers from collection points near the coast. An operation of this kind in already in progress on the Shannon river system undertaken by the Electricity Supply Board who own the entire fishery. Sampling of eels within that system have indicated that substantial increases in the numbers of growing eels in the lakes and in the numbers of male silver eels captured, have taken place. Since it takes between ten and twenty years from the beginning of a stocking programme for any results to be apparent it is essential to devise a system for making an accurate assessment of the developments. This is the principal aim of the routine sampling of yellow eels which forms the greater part of current research work.
    • Eel Research in 1968

      Moriarty, C (Department of Agriculture and Fisheries (Fisheries Division), 1969)
      Fyke nets for the capture of eels have been in use in some parts of the country since 1961. These are “summer” type nets, laid on the bottom in lakes and river estuaries and having, when set, a maximum height of about 60 cm (2 ft.). Experiments with these nets were made in a number of lakes from July to September. Five students were employed to operate the nets and examine the eels. Each student was supplied with a set of eight nets (sixteen traps with eight leaders arranged in a line) and the nets were fished daily except at weekends or in rough weather. The traps were 1.84 m (6 ft.) long with an opening diameter of 43 cm (16 ins.), the leaders were 4.7 m (18 ft.) long and the mesh size at the cod end was 1 cm (0.4 ins). The areas chosen were Lough Corrib (mainly in the vicinity of the Docros peninsula), Loughs Inchiquin and George, near Corofin, Co. Clare, Loughs Ecnish and Tullyguide, near Killeshandra and Town Lake, Dromore Lake and Dromloona Lake, near Cootehill, Co. Cavan, the latter three by kind permission of Brigadier Dorman O'Gowan. In all cases the lengths of the eels were measured and the stomachs and otoliths of as many as possible were collected. The Lough Corrib eels were also weighed, their weights were used subsequently to calculate the weights of the eels from the other lakes. Examination of the stomach contents and otoliths of the eels has not yet been completed. The indications are that the majority of the eels feed on invertebrates while a small proportion feed on fish. Loughs Corrib and George in the areas fished offer poor feeding while Inchiquin and the County Cavan lakes are rich.
    • Eel Research in 1969

      Moriarty, C (Department of Agriculture and Fisheries (Fisheries Division), 1970)
      Most of the research effort was concentrated on experiments with summer fyke nets on the lines of the 1968 work (leaflet No. 9). Three zoology students, Messrs. Dermot Douglas, Tommy Hayden and Martin O’Grady were employed on bursaries for the field work and the Electricity Supply Board co-operated on the Shannon System. The standard set of eight nets (sixteen traps with eight leaders, arranged in line) was used on the Corrib system. On account of losses and damage to nets only seven were available for the Shannon but it is unlikely that this made any material difference to the results. When possible fishing took place daily. The figures are based, with one exception, on the total number of days when the nets were fishing, including weekends and stormy weather when they were not lifted daily. The exception was Lough Mask where persistent rough weather made lifting the net impossible for a fortnight. It was found in this case that the smaller eels escaped and the catch was therefore not typical of normal conditions. The nets used had a mesh size at the cod end of 10 mm.
    • Eel Research in 1970

      Moriarty, C (Department of Agriculture and Fisheries (Fisheries Division), 1971)
      The summer of 1970 was the third in which a standard set of fyke nets was used to make a detailed study of the eel stocks in a particular lake. The lake chosen was Lough Key which lies on the Boyle River, a tributary near the source of the River Shannon. Miss Ann Fortune and Miss Christine Royle, zoology students, were employed on bursaries for the field and some of the laboratory work. The method of working has been described in previous Leaflets (Nos. 9 and 21). In brief it consists of fishing daily with a standard set of eight nets (sixteen traps with eight leaders arranged in line) which have a cod-end mesh size of 10 mm. The eels were measured, weighed and sexed and otoliths and stomachs were preserved for examination.
    • Eel research in 1974

      Moriarty, C (Department of Agriculture and Fisheries (Fisheries Division), 1975)
      The value of eels at present is about 50p per pound, placing them amongst the most highly priced fish. Our studies over the past few years have shown that most of the Irish eel-barfing waters are seriously under stocked. This situation can be greatly improved by artificial stocking.
    • Eel Research in 1975

      Moriarty, C (Department of Agriculture and Fisheries (Fisheries Division), 1976)
      The national survey of Irish eel stocks was completed in 1975. A definitive report is being prepared and will be published later. The work began eleven years ago and the final phase was a study of the eels in the River Barrow. We have now searched for eels in coastal locations, in river estuaries, rich lakes, poor lakes, mountain streams and lowland rivers rich and poor. This has provided a picture of how and where quantities of eels may be found, how they may best be fished for and managed and how the stocks may be improved for the benefit of the fishermen. The stocks are definitely low, although the annual output of eels is of the order of one hundred tons with a value of over £100,000. About two-thirds of this catch came from the Shannon fishery. In general, fishing is intensive and the scope for improvement in fishing methods is limited. Stocking with elvers however, can greatly increase the catch in the long term and at a value of £1,000 a ton it is clearly worthwhile to go to work on this. The Electricity Supply Board has in fact been engaged in restocking for many years and can expect an increased yield in the near future.
    • The Eel Stocks of the Shannon System and Prospects for Development of the Fishery

      Moriarty, C (Department of the Marine, 1987)
      Lough Neagh has long been known to yield the greatest quantities of eels of any water body in Ireland, the annual catch being in excess of 700 tonnes. The Shannon catchment on the other hand yields less than 100 tonnes per annum. This Leaflet describes work carried out in Lough Neagh and in the Shannon catchment in 1985 and 1986 which has indicated that eels are now more abundant in the Shannon System than in Lough Neagh. The implications are that the stocks in the Shannon System are sufficient to yield an annual catch of as much as 1,000 tonnes and value £2 million. The current capital cost of establishing a two-man crew capable of catching 3 tonnes of eel, value £6,000, is £2,500. Annual running costs per crew are less than £1,000. The large scale exploitation of the fishery would involve much more substantial investment by the owners. Arising from this paper, the Department has raised the matter with the ESB and the Shannon Regional Fisheries Board to agree on a strategy to maximise employment from the fishery.
    • Fish Kills in Ireland 1991-1992

      Moriarty, C (Department of the Marine, 1993)
      The numbers of fish kills were below the average for the ten years since the systematic recording of incidents began in 1983. Totals were 60 and 51 for 1991 and 1992 respectively. Both years therefore represent a continuation of the downward trend which began after the peak of 122 incidents in 1987. An important factor in the improved situation was the reduction in the number of silage discharges which had been the most serious problem for a number of years. Untreated sewage and industrial effluents in general have also shown downward trends. . Two serious problems remaining are 'enrichment' and run-off from farmyards, which includes spillage of slurry. Slurry and farm effluents in fact showed an increase in 1992 over 1991. Enrichment by excessive phosphorous, derived both from partially treated domestic sewage and from fertiliser, causes algal blooms leading to deoxygenation of the water and the death sometimes of very large numbers of fish - to say nothing of environmental conditions which are unacceptable to everybody who uses rivers or lakes. The effect of a discharge of effluent depends on many factors. In wet weather with high stream flows the damage will be minimised because the effluent is diluted quickly. A spillage beside a small river will led to a much more extensive fish kill than the same quantity of effluent will cause in a large one. These and other factors probably explain why, in spite of the small number of fish kills in 1992, nearly twice as much river was affected as in 1991.
    • Fish Kills in Ireland in 1988

      McCarthy, D; Moriarty, C (Department of the Marine, 1989)
      The number of fish kills reported in 1988 showed a very welcome reduction to 50 incidents after the 1987 record of 122. The principal source of trouble has continued to be inadequately planned agricultural practices. Run-off from silage was once more the most serious problem, accounting for 13 kills. Slurry or manure accounted for seven more. While weather conditions may have alleviated the problem, due credit for the improvement must be given to the farmers who responded to the campaign organised by the Government in conjunction with the farming organisations. Industrial sources were responsible for 11 incidents. They have been increasing since 1985 but still remain below the maximum recorded in 1984. Sewage, for the first time since 1980, was not implicated. The most serious events in 1988 were on the Inny caused by an industrial effluent and on the Dodder following a discharge of silt from a water treatment plant.
    • Fish Kills in Ireland in 1989

      Moriarty, C (Department of the Marine, 1990)
      The final estimate for the number of fish kills in 1989 was 111. The increase in 1989 is largely accounted for by the exceptional warm weather conditions which prevailed. Details of all the incidents are given in the following pages. When these are analysed some very significant facts emerge. The number of fish kills while higher than in 1988 (50 kills) was about nine percent lower than in 1987 (122 kills). Low water due to dry weather conditions was the most important factor in 1989 raising the number of kills by 50%. Despite weather conditions, fish kills due to agricultural causes showed little change on the 1988 level - thus maintaining the substantial reduction in kills due to these causes achieved in 1988. As many as 50 of the incidents resulted from pollution which in a normal wet summer would not have caused such serious damage. These problems give a useful, if painful, reminder that water pollution can have devastating results. They also serve to highlight high risk situations. Many of the 1989 fish kills resulted from a shortage of oxygen from untraceable causes, for example from excessive plant growth due to fertiliser run-off or domestic sewage - or both. Others came from identifiable sources. In about half these cases the authorities felt that genuine accidents had happened and a warning to the guilty party was all that was needed. In others, twenty-seven in all, legal proceedings were set in motion.
    • Fish Kills in Ireland in 1990

      Moriarty, C (Department of the Marine, 1991-07)
      The total of 52 fish kills in 1990 was a marked improvement over the previous year when 111 were reported. Although this result was no better than that for 1988, it represented a considerable achievement because 1988 experienced a wet summer with high water flows while 1990 was exceptionally dry. Because of the poor dilution of pollutants, low river flows are usually associated with an increase in the number of fish kills. All three traditional causes of fish kills, agriculture, industry and sewage showed a downward trend. These have all been subjected to a campaign of information and enforcement of the regulations. This has brought about an increased awareness of the hazards and major improvements have been made in reducing the risks of accidental spillages. In spite of these efforts, the problem remains very serious. Although so much better than the peak figures of more than 100 fish kills in a single year, the level of 50 is unacceptably high. The analysis of the year's results shows that agricultural sources continue to cause extremely serious damage. The problem lies partly in the fact that a single accidental discharge into a salmonid nursery river can kill many thousands of fish for as much as 20 kilometres downstream. If the downward trend of problems from agriculture and industry can be maintained, the greatest threat in water pollution is likely to be that of enrichment, above all the release of excessive phosphate into the environment. Two sources, fertilizer and domestic sewage, are implicated. The sewage element can be controlled by upgrading treatment plants wherever necessary. The reduction of phosphate runoff requires continued attention to the information campaign for farmers to explain the: need for extreme care in fertilizer application. Remedial action in this case increases farm profits since all the fertilizer which pollutes the rivers is lost to the land.
    • Fish Kills in Ireland in 1993

      Moriarty, C (Department of the Marine, 1994)
      The pattern of fish kills in 1993 showed a dramatic change from that of the previous ten years. The number of incidents showed a very welcome reduction to a total of 33, the lowest since systematic records began to be kept in 1982. Only one case of damage caused by silage effluent was reported and two from farm effluents - in the recent past these were the most frequent and serious sources. However, fish kills provisionally attributed to 'enrichment' attained a record total of 16, most of them in the lakes in Co. Cavan in the Erne catchment. Sewage and runoff from agricultural land are the main sources of the phosphorous which brings about excessive blooms of microscopic algae. Enrichment has caused extremely serious problems in the past, in particular in Loughs Ennel and Sheelin. In both cases, remedial measures were successful, although problems have arisen again in the case of Lough Sheelin. The more widespread problem in the Erne catchment may be more difficult to contain and there are also signs of trouble in the Rivers Shannon and Lee. The trend of increasing numbers of enrichment-based fish kills does not necessarily mean that even more such incidents will take place in 1994 - but it is virtually certain that similar problems to those of 1993 will arise sooner or later unless action is taken.
    • Fish Kills in Ireland in 1994 and 1995

      Moriarty, C (Marine Institute, 1996-05)
      In 1994, the downward trend in numbers of fish kills continued, the total for the year being 32. However, in 1995 a long spell of dry weather greatly reduced the flow in rivers in all parts of Ireland and the number of fish kills rose to 84, the highest since 1989. In 1994, farmyard effluents, silage and slurry together accounted for one third of the fish kills. Industrial effluents and enrichment both caused 19% of the total. Storm water runoff and cement spillage in building operations were the other identified causes. In 1995, enrichment was the most frequent problem, followed by agriculture. Inadequately treated sewage was implicated in five cases and waterworks effluent in two. In 17 cases the mortalities were associated with reduced water flows or high temperatures or a combination of the two. The dry summer in a number of cases revealed unsatisfactory levels of pollution which are usually masked by higher water flows such as occurred in 1994. The increase in farm-based problems suggested that some of the improved facilities for storage and treatment of farm waste which were made in the late 1980s may now be due for maintenance. Enrichment of lake systems, particularly those of the Erne and Shannon, has now established itself as the most serious threat to the condition of natural waters. Fish kills are an early warning of a situation which may develop and have far-reaching effects on economic interests far removed from the fishery itself.
    • Freshwater Crayfish 1968

      Moriarty, C (Department of Agriculture and Fisheries (Fisheries Division), 1969)
      The freshwater crayfish inhabits some rivers and lakes in Ireland. The only species known to inhabit Ireland is Astacus palipes. It looks like a lobster but is very much smaller, seldom more than 10 cm (4 ins.) in length. As a rule it hides by day and comes out to hunt at dusk. Apart from the fact that it feeds on various kinds of dead animal matter nothing is known about its feeding habits in Ireland. In other parts of Europe it eats water weed and many kinds of small creatures. The crayfish can be caught easily in special traps which resemble small lobster pots and are baited with raw meat. Boiled crayfish are excellent food but are rarely eaten in Ireland. In other countries, especially Sweden, they are regarded as luxury items and are sold at high prices. Crayfish caught in Ireland for export to Sweden should be worth about 5/- per pound to fishermen.
    • The Impact of Eel Fyke Netting on Other Fisheries

      Moriarty, C (Department of Tourism, Fisheries and Forestry, 1986)
      The small fyke net was introduced to Ireland in 1963 and has been operated extensively in tidal water ever since. Experiments in freshwater began in Lough Corrib in 1967, conducted by the then Department of Agriculture and Fisheries. In 1970 operation by professional fishermen under special authorisations began. It has been effectively demonstrated by the Department's experiments, by information furnished by the professional fishermen and by observations by local fishermen and the Department's officials that fyke nets could be used for eel fishing without harmful effects on other fish stocks. As a result, the fyke net was listed as a "scheduled engine" in the Fisheries Act, 1980
    • Prospects for the development of the Irish eel fishery

      Moriarty, C (Department of Fisheries and Forestry (Trade and Information Section), 1981)
      It is considered that the lakes and rivers of Ireland (Republic) could be managed to achieve a production of 1,500 tonnes of eel a year. The value of this catch would be £3 million for fresh fish. A fishery with this yield could form a basis for a processing industry and enhanced value. Experience indicates that the current catch, of not more than 150 tonnes per year, does not provide a sufficiently regular supply of fresh eels to maintain a processing operation and consequently the eels are sold only to wholesalers. The poor catch results from inadequate stocks rather than from inefficient methods of capture. This leaflet gives a description of the eel fishery and its progress in recent years and explains how the stocks can be increased for the future. The special attraction of the proposal is that it offers a means of making a tenfold increase in the yield of one of the most highly priced species of fish without posing any threat to the ultimate survival of the species. The method to be used is the transfer to good feeding grounds of elvers which would otherwise die within months of arrival on our coasts.
    • Zebra Mussels in Ireland

      Minchin, D; Moriarty, C (Marine Institute, 1998-02)
      The zebra mussel was reported for the first time in Ireland during 1997. It may have been introduced during or before, 1994. Information, based on eye-witness accounts from 1995 and the age structure of zebra mussels sampled during October and November 1997, suggests they first became established in the region between southern Lough Derg and Limerick Docks. The species expanded its range during 1996 to include most of Lough Derg and by 1997 had settled in the remaining north-eastern region of the lake. The mussels could have reached Ireland in several ways. The most likely vectors are boats carried on trailers directly from Britain, and one recently imported barge carrying live mussels was found. There may have been a number of introductions. It is possible that some arrived in ballast water from shipping in Limerick Docks. Mussels foul a wide range of structures and easily settle on firm surfaces, including water supply pipes. For this reason their presence is of serious concern to amenity and industry. In the Shannon they have formed dense concentrations on the dock gates in Limerick and the sluice gates and pillars of the Parteen and Ardnacrusha dams. Piped water to a hatchery was blocked with a subsequent loss of fish. Densities on the hulls of vessels were up to 53,000 per sq.m. They were most frequently found attached to the hulls of barges and private craft not slipped annually. Few hire cruisers were fouled. Some mooring have sunk under the weight of attached mussels. Fresh-water mussels Anodonta anatina, rocks, stones and some aquatic plants were found with attached zebra mussels. It is likely there will be changes to the ecosystem. The overall effects cannot be predicted and will require careful monitoring. It is inevitable that mussels will spread throughout the navigable waterways of the Shannon and Erne and to the Barrow via the Grand Canal. The spread to other waterbodies can be curtailed if boats are cleaned before being transported. Because mussels can survive up to three weeks under damp and dull conditions special care is necessary to ensure that transfers are avoided. Leaflets have been distributed to boat owners and anglers to advise on precautionary measures.