• Aspects of the limnology of Lough Gur, Co. Limerick

      King, J .J.; O'Grady, M .F. (Department of Agriculture and Fisheries [Fisheries Division], 1994)
      A survey of Lough Gur, a 76 ha lowland lake in Co, Limerick, was carried out between December 1988 and October 1989. The lake is a hardwater, eutrophic system with consistently elevated levels of total phosphorus. Large algal crops were produced in spring, dominated by the diatom Asterionella formosa Hass. and in the autumn, dominated by Chlamydomonas - type biflagellates. A large crop of the floating macrophyte, Ceratophyllum demersum L., persisted throughout the year. Asellus and Chironomid larvae were the principal invertbrates recorded. The fish stock was dominated by rudd, Scardinius erythrophthalmus L. In addition pike, Esox lucius L. and eel, Anguilla anguilla (L.) were encountered.
    • A Comparitive Limnological Study of Two Irish Lakes (Lough Sillan, Co. Cavan and Lough Dan, Co. Wicklow).

      O'Connor, J. P.; Bracken, J .J. (Department of Agriculture and Fisheries [Fisheries Division], 1978)
      A comparative study of Lough Sillan (Co. Cavan) and Lough Dan (Co. Wicklow) revealed that these two Irish lakes differ markedly in their physicoRchemical and faunal characteristics. The possible causes of these observed dissimilarities are reviewed and discussed. Lough Sillan may be classified as moderately eutrophic while Lough Dan is both humic and oligotrophic.
    • The Crayfish Astacus pallipes of an Irish Lake

      Moriarty, C. (Department of Agriculture and Fisheries [Fisheries Division], 1971)
      The population of a 30 hectare limestone lake was studied. The crayfish were most active from July to September. Females carrying eggs were present from November to June. Parameters describing the measurements of the stock available for trapping were determined.
    • The Currane, Co. Kerry, Sea Trout Fishery, 1980-1986

      Fahy, E.; Rudd, R. (Department of Agriculture and Fisheries [Fisheries Division], 1988)
      An updated account of the unique Waterville sea trout stock is provided. The latest genetic work is reviewed and the vulnerability of these fish to introgression by other strains of trout is considered. Waterville sea trout are relatively long lived and the consequences of this fact are documented with data supplied by anglers over a period of six years. On average, Waterville sea trout are the largest in Ireland although bag sizes in the fishery are small. Alterations in the stock are monitored over seven years from 1980 using angler caught material. Back-calculations of lengths at various ages are supplied together with information on weight: length relationships. condition factors and sex ratios. The main influence on the age structure of the stock was the recruitment of post-smolt annually. Freshwater productivity could be explained by the influence of length of growing season but regulating factors in the saline environment were not identified. There was some agreement between indicators of recruitment in the Waterville and Burrishoole (Co. Mayo) fisheries. The relationship between B type increment - a crucial element of growth bringing parr to migratory dimensions - and growing season is investigated and various methods of expressing the B increment in quantitative terms are examined.
    • The Distribution of Irish Char (Salvelinus Alpinus)

      Went, A. E. J. (Department of Agriculture and Fisheries [Fisheries Division], 1971)
      Char* (Salvelinus alpinus) are rare in most places in Ireland to-day but they were formerly more widespread and abundant. About twenty-five years ago the Fisheries Division of the Department of Agriculture and Fisheries started to offer rewards for char submitted for examination and this has had the result of providing specimens which would otherwise have been lost. Many of these specimens wcre taken on rod and line but in recent years considerable numbers have been obtained in connection with either the improvement schemes of the Inland Fisheries Trust, Inc. or investigations concerned with the effects of drainage operations on Lough Conn.
    • The Distribution of the crayfish Austropotamobius pallipes (Lereboullet) in Ireland

      Lucey, J.; McGarrigle, M. L. (Department of Agriculture and Fisheries [Fisheries Division], 1987)
      The distribution of Austropotamobius pallipes, the only freshwater crayfish recorded from Ireland and presumed to be an old native, is described using some 300 records collected since 1976: the positive and negative loci from regularly sampled rivers and streams are used to provide a baseline from which any future changes in distribution can be monitored. Although absent from some regions, most notably the south-west (south of the Dingle-Dungarvan line) and north-west (County Donegal), crayfish are widely spread in the country principally in Carboniferous Limestone areas. The natural chemistry characteristics of the river and stream sites supporting crayfish had the following ranges: pH 7.2 - 8.4, alkalinity 34 - 356 mg/l and hardness 47 - 402 mg/l. Factors which might be important in influencing distribution of A. pallipes in Ireland, including pollution, predation and disease, are discussed.
    • The Early Life of Brown Trout (Salmo Trutta L.)

      Kennedy, M.; Fitzmaurice, P. (Department of Agriculture and Fisheries [Fisheries Division], 1968)
      The programme of research included field and laboratory studies of certain aspects of the early life history of the trout that are considered below.
    • Ecological Changes over 21 Years Caused by Drainage of a salmonid stream, the Trimblestown River

      O'Grady, M. F. (Department of Agriculture and Fisheries [Fisheries Division], 1991)
      A site on the Trimblestown River (Boyne Catchment) studied by McCarthy (1977 and 1983), pre- and post-drainage (1968 to 1974), was re-examined by the author in 1989. Changes in the nature of the stream bed, in-stream and bank flora and fish stocks over the entire period (1968 to 1989) are reviewed. Data indicate a general ecological recovery of the site 17 years after drainage works.
    • Ecological Changes over 30 Years caused by drainage of a salmonid stream, the Bunree River

      O'Grady, M. F.; King, J. J. (Department of Agriculture and Fisheries [Fisheries Division], 1992)
      The general ecology of two sites in the Bunree River, May catchment are described for 1990 and compared with the observations of Toner, O'Riordan and Twomey, (1965) at the same sites 30 years ago when parts of this catchment were subjected to arterial drainage. Differences observed are discussed with particular reference to salmonid populations.
    • The Ecology of Brown Trout and Juvenile Salmon in the River Owena, Co. Donegal

      McCarthy, D .T. (Department of Agriculture and Fisheries [Fisheries Division], 1972)
      The growth rate and population structure of brown trout and juvenile salmon in two oligotrophic nursery streams in County Donegal in the North west of Ireland are compared, as well as data on sex ratios and sexual maturity. Details of the food of brown trout and salmon and the smolt run in 1967 are discussed. Estimates of fish population density and biomass for these rivers have been made and related to estimates made in two other rivers of similar terrain, one oligotrophic and the other eutrophic. Pre-migratory mortality rates in the salmon populations are discussed.
    • The Effects of Drainage on the Trimblestown River

      McCarthy, D. T. (Department of Agriculture and Fisheries [Fisheries Division], 1977)
      The effects of arterial drainage on the macro-invertebrates and flora of a salmon nursery stream are described. A section of the Trimblestown River, Co. Meath was sampled from 1968 to 1974. In drainage operations of this kind the substratum where insect life predominates is removed, also fish and salmonid ova and fry life is affected by mechanical disturbance. A Surber stream-bottom sampler covering an area of 1 square ft (O.093m2) was used to take 107 samples. Wet and dry weights of the fauna were determined. A survey of the aquatic flora, pre- and post-drainage is also described. The fauna and flora were seriously depleted after drainage but recovered rapidly both in numbers and biomass a year after drainage was completed. There was an increase in the growth of emergent vegetation after drainage. Filamentous algae and Chara sp. recolonised the bed of the river replacing two submerged species (Fontinalis sp and Rorippa nasturtium) which had been abundant prior to drainage.
    • Feeding Relationships of trout salmo trutta L., Perch Perca fluviatilis L., and Roach Rutilus rutilus (L.) in Lough Sheelin, Ireland

      Gargan, P. G.; O'Grady, M. F. (Department of Agriculture and Fisheries [Fisheries Division], 1992)
      Samples of trout, perch and roach were collected by gill netting from eight sampling stations over the period February 1982 - March 1984 to assess competition for food between the three species. At each of the sampling stations quantitative collections of benthic invertebrates were taken in order to examine the relationship between feeding and food availibility. Results indicate a significant correlation in diet between trout and perch, little correlation in diet between trout and roach and moderate correlation between perch and roach. The most important competitive interaction between all three fish species is likely to be at their juvenile stage for a cladoceran diet.
    • Feeding relationships of trout Salmo trutta perch Perca fluviatilis L and roach Rutilus rutilus L in Lough Sheelin Ireland.

      Gargan, P. G.; O'Grady, M. F. (Marine Institute, 1992)
      Samples of trout, perch and roach were collected by gill netting from eight sampling stations over the period February 1982 - March 1984 to assess competition for food between the three species. At each of the sampling stations quantitative collections of benthic invertebrates were taken in order to examine the relationship between feeding and food availibility.
    • Feeding, Growth, and Parasites of Trout Salmo Trutta L. From Mulroy Bay, an Irish Sea Lough

      Fahy, E. (Department of Agriculture and Fisheries [Fisheries Division], 1985)
      The feeding and gut parasite burden of 354 trout collected between May 1980 and April 1981 from Mulroy Bay on the north coast of Ireland are described and compared with a collection of trout from the Irish Sea. The sea ages of the fish ranged between 0 and 2 sea winters, more than 90% being post-smalt. Males and females were equally represented in the younger, females predominated in the older. The food web was larger than in the Irish Sea, insects and crustaceans being its most numerous constituents but fish making up the greatest volume. Shoal fishes were relatively unimportant. Parasites comprised five species of Digenea, one cestode and a nematode. All occurred at a relatively low incidence and burden. Weights of the Mulroy fish were lower than for trout of equivalent length from the Irish Sea.
    • Fluctuations in the Characteristics in Irish Salmon

      Went, A. E .J.; Twomey, E. (Department of Agriculture and Fisheries [Fisheries Division], 1971)
      Fluctuations in the catches and stocks of fish are exceedingly important and have interested scientific workers for years. As far as the salmon is concerned it is known that great fluctuations occur not only in the number of fish entering the rivers from year to year but also in their character. This paper is an attempt to put on record certain changes, some of which have already been recorded in papers on Irish salmon published in a very wide range of journals.
    • Insect Emergence Data from Four Small Lakes in the South and Southwest of Ireland

      Bracken, J. J.; Murray, D A. (Department of Agriculture and Fisheries [Fisheries Division], 1973)
      Emerging insects from four small lakes in Counties Cork and Kerry were captured using floating Mundie emergence traps during the period from late April to early November 1969. The data obtained are examined to provide information on distribution, emergence periods and seasonal fluctuations in numbers of insects present. The traps were serviced at weekly intervals and the weekly maximum/minimum temperature fluctuation was observed. Chironomids were the dominant forms emerging during the period of investigation, 51 species were recorded but only five were present in significant numbers; 19 Trichopteran species were taken, but only four in significant numbers; one species each of Chaoboridae and Ephemeroptera was taken. There does not appear to be a direct correlation between high temperatures and peak emergence within the Chironomidae, however the peak emergence of Chaoborus flavicans in Lough Avaul coincides with the maximum temperature recorded (15 C). Differences in peak emergence periods of some similar species in different lakes are apparent.
    • An Investigation into the Chemical and Biological Effects of Pollution in the River Tolka

      O'Connor, M. A.; Bracken, J. J. (Department of Agriculture and Fisheries [Fisheries Division], 1980)
      Physico-chemical and biological sampling show that the River Tolka is affected by organic pollution over most of its length. Domestic sewage is the major contaminant. A distinct zonation of the river is noted as certain polluted areas are succeeded by downstream recovery zones. Many of the effluents and tributaries are investigated. Oxygen depletion and excessive ammonia concentrations are the factors most likely to have caused the observed faunal changes.
    • Irish Kelt Tagging Experiments

      Went, A. E. J. (Department of Agriculture and Fisheries [Fisheries Division], 1969)
      Since the beginning of the century large numbers of salmon kelts have been tagged in Irish waters and the results have been given in a series of papers...a considerable number of kelts have been tagged since 1962 at a number of stations in Ireland and they form the basis of this paper.
    • Irish Pike Investigations

      Kennedy, M. (Department of Agriculture and Fisheries [Fisheries Division], 1969)
      The spawning of pike was studied in 1965 and 1966 in five large Irish limestone lakes-Loughs Sheelin, Ennell, Mask, Corrib and Arrow. The spawning period was found to be February to April. Spawning took place in shallow, sheltered situations where there was a carpet of dead or living vegetation on the bottom at a depth of 20 to 60 cm. Spawning took place by day, at a water temperature of at least 9-1O C, when lake levels were high or rising. Gill-net catches reached a peak during periods of spawning. Weather conditions in February and March were much milder in 1966 than in 1965, and spawning began about a month earlier than in 1965. The eggs of Irish pike are 2.7 to 3.0 cm in diameter. They are golden to honey coloured, with a great many minute oil-globules distributed through the yolk in numerous tiny clusters. The incubation period in the field is probably 8-14 days, and the newly hatched larva is 8.0-9.0 mm long. For the first 10 days or so, the larvae hang vertically from the vegetation by means of adhesive glands on the head. They then become free-swimming, and soon afterwards begin to feed. At this stage they measure 13.0-13.5 mm. Their first food consists of small cladocera and copepods. Later, they feed on larger cladocera, amphipods, isopods, young stages of aquatic insects, and fish fry.
    • A List of Rotatoria Known to Occur in Ireland with Notes on Their Habitats and Distribution

      Horkan, J. P. K. (Department of Agriculture and Fisheries [Fisheries Division], 1981)
      A total of 315 species of rotifers are known to occur in Ireland. Of these 71 belong to the Bdelloidea and 244 to the Monogononta. Three species new to Ireland are now recorded and one of them is also a new record for the British Isles. A taxonomic list of the 315 species is given together with notes on ecology, where possible, and distribution. The names of recorders are included.