• The effects of drainage on the flora and fauna of a tributary of the River Boyne

      McCarthy, D T (Department of Agriculture and Fisheries (Fisheries Division), 1975)
      Arterial drainage helps in the process of land reclamation by lowering the level of the existing river bed and allowing the ground water to run off more quickly. In recent years the Rivers Corrib, Dee-Glyde, and Moy have been drained. The effects of drainage on the fish stocks and the invertebrate fauna of the River Moy have been described by Toner, 0'Riordan and Twomey (1965). In 1968 investigations commenced into the effects of drainage on the invertebrate fauna and flora as well as fish stocks in the Trimblestown, or Athboy, River, a tributary of the River Boyne. The Boyne rises 6.4 km from Edenderry and flows north-east for 112 km to the sea at Drogheda. It has fifteen tributary streams and two lakes in its catchment area of 2,693 square km. A section of the Trimblestovn River which rises at the foot of Slieve na Calligh, Co Westmesth and flows south-east for 35 km to meet the Boyne at the town of Trim was selected. Its shallowness and accessibility made it particularly suitable for the study. The study area 4.8km north of Athboy town, was 146 metres long and averaged 6.1 metres wide. The river flows for its entire length over Carboniferous limestone end the bed of the river consists of gavel and sandy silt, with scattered boulders and some mud in the quieter areas. There are a few pools in this section, the river being composed of riffle areas alternating with flats. The normal flow at this point was 0.77 cubic metres per second, the pH was 7.6 and the alkalinity as CaCo3 was 310 p.p.m. From 1968 and 1970, 57 invertebrate fauna samples from standard areas (0.093 sq.m) were taken with a suber stream bottom sampler. The plant life was mapped and an assessment of the fish population was made, by the depletion method.
    • Fish Kills 1969-1987

      McCarthy, D T (Department of the Marine, 1988)
      A total of 66 fish kills were reported to the Regional Fisheries Boards in 1986 and 122 in 1987. Effluents from agriculture and agriculture-based industries accounted for 56 of the kills in 1986 and 95 in 1987. When the two periods, 1969-74 and 1980-87 are compared, it can be seen that the numbers caused by sewage and industrial wastes have not changed significantly, but the damage from agriculture has risen at an alarming rate. The fact that problems from sewage and industry remained at a low level in the period, in spite of increasing urbanisation, suggests that measures to combat these sources of pollution have had some effect. Analysis of the fish kills shows clearly that the most urgent problem is to discover how silage effluent can be controlled.
    • Interaction between seals and salmon drift net fisheries in the west of Ireland

      McCarthy, D T (Department of Fisheries and Forestry, 1985-05)
      The common seal Phoca vitulina L. and the grey seal Halichoerus grypus F. are both present in colonies along the west coast. The common seal inhabits bays and estuaries and inlets with sandy bars mainly in Galway Bay, Clew Bay, Co. Mayo, Ballysadare Bay, Co. Sligo and Donegal Bay. The grey seal is more widely dispersed particularly in the summer months and can be seen in bays, estuaries and offshore islands. Widespread complaints by salmon fishermen in Galway Bay of severe predation by seals on salmon caught in drift nets in 1978 led to a programme to study the problem. In 1979 and 1981 direct observations on board two salmon drifters were made in Galway Bay and in 1980 and 1981 similar work took place on three boats in Sligo Bay. In addition, two crews were interviewed in port each evening. In 1980 salmon landed in Donegal, Galway and Kenmare were examined at market points and the number of seal damaged fish recorded. This leaflet gives the results of the study and concludes that effective control requires measures against the seals which are actually robbing the nets. Destruction of seals at breeding colonies is unlikely to have any positive effect on the rate of predation.
    • Movement of Salmon from the South Coast in 1975

      McCarthy, D T (Department of Agriculture and Fisheries (Fisheries Division), 1977)
      In 1973, tagging investigations commenced into the origin of the salmon stocks being exploited by drift nets along the south coast of Ireland (8º0’W - 10º0’W). The exploitation of these stocks commenced in 1968 with a catch of 1,500 fish and by 1975 the catch had increased to 90,400. The results of the 1973-1974 programme and a description of the fishing methods used have been published in Fishery Leaflet No. 67. Throughout the programme, fish were tagged using Lea’s hydrostatic tags described by Went (1951). A marked difference in returns was observed in 1975 between salmon revived in sea water tanks and those released directly after tagging, In the former, a 14.8% recapture rate was recorded, compared with 6% in the case of salmon released immediately after tagging.
    • Movement of salmon from the south coast of Ireland in 1973-1974

      McCarthy, D T (Department of Agriculture and Fisheries (Fisheries Division), 1975)
      In 1973 tagging investigations were started into the origin of the salmon stocks being exploited in the West Cork area (8º0'W to 10º10'W) along the south coast of Ireland. The vessels used varied from six metre open boats to twenty metre trawlers, the average length was 10.5 metres (1972 survey involving 276 boats). Fishing is carried on over the twenty four hours. Up to 1973 nets were 30 mashes deep: in that year nets of 60 and up to 98 meshes were introduced, and during the 1974 season most boats fished nets of 68 meshes deep. The length of net varied from 400 metres to 1.6 km. Nets were shot at right angles to the coast in roughly a north-south direction, all vessels staying quite close to land, the furthest distance out being approximately 2 km from land. Most fish were caught in the bottom portion of the net during the hours of day-light but at night or in rough weather about half the catch were caught in the top portion of the net.
    • Salmon movements in Galway Bay in 1978 and 1979

      McCarthy, D T (Department of Agriculture and Fisheries (Fisheries Division), 1980)
      In 1978 tagging investigations commenced into the origin of salmon caught in drift nets in Galway Bay. This fishery began in 1969 with a catch of 355 fish and, by 1975 had increased dramatically to 33,607. However the catch declined to less than half the maximum and in 1979 was down to 15,171. There are 76 drift net licences in the Bay which incorporates two fishery districts, Galway and Connemara. The vessels used vary from 5 metre currachs to 20 metre trawlers. The majority of the boats are half deckers of between 9 and 11 metres. The fishery starts in mid-May but the bulk of the catch is taken in June and July. The main component of the catch is grilse with an average weight of 3 kg. During the period fishing is carried on over 24 hours daily except for the weekly close season time. The fishery extends from west of a straight line from Spiddal Harbour to Blackhead, Co Clare in the east , and from Slyne Head to Hag's Head, Co. Clare in the west and also incorporates the Aran Islands. Drift nets are shot at right angles to the coastline in roughly a north-south direction, all vessels staying quite close to land, the furthest distance out being 2km. The maximum length of net permitted in the area is 730 metres or 800 yards. The majority of boats fished nets of this length; however some of the smaller craft used nets as short as 300 metres. All nets are 30 meshes deep. Throughout the programme fish were tagged using Lea's hydrostatic tags described by Went (1951). As in previous tagging programmes, recovery baths were used to ensure that only the fittest fish were released after tagging.