• Population estimates of juvenile salmonids in the corrib system 1980

      Browne, J; Gallagher, P (Department of Fisheries and Forestry, 1981)
      Population assessments of the juvenile salmonids in the Corrib System are being made as part of the overall management plan for the Galway Fishery. In 1980 the first of a series of reports which will be issued annually gave information on the juvenile stocks and on the state of the spawning and nursery tributaries during 1979. Details of the methods used and some background on each of the tributaries were presented. Chemical and biological data on water quality along with numbers, size, age and survival of both salmon and trout are given in Fishery Leaflet 103. During 1979 eight tributaries were surveyed and in two cases upstream and downstream reaches were examined. In 1980 the effort in terms of personnel and equipment was increased but the high rainfall during the period of work, from mid-July to mid-September, meant that only two further stations were studied, one on the Dalgan river and the other on the Balinbrack river. The methods used and the scope of the work were identical in 1979 and 1980. In these assessments the emphasis is on salmon type tributaries and salmon type habitats within these tributaries so that trout numbers could be expected to be low.
    • Population estimates of juvenile salmonids in the Corrib system 1981

      Browne, J; Gallagher, P (Department of Fisheries and Forestry (Trade and Information Section), 1982)
      This is the third in a series of reports regarding the stocks of juvenile salmonids in the Corrib system. During the 1981 season fourteen tributaries were surveyed and in two cases upstream and downstream reaches were examined. These included three which had not been studied previously: the Failmore, Letterfore and Black. The methods were identical to those used in 1979 and 1980. As in the previous years the rivers were selected because they were known salmon holding tributaries and do not reflect trout numbers in the system. The population numbers are assessed by electrically fishing a selected area. The fish caught are marked by fin clipping and allowed to re-mix with the fish in the stream. The next day fishing is repeated in the same place and the proportion of marked to unmarked fish gives an estimate of the population. While it is not essential that river conditions remain the same on both days it does help the accuracy of the estimate. There is a tendency for fish to move out of their home territories during floods. Population surveys yield the best results when a large proportion of the tagged fish are recovered. Ideal electro fishing conditions are low water, overcast sky and similar river conditions on both days.
    • Populations Estimates of Juvenile Salmon in the Corrib System from 1982 to 1984

      Browne, J; Gallagher, P (Department of Tourism, Fisheries and Forestry, 1987)
      This leaflet gives the details of juvenile salmonid densities for the years 1982 to 1984 in the Corrib system. In general, since these investigations began in 1979, the Corrib tributaries have appeared to be adequately stocked with salmon. The salmon densities in the rivers to the west of Lough Corrib are much higher than in the rivers to the east. However, survival is higher in the latter. A detailed survey of juvenile salmon habitat revealed that there are 392,000 square metres of suitable habitat in the system. Of this 253,000 square metres are on the west side and 139,000 on the east side.
    • Preliminary Investigation of the Population of Juvenile Salmonids in the Corrib System

      Browne, J; Gallagher, P (Department of Fisheries and Forestry (Trade and Information Section), 1980)
      Population assessments of the juvenile salmonids in the Corrib system are being made as part of the overall management plan for the Galway Fishery. This leaflet is the first of a series of reports which will be issued annually to give up-to-date information on the stocks and on the state of the tributaries used for spawning and nursery grounds. Eight tributaries were surveyed in 1979 and in two cases an upstream and a downstream reach were examined.
    • Results of Magnetic tag Recovery Programme in the Mayo Area in 1985

      Gallagher, P (Department of Tourism, Fisheries and Forestry, 1986)
      This leaflet deals with the results of the magnetic tag recovery programme for the Mayo area in 1985. The commercial salmon catch was sampled for adipose fin clipped and micro tagged fish at a number of locations in Mayo. All fish with adipose fin clips were screened with a magnetic tag detector for tags, and the tags were read to establish the origin of the fish. Fish are tagged at various locations throughout the country with magnetic wire tags. These tagged fish are released at different times of the year, and in various river systems to establish the best time of year to release fish and the best locations. The majority of all the tagged fish are hatchery reared, only in the Corrib river are wild fish tagged.
    • Results of Magnetic Tag Recovery Programme in the Mayo Area in 1986

      Gallagher, P; Browne, J (Department of the Marine, 1987)
      Young salmon are tagged at various locations throughout the country with coded wire tags. They are released at different times of the year, and in various river systems to establish the best time of year and the best locations for release. The majority of the tagged fish are hatchery reared, the only exception being in the Corrib and Blackwater rivers where wild smolts are tagged. All micro-tagged fish are adipose fin clipped. Some hatcheries also use an adipose fin clip to mark their reared fish. Twenty nine thousand net caught salmon were examined at a number of locations in Mayo. All fish with adipose fin clips were screened with a magnetic tag detector. A total of 736 tags were recovered from which it was estimated that rearing stations contributed over 1,300 fish to the north Mayo catch.