• Exploitation and Survival of Reared Salmon Released into the Burrishoole River System

      O'Maoileidigh, N; Browne, J; Cullen, A; McDermott, T; Keatinge, M (Department of the Marine, 1994)
      Hatchery reared salmon smolts have been microtagged using binary coded nose tags and released into Irish rivers since 1980. These tagged fish are intercepted and identified in high seas coastal fisheries and in Irish rivers as adult salmon. The tag recovery programme provides valuable information on the marine survival and exploitation rates of these tagged fish and the return rates back to the river of origin. This leaflet summarises the results for release groups of reared indigenous salmon from the Burrishoole system in Co. Mayo. Marine survival prior to homewater exploitation has been very variable in the period examined. Although homewater marine exploitation rates have varied considerably depending on the fishing areas, they remained high for all areas combined between the years 1982 to 1989 with exploitation rates by coastal fisheries up to 87%. The greater part of the catch is taken in the Mayo area. Exploitation rates have decreased since 1989 and approximately 60% of the returning stock is estimated to have been caught in coastal fisheries in 1993. Survival to the river has also varied with an average of 2.5% of the total number of smolts released returning as adults to the river.
    • Exploitation and Survival of River Shannon Reared Salmon

      O'Maoileidigh, N; Browne, J; McDermott, T; Cullen, A; Bond, N; McEvoy, B; O'Farrell, M; O'Connor, W (Department of the Marine, 1994)
      Following the construction of the River Shannon hydroelectric scheme the Electricity Supply Board (ESB) have maintained a juvenile salmon restocking programme. Tagging of smolts with coded wire tags (microtags) was initiated in 1980 to examine the migration and survival of these stocked fish. In 1991, an estimated 292,000 hatchery reared salmon smolts (micro tagged and adipose finclipped) migrated from the River Shannon, County Limerick. This allowed an assessment to be made of the contribution of these fish to the high seas fisheries at West Greenland and Faroes, and also to homewater net and rod fisheries. Over 12,000 grilse from this release programme were estimated to have been taken by commercial nets with 525 taken on rods and 3,147 surviving to spawn. The return rate of 2 sea winter fish was much lower with 150 taken by commercial nets, 93 taken by rods and 202 estimated to have spawned. The Greenland fishery took approximately 107 potential 2 sea winter fish which is a high proportion of the overall 2 sea winter stock. Tag returns from groups of smolts released by helicopter proved to be highest. Groups released above the dams and which had to navigate through these installations also showed comparatively good returns. Early presmolt and smolt releases (i.e. December and February) did not give as good return rate in comparison to the other release groups.
    • Salmon Tagging in the West of Ireland 1986 to 1988

      McDermott, T (Department of the Marine, 1990-07)
      The analysis of more than twenty-six thousand micro-tag recoveries has led to important discoveries for the management of Irish salmon stocks. This Leaflet gives details of the tagging over half a million young salmon and of the results of recovering 4,000 tags from 1986 to 1988. The most important conclusions are: Careful control of place and time of release of hatchery-reared smolts has a dramatic effect on their survival. In the Corrib system, transportation of smolts from Cong to Galway resulted in a substantial improvement in yield, with a tenfold increase on one occasion. This means that up to ten times as many salmon can be produced at no increase in the cost of rearing them. The returning adult salmon produced from smolts which were released at Galway tended to stay for a long time below the Galway weir and therefore made a major contribution to the rod fishery. Marine survival fluctuated yearly for hatchery and wild smolts released. For hatchery smolts those released later survived best. In contrast wild smolts which migrated in May had a lower survival than those which left in April. Marked differences in homing accuracy, timing and speed of migration were noted between wild and hatchery smolts within the Corrib system. Drift net fisheries depend mainly on the salmon which originate from rivers nearby. There is a distinct division between the catches north and south of Galway Bay: those to the south come mostly from the rivers Shannon and Corrib, those to the north from Connemara rivers. The drift net fishery continues to rely heavily on a self sustaining population of wild salmon despite improved hatchery performance and increasing catch of cage farm escapees. Hatchery smolts transferred to different rivers learned to recognise the new river within a remarkably short time. Two weeks were sufficient to achieve a degree of homing success approaching that of fish returning to their own rivers. This discovery is of major significance in the development of salmon ranching.