• 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.
    • The fat content of Irish herring

      Molloy, J; Cullen, A (Department of Fisheries and Forestry (Trade and Information Section), 1981)
      The fat content in herrings determines the way in which these fish are presented for human consumption. For example, a high fat content is good for kippering, whilst low fat is suitable for marinating. The Department of Fisheries & Forestry has for many years provided the trade with the fat content data they require. The information is based on routine analyses of herring samples which are now made regularly at the Fisheries Research Centre. Sufficient data have been collected over the past ten years to prepare graphs of the mean monthly fat contents in our four main herring fisheries. These graphs may be used to estimate when herring of a particular fat content will be available. This Leaflet presents the essential data and gives an explanation of the biological background of the changes in fat content.