• Monitoring of Shellfish Growing Areas - 1994

      Nixon, E; McLaughlin, D; Rowe, A; Smyth, M (Department of the Marine, 1995)
      To fulfil the monitoring requirements of the 1979 Council Directive 79/923/EC on the water quality of shellfish waters, water and shellfish samples were collected from 19 major shellfish-growing areas and analysed for physicochemical parameters and chemical contaminants. At each site temperature, salinity, pH and dissolved oxygen measurements were made and the area was inspected for the presence of petroleum hydrocarbons. Water samples were collected for suspended solids determinations. A representative sample of the shellfish from each area was collected and returned to the laboratory for metal and chlorinated hydrocarbon analyses. As in previous years, the water quality was good and conformed to guidelines and requirements of the Directive. Petroleum hydrocarbons were not observed in any of the shellfish waters or as deposits on the shellfish. Chlorinated hydrocarbon levels were very low, evidence of the clean, unpolluted nature of Irish shellfish and shellfish producing waters. Mercury and lead levels were consistently low, however, levels of cadmium in oysters from a number of areas were above average but did not exceed the Dutch human consumption tolerance value. It is known that oysters accumulate metals more readily than mussels and, considering the remoteness of many of these areas, the elevated cadmium levels are not considered to be anthropogenic in origin.
    • Monitoring of Shellfish Growing Areas - 1995

      Smyth, M; Rowe, A; McGovern, E; Nixon, E (Marine Institute, 1997-08)
      In accordance with the monitoring requirements of the 1979 Council Directive 79/923/EC on the water quality of shellfish waters, water and shellfish samples were collected from 21 major shellfish-growing areas and analysed for physicochemical parameters and chemical contaminants. At each site temperature, salinity, pH and dissolved oxygen measurements were made and the area was inspected for the presence of visible petroleum hydrocarbons. Water samples were collected for suspended solids determinations. A representative sample of the shellfish from each area was collected and returned to the laboratory for metal and chlorinated hydrocarbon analyses. As in previous years, the water quality was good and conformed to guidelines and requirements of the Directive. Petroleum hydrocarbons were not observed in any of the shellfish waters or as deposits on the shellfish. Chlorinated hydrocarbon levels were very low, evidence of the clean, unpolluted nature of Irish shellfish and shellfish-producing waters. Mercury and lead levels were consistently low. Levels of cadmium in oysters from a number of areas were slightly elevated but did not exceed the Dutch human consumption tolerance value of 1mg/kg (ppm) wet weight.
    • 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.
    • Mulroy Bay Scallop Research 1980

      Griffith, David de G (Department of Agriculture and Fisheries (Fisheries Division), 1981)
      Following a preliminary investigation in 1977, the Department of Fisheries & Forestry carried out an intensive multi-disciplinary survey of Mulroy Bay in the summer of 1978. The results of this "blitz" survey, when evaluated, formed the basis of more extensive research in the North Water during 1979. This North Water programme was expanded in 1980, as part of the Department's contribution to a co-operative research programme on Mulroy Bay organised in conjunction with the National Board for Science & Technology. This included a hydrographic survey, specially commissioned by the Department, to produce a detailed bathymetric chart of the North Water. This was made available free of charge to interested individuals and groups in the locality. The 1980 research results were presented at a seminar in January 1981 at the Department's Fisheries Research Centre, which was organised in order that the data obtained could be discussed and evaluated by the individuals and agencies involved in the field programme. This Fisheries Leaflet is a summary of the papers read at that seminar, by staff of the Fisheries Research Centre.
    • National activities in the field of Aquaculture: Ireland

      Griffith, David de G (ed) (Marine Institute, 1996-05)
      This document was prepared in May 1995 by a group of invited aquaculture experts drawn from the Irish aquaculture industry, the Fisheries Research Centre, An Bord Iascaigh Mhara, Salmon Research Agency, Veterinary Research Laboratory, the Marine Institute and from University RTD laboratories. It was drafted as a contribution to the 1995 meeting of Directors of Fisheries Research Organisations of the European Union, and as a response to a review by DG XIV entitled "European Aquaculture Research: current position and prospects” (COM(94) 258 final).
    • National Survey of the Sea Lice (Lepeophtheirus salmonis Krøyer and Caligus elongates Nordmann) on Fish Farms in Ireland - 2000

      McCarney, P; Copley, L; Jackson, D; Nulty, C; Kennedy, S (Marine Institute, 2001-09)
      Fanned fish can be divided into three distinct groups, rainbow trout and two year classes (or generations) of salmon. In terms of husbandry and lice management, salmon which are at sea for a year or longer in April (growers/one-sea winter) are treated separately from younger salmon (smolts) and rainbow trout. Those salmon that were put to sea in winter 1999/spring 2000 are referred to as smolts, or 2000 year class fish. The farms were inspected twice a month in March, April and May and once a month thereafter, with one exception, December/January where sites were visited only once. Two species of lice are commonly found on cultured salmonids, Caligus elongates Nordmann, a species of parasite that infests over fifty different species of marine fish, and Lepeophtheirus salmonis Krøyer, which infests only salmon and closely related species such as rainbow trout. Lepeophtheirus salmonis, the Salmon Louse, is regarded as the more serious of the two species and occurs most frequently on Irish cultivated salmon (Jackson and Minchin, 1992). Results for both species are given for each sampling period. These sea-lice inflict damage to their hosts through their feeding activity on the host's body (Jones et al., 1990; Jonsdottir et al., 1992; Kabata, 1974) and significant economic losses were attributed to these copepod ectoparasites by Roth et al. (1993). Lepeophtheirus salmonis is a member of the Family Caligidae and has a direct lifecycle (i.e. a single host). This life-cycle comprises ten stages. Following hatching from paired egg strings, two free-living nauplius stages are dispersed into the plankton. These stages are followed by a copepodid stage where contact with the host takes place. The copepodid then moults through four chalimus stages before becoming a pre-adult male or female. This pre-adult phase comprises two stages and is followed by the fully mature adult phase. The adult female can produce a number of batches of paired egg-strings which in turn hatch into the water column to give rise to the next generation (Kabata, 1979; Schram, 1993).
    • National Survey of the Sea Lice (Lepeophtheirus salmonis Krøyer and Caligus elongates Nordmann) on Fish Farms in Ireland - 2001

      McCarney, P; Copley, L; Kennedy, S; Nulty, C; Jackson, D (Marine Institute, 2002-02)
      Two species of lice are found on cultured salmonids, Caligus elongatus Nordmann, a species of parasite that infests over fifty different types of marine fishes, and Lepeophtheirus salmonis Krøyer, which infests only salmon and other salmonids. The Salmon Louse (L. salmonis) is regarded as the more serious parasite of the two species and has been found to occur most frequently on Irish farmed salmon (Jackson and Minchin, 1992). Most of the damage caused by these parasites is thought to be mechanical, carried out during the course of attachment and feeding (Kabata, 1974; Brandal et al., 1976; Jones et al., 1990). Inflammation and hyperplasia (enlargement caused by an abnormal increase in the number of cells in an organ or tissue) have been recorded in Atlantic salmon in response to infections with L. salmonis (Jones et al., 1990; Jonsdottir et al., 1992; Nolan et al., 2000). Increases in stress hormones caused by sea lice infestations have been suggested to increase the susceptibility of fish to infectious diseases (MacKinnon, 1998). Severe erosion around the head caused by heavy infestations of L. salmonis has been recorded previously (Pike, 1989; Berland, 1993). This is thought to occur because of the rich supply of mucus secreted by mucous cell-lined ducts in that region (Nolan et al., 1999). In experimental and field investigations carried out in Norway heavy infestation was found to cause fish mortalities (Finstad et al., 2000). Lepeophtheirus salmonis (Caligidae) has a direct life cycle, meaning it uses a single host. After hatching from the egg (which is extruded from the adult female louse in paired egg strings) two free-living nauplii stages are dispersed into the water column. A copepodid stage then follows during which a host must be located before the parasite can develop further. After finding a host the copepodid moults through four chalimus stages, which all occur while the parasite is attached to the host, before developing into a mobile pre-adult male or female. A moult then separates two pre-adult stages after which the fully mature adult develops. The adult female is capable of producing a number of batches of paired egg-strings during her life-span, which in turn hatch into the water column giving rise to the next generation. This gives a total of ten stages through which the parasite must develop to reach adulthood (Kabata, 1979; Schram, 1993). Caligus elongatus is a non-host specific parasite and can be found on many different fish species (Kabata, 1979). It has a similar life cycle to that of L. salmonis (Hogans and Trudeau, 1989). Four groups of farmed fish were examined during sea-lice inspections in 2001. These include rainbow trout, salmon smolts (200 I generation), one sea-winter salmon (2000 generation) and two sea-winter salmon (1999 generation). S1/2's or half year smolts are fish which are transferred to sea in Autumn/Winter of the same year that they are hatched, they smoltify early due to a photoperiod manipulation (Willoughby, 1999). Their S1 siblings smoltify and are put to sea in early spring. S1/2's are included in each year class of fish for the purpose of analyses.
    • National Survey of the Sea Lice (Lepeophtheirus salmonis Krøyer and Caligus elongates Nordmann) on Fish Farms in Ireland - 2002

      O'Donohoe, P; Kennedy, S; Copley, L; Kane, F; Naughton, O; Jackson, D (Marine Institute, 2003)
      Salmonids farmed in Ireland in 2002 can be divided into the following groups: one year class of rainbow trout Oncorhynchus mykiss and three year classes of Atlantic salmon Salmo safar. The year classes of salmon include, smolts (2002 generation), one sea-winter salmon (2001 generation) and two sea-winter salmon (2000 generation). S1/2' s are fish which are transferred to sea in Autumn/Winter of the same year that they are hatched. Their S1 siblings smoltify and are put to sea in early spring, some three to four months later. Salmon which are at sea for a year or longer in April are known as growers/one sea-winter and are treated separately from younger salmon (smolts) and rainbow trout. Those salmon that were put to sea in winter 200 I /spring 2002 are referred to as smolts, or 2002 year class fish. During the 2002 sampling period all four groups of farmed fish were examined. Two species of sea lice are found on cultured salmonids in Ireland, Caligus elongates Nordmann, a species of parasite that infests over eighty different types of marine fish, and Lepeophtheirus salmonis Krøyer, which infests only salmon and other salmonids. Sea lice are regarded as having the most commercially damaging effect on cultured salmon in the world with major economic losses to the fish farming community resulting per annum (Bristow and Berland, 1991; Jackson and Costello, 1991). They affect salmon in a variety of ways: mainIy by reducing fish growth, loss of scales which leaves the fish open to secondary infections (Wootten et aI., 1982) and damaging of fish which reduces marketability.
    • National Survey of the Sea Lice (Lepeophtheirus salmonis Krøyer and Caligus elongates Nordmann) on Fish Farms in Ireland - 2003

      O'Donohoe, P; Kennedy, S; Kane, F; Naughton, O; Tierney, D; Copley, L; Jackson, D (Marine Institute, 2004)
      Sea lice are regarded as having the most commercially damaging effect on cultured salmon in the world with major economic losses to the fish farming community resulting per annum (Bristow and Berland, 1991; Jackson and Costello, 1991). They affect salmon in a variety of ways; by reducing fish growth; by causing loss of scales, which leaves the fish open to secondary infections (Wootten et al., 1982); and by damaging the fish, which reduces its marketability. The two species of sea lice found on cultured salmonids in Ireland are Caligus elongatus Nordmann, a species of parasite that infests over 80 different types of marine fish, and Lepeophtheirus salmanis Kroyer, which infests only salmon and other salmonids. L. salmonis is regarded as the more serious parasite of the two species and has been found to occur most frequently on farmed salmon (Jackson and Minchin, 1992). Most of the damage caused by these parasites is thought to be mechanical, carried out during the course of attachment and feeding (Kabata, 1974; Brandal et al., 1976; Jones et al., 1990). Inflammation and hyperplasia (enlargement caused by an abnormal increase in the number of cells in an organ or tissue) have been recorded in Atlantic salmon in response to infections with L. salmonis (Jones et al., 1990; Jonsdottir et al., 1992; Nolan et al., 2000). Increases in stress hormones caused by sea lice infestations have been suggested to increase the susceptibility of fish to infectious diseases (MacKinnon, 1998). Severe erosion around the head caused by heavy infestations of L. salmonis has been recorded previously (Pike, 1989; Berland, 1993). This is thought to occur because of the rich supply of mucus secreted by mucous cell-lined ducts in that region (Nolan et al., 1999). In experimental and field investigations carried out in Norway heavy infestation was found to cause fish mortalities (Finstad et al., 2000).
    • The Parasitology of Irish Mussels

      Crowley, M (Department of Agriculture and Fisheries (Fisheries Division), 1972)
      Investigations of the distribution of three parasites of mussels, an internal copepod parasite of the gut (Mytilicola intestinalis), an external decapod parasite in the gill region (Pinnotheres pissum) and an analid shell parasite (Polydora ciliata) were carried out from October 1971 to April 1972. Samples from 26 locations around the Irish coast were investigated. One hundred mussels from each sample were weighed, measured in 5 mm groups, boiled and the following were estimated as percentages of the whole mussel:- a. Shell; b. Meat; and c. Loss.
    • Parasitology of Irish Mussels

      Crowley, M (Department of Agriculture and Fisheries (Fisheries Division), 1975)
      Investigations of the distribution of three parasites of mussels, an internal copepod parasite of the gut (Mytiliocola intestinalis), an external decapod parasite in the gill region (Pinnotheres pissum) and an annelid shell parasite (Pylodora ciliata) were carried out from September 1974 to May 1975. Samples from 28 locations around the Irish coast were investigated. One hundred mussels from each sample were weighed, measured in 5 mm groups, boiled and the following parameters were determined as percentages of the whole mussel:- a. Shell: b. Meat; c. "Loss"
    • Performance of the Crumlin sea-trout Fishery, Co. Galway

      Fahy, E (Department of Agriculture and Fisheries (Fisheries Division), 1979)
      The physical features of the Crumlin catchment, a small sea-trout fishery in Co. Galway, are described. Its sea-trout stock is examined and found to be typical of others in the region: the fish are slow growing in the sea, poorly conditioned, mortality in the stock is high and the fish have a low weight at capture. Fishery statistics date from 1896. The main influence on the numbers taken by anglers appears to have been the two wars. Individual catch weights do not show any inverse relationship with catch numbers of the kind that has been reported already in the vicinity. Catch per effort has not altered in keeping with any identifiable long-term trend but is within the range recently reported elsewhere in the region. Regulations designed for the protection of smolts in past years also protect about 20% of post-smolts (finnock) currently captured. Yield from Crumlin has most in common with output from a small neighbouring fishery. It is tentatively suggested that sea-trout production from the Connemara catchments is dependent primarily on the physical features of the systems concerned.
    • 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.
    • Prawn Fishing

      Gibson, F A (Department of Lands, 1956)
      The common prawn (Leander serratus) is widely distributed around the Irish coasts, but obviously varies in abundance from place to place. This prawn should not be mistaken for the Norway Lobster, sometimes called the Dublin Bay Prawn (Nephrops norvegicus) or with the brown shrimp (Crangon vulgaris). Alive, the common prawn is a grey-brown colour and has blue bands on its legs. The Norway lobster is a pink colour, and its body is profusely covered with white tipped spines. The common prawn also has a projection from its head, called a rostrum, which is absent from the shrimp. As the prawn is of economic importance, some notes on simple methods of capture will be of interest to fishermen.
    • Preliminary Catch, Discards and Selectivity Results of Trawl Survey on Deepwater Slops of the Rockall Trough

      Clarke, M W; Connolly, P L; Kelly, C J (Marine Institute, 1999-10)
      A deepwater trawl survey programme has been operated since 1993 by the Fisheries Research Centre (FRC) in the deep waters of the Rockall Trough and Porcupine Bank. The present survey took place over a period of 10 days in October and November 1997 on the eastern and southern slopes of the Rockall Trough from 54°N to 59°N. Fishing was carried out in five separate areas, in four depth strata: 500-700m, 700-900m, 900-1100m and 1100-1300m. The primary objective of the survey was to obtain samples of chondrichthyan and teleost fish for the FRC deepwater research programme, for contaminant analysis offish by the FRC chemistry section and for food technology analysis at the Teagasc National Food Centre. The survey was carried out on a commercial trawler using commercial deepwater demersal otter trawl gear. In total 15 species of chondrichthyan, 41 species of teleost fish and 5 species of cephalopods were taken. Among the most abundant species in the catch were roundnose grenadier, Portuguese dogfish, leafscale gulper shark, and Baird's smoothhead. Over the entire survey discarding was estimated as 50.5% of the total catch. Discard rates expressed as kg discarded per tonne roundnose grenadier landed and as a percentage of the total catch when compared with those of previous years showed no appreciable change. The main species discarded were rabbitfish, birdbeak dogfish, Baird's smoothhead, roundnose grenadier and Lepidion eques. Catch per unit effort rates expressed as kg caught per hour fished compared with rates for previous trawl surveys showed marked declines. Length frequency distributions for the main chondrichthyan species showed absence of smaller individuals from the samples and sexual dimorphism with respect to length. Attachment of fine-mesh cod-end liner suggested that the commercial gear selects all length frequencies present and that mesh size may not be an effective management measure in this fishery. This leaflet documents the survey and presents some preliminary results. The data from this survey are currently under analysis at the FRC and results will be published in the scientific literature.
    • 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.
    • Preliminary Investigations of the Sprat stocks off the South coast of Ireland

      Molloy, J; Bhatnagar, K (Department of Agriculture and Fisheries (Fisheries Division), 1977)
      The development of a new fishery for sprat off the south coast is reviewed. The fishery during 1976 and 1977 produced over 1,600 tons of sprat, valued at over £92,000. The quality of sprat landed was excellent throughout the fishing period. While it is difficult to estimate the size of the stock in the area, it would appear that landings could be substantially increased. This, together with the quality of the sprat, could make this fishery a valuable alternative to the Celtic Sea herring fishery.