• Irish Sprats and Sandeels

      Molloy, J (Department of Agriculture and Fisheries (Fisheries Division), 1967)
      In 1965, Ireland imported approximately 13,235 tons of fishmeal for animal feeding stuffs, valued at £827,506. For some time now cosideration has been given to the fish resources around our coasts and whether it would be possible to provide a constant source of supply of materials to the fishmeal industry and the growing number of mink and trout farms. This paper investigates this issue.
    • Notes On Some Irish Estuarine And Inshore Fishes (With records of the distribution of shads by Eileen Twomey, M.Sc )

      Bracken, J J; Kennedy, M (Department of Agriculture and Fisheries (Fisheries Division), 1967)
      This paper brings together data collected in various ways by the authors, over a period of years. Some of the material described is a by-product of investigations, the primary results of which have already been published. Other material is supplementary to data previously published.
    • Irish Investigation on the Lobster (Homarus vulgaris Edw.)

      Gibson, F A (Department of Agriculture and Fisheries (Fisheries Division), 1967)
      Commercially the lobster (Homarua vulgaris Edw.) is the most important shellfish in Ireland. The Irish coast is deeply indented, except on the east, and is well suited for the exploitation of lobsters. Even on the east coast amidst a predominantly sandy shoreline, a number of discreet areas are fished actively.
    • Stocks of Nephrops norvegicus off the south coast of Ireland

      Gibson, F A (Department of Agriculture and Fisheries (Fisheries Division), 1967)
      Nephrops norvegicus is also known popularly as the Dublin Bay Prawn or Norway Lobster. The stocks of prawns in depths down to 60 fathoms (109m) have been studies since 1956, off the south of Ireland, from Mine Head, Co. Waterford, to the Kenmare River, Co. Kerry. The present paper is concerned with data obtained from the research vessel Cú Feasa, together with other samples collected from commercial fishing boats, during the years 1963 to 1966 inclusive.
    • The Whiting Fishery Off Counties Dublin and Louth On the East Coast of Ireland

      Hillis, J P (Department of Agriculture and Fisheries (Fisheries Division), 1968)
      The whiting Merlangius merlangus (L) has for over 30 years been the leading demersal species by weight in the landings of commercial fisheries on the east coast of Ireland. The present study was commenced in the autumn of 1959, using samples of both the commercial fishery and the research vessel Cú Feasa. The present paper describes the commercial catch from port samples supplemented with research vessel material where extra detail is desirable.
    • A Review of the Dunmore East Herring Fishery (1962-1968)

      Molloy, J (Department of Agriculture and Fisheries (Fisheries Division), 1969)
      The winter herring fishery off the south coast of Ireland, based on what is commonly called the Dunmore stock, has been studied in detail by earlier workers and particularly by Bracken and Burd (1965). In their paper, they reviewed the fishery up to 1963 and arrived at conclusions regarding the economic yield of the fishery. They stated that, “ with the major spawning grounds (where the intense fishery takes place) situated within Irish exclusive fishery limits, there is considerable scope for the control of effort in such a way that, for the first time, a herring stock might be rationally exploited”. Since 1963, certain changes have taken place in respect of the stocks themselves and the fishing to which they are subjected. The purpose of this paper is to bring these changes to light and to compare the state of the fishery during the seasons 1962/63 to 1967/68 with that during the period of Braken’s and Burd’s observations.
    • Age, Growth and Maturity of Irish lobsters

      Gibson, F A (Department of Agriculture and Fisheries (Fisheries Division), 1969)
      A completely satisfactory method of ageing lobstem has not been developed. Gibson (1967) attempted to age lobsters using the principles of the von Bertalanffy equation as suggested by Beverton and Holt (1957). In this case the only determinable parameters were L∞, K and the annual growth rate was calculated from the recapture of tagged lobsters which had been at liberty for a period of one year, during which time they had or had not moulted. The smooth curve produced from these data suggested that lobsters first come into the catch, in large numbers at the end of their fifth year and are fully recruited in the sixth year. In reaching this age, the rate at which lobsters grow does not appear to be consistent, and does not appear to be so throughout the life span.
    • Pelagic Eggs and Young Stages of Fishes Taken on the South Coast of Ireland in 1967

      Kennedy, M; Fitzmaurice, P (Department of Agriculture and Fisheries (Fisheries Division), 1969)
      Emes W. L. Halt was one of the pioneers of research on the spawning and early development of marine fishes, and collections of pelagic eggs and young stages of fishes made by him on the west coast of Ireland were the basis of some major contributions to the then young science of fisheries biology (HoIt 1891, 1893, 1899). Much more recently Fives (1967a) has worked on pelagic young stages of fishes taken in the plankton on the coasts of Galway and Clare. Collections of eggs and young stages of clupeoids have been made on, the south coast of Ireland in winter during the years 1960-1962 (Bud and Bracken, 1965; Bracken and Kennedy, 1967). Hitherto, however, no collections of eggs or young stages of other fishes appear to have been made on the south coast. As part of a programme of research by the Inland Fisheries Trust into the biology of the bass, Dicerntrarchus labrax (L.) in Irish waters, tow-netting for bass eggs was carried out at four centres on the southeast and south coasts of Ireland during the period April to June 1967. Pelagic eggs of a variety of species of fish, including bass, were obtained, as well as larvae, post-larvae and fry. The tow-netting was done close to shore and in estuaries-areas not as a rule sampled as extensively as the offshore waters where the major commercial fishes The results of the tow-nettings help, therefore, to fill in some of the gaps in existing data on the reproduction of fishes on the Irish coast.
    • Occurance of Eggs of Echiodon drummondi Thompson on the Coast of County Kerry

      Kennedy, M; Champ, T (Department of Agriculture and Fisheries (Fisheries Division), 1971)
      As part of a programme of research on the spawning of bass Dicentrarchus labrax (L), tow-netting for pelagic fish eggs has ben carried out on various parts of the Irish coast during the years 1967 to 1971 inclusive. In May, 1970, in the course of tow-netting in Blasket Sound, Co. Kerry, eggs of the pearlfish Echiodon drummondi Thompson were taken in three hauls. Most of the eggs were hatched out and the larvae reared for some days. This appears to be the first record of the eggs of this species on the Irish coast. The following discusses the natural history of pearlfishes and the hauls in which pearlfish eggs were obtained.
    • The Whiting Fishery Off Counties Dublin and Louth On the East Coast of Ireland: Research Vessel Investigations

      Hillis, J P (Department of Agriculture and Fisheries (Fisheries Division), 1971)
      The stock of whiting (Merlangius merlangus L.) off Counties Dublin and Louth forms the basis of a commercial fishery (Hillis, 1968). This paper presents the result of research vessel investigations into the stock from July, 1962 to May, 1967. Hillis (1962, 1963) recorded the results from the early part of the period, which are also incorporated in the present work.
    • The Distribution and Abundance of Animals and Plants on the Rocky Shores of Bantry Bay

      Crapp, G B (Department of Agriculture and Fisheries (Fisheries Division), 1973)
      A survey of the rocky shores of Bantry Bay is described. This is intended to serve as a means by which future changes may be detected, as well as providing an account of a hitherto undescribed area of the Irish coast. The abundance of littoral animals and plants was assessed at regular vertical intervals on forty transects, and the distribution patterns of these species are described and discussed in relation to two major environmental variables, emersion and exposure to wave action. The method adopted may be suitable as a standard method for surveying rocky shores, and this is discussed in relation to the objectives of the survey.
    • Pelagic Eggs of Fishes taken on the Irish Coast

      Kennedy, M; Fitzmaurice, P; Champ, T (Department of Agriculture and Fisheries (Fisheries Division), 1973)
      During the years 1967 to 1971 inclusive, tow-netting for pelagic fish eggs was carried out at 13 stations on the east, south and west coasts of Ireland. Sampling was limited to the period late April to mid-June. Sampling stations included estuaries, bays and the open coast. A total of 16,902 identified eggs was taken, belonging to 27 species or groups. This paper discusses the eggs identified and the conditions under which they were found.
    • The Marine Algal Flora of Bantry Bay, Co. Cork

      Guiry, M D (Department of Agriculture and Fisheries (Fisheries Division), 1973)
      A documentation of the marine algal flora of Bantry Bay, incorporating distributional, ecological and systematic data, is presented with a view to establishing distribution patterns, and so that an indication of the species diversity of selected shores might be available in the event of major environmental change in the future. Qualitative investigations, chiefly in the littoral zone, were carried out at eleven sites in the inner part of Bantry Bay during 1969-1972. The resulting list contains a total of 166 species, of which 88 are new records for the Bay and 7 are new records for County Cork. The sites at which each species was found are enumerated, together with grid references, brief descriptions of the topography, and notes on the algal communities.
    • A diving study on Dublin Bay prawns Nephrops norvegicus (L) and their burrows off the east coast of Ireland

      Hillis, J P (Department of Agriculture and Fisheries (Fisheries Division), 1974)
      During 1971 a team of divers studied the structure and numbers of entrances of burrows of Nephrops norvegicus in the Irish Sea off Clogherhead and counted their numbers in plots of 28sq.m area. Numbers of entrances found ranged from one to six with a peak at 3 and the densities of Nephrops norvegicus found ranged from 1 per 2.5sq.m downwards.
    • Size Distribution and Food of Thornback Rays (Raja clavata L) Caught on Rod and Line on the Mayo Coast

      Fitzmaurice, P (Department of Agriculture and Fisheries (Fisheries Division), 1974)
      A total of 732 Thornback Rays (R. clavata) were examined for length, wingspan, weight, sex and food in two bays on the west coast of Ireland. The samples were taken by rod and line during angling festivals in Clew Bay in June 1971 and in Broadhaven Bay in September 1971. The length/wingspan relationship for both sexes in both areas was found to be linear and the wingspan/weight relationship was the same for both sexes. The males become mature between 15.0 and 17.0 inches (38 to 43 cm) wingspan, while the females become mature between 18.0 and 20.0 inches (45.5 to 50.5 cm) wingspan. The sex ratio of males to females in each of the two samples was 1:1 in Clew Bay and 1.4:1 in Broadhaven Bay. The main food items in the stomachs of the rays from Clew Bay were Macropipus spp. (44 per cent), Crangon (23 per cent), Carcinus (21 per cent) and Lamellibranchs (10 per cent). In Broadhavcn Bay Ammodytidae (21.5 per cent), other fishes (19.5 per cent) and Macropipus spp. (14 per cent) formed the bulk of food items. A total of 71 R. clavata were tagged in Broadhaven Bay in the summer of 1971 and to date there have been 8 recaptures 7 within Broadhaven Bay. The days at liberty varied from 0 to 775 and the greatest distance travelled was 14 miles.
    • Reproduction in Mytilus edulis L. (Mollusca: Bivalvia) in Carlingford Lough, Northern Ireland

      Wilson, J H; Seed, R (Department of Agriculture and Fisheries (Fisheries Division), 1974)
      The reproductive cycles of several Mytilus populations in Carlingford Lough were investigated between November 1968 and May 1971. The annual cycle varied slightly from population to population though spawning began simultaneously at all stations in the spring months when sea temperature was rising rapidly between 7.5° and 12°C. A secondary phase of gametogenesis during the summer months was confirmed by oocyte counts and the onset of the secondary spawning period occurred from 4-8 weeks after the initial spring emission. Although no significant differences were recorded in oocyte size in the different populations immediately before spawning oocyte densities were greatest at the seaward stations. Similarly, low shore populations had higher oocyte densities than those higher in the littoral zone where feeding time is severely curtailed. Size did not seem to influence gametogenesis nor did the severely polluted conditions prevailing in Belfast Lough. Seasonal changes in glycogen and lipid content of the mantle were studied in relation to the annual reproductive cycle. Primary settlement of early plantigrades on algae occurred principally in summer and winter. Secondary settlement on artificial substrates coincided with the disappearance of early plantigrades from the algae.
    • Field Observations on Larvae of the Dublin Bay Prawn Nephrops norvegicus (L.) in the Western Irish Sea

      Hillis, J P (Department of Agriculture and Fisheries (Fisheries Division), 1974)
      The occurrence of Nephrops norvegicus larvae in the western Irish Sea determined by survey cruises during 1969, 1970 and 1971 showed distribution patterns of the Irish coastal population which appeared to be, to some extent, separated from others adjacent (e.g. S.W. Manx), Vertical distribution showed the greatest numbers at 10-15 fm depth by day, ascending by approximately 5 fm around dusk; numbers deeper than 20 fm were very small except late in the season when they increased greatly. Differences between the Irish Sea and Faeroe, north~eastem English and Adriatic waters in larval season and rate of development were also found.
    • Laboratory Experiments on Pumping and Filtration in 'Mytilus edulis L.using Suspensions of Colloidal Graphite

      Wilson, J H; Seed, R (Department of Agriculture and Fisheries (Fisheries Division), 1974)
      Pumping and filtration of colloidal graphite and shell movements of Mytilus edulis from Carlingford Lough, Northern Ireland, were recorded in the laboratory. Pumping and filtration rates fluctuated widely even in undisturbed animals. Long term recordings demonstrated an inverse relationship between pumping rate and filtration efficiency. The effects of light, tidal cycle, particle concentration, temperature and salinity on pumping rate have been examined. Periods of light and dark did not affect pumping rate nor was there evidence for any intrinsic tidal rhythm in feeding. Pumping increased to a maximum at graphite concentrations of 20-25 mg/l. The rate prior to the addition of graphite influenced the response at certain particle concentrations. Filtration was most efficient at 18.5°C and decreased above 22.5°. Pumping steadily increased to a maximum at 22.5°. Filtration of acclimated mussels was maximal at 25-34‰ whilst feeding ceased at the extreme salinities of 15 and 50‰.
    • Captive rearing of larvae of the Dublin Bay prawn Nephrops norvegicus (L)

      Hillis, J P (Department of Agriculture and Fisheries (Fisheries Division), 1975)
      Wild caught Nephrops larvae were maintained in aquaria for as long as possible, in 1969, 1970 and 1971 together with a few which were hatched in the laboratory in 1971. Experiments were conducted at temperature ranges of 16°0 to 22°C and 11°C to 13 °C; the latter range is close to the ambient temperature of larvae in the sea. Direct observations, were obtained of the duration of all stages from first larval to third post larval (six successive stages in all), though percentage survival rates were rather low in some groups.
    • The growth of Mytilus edulis from Carlingford Lough

      Wilson, J H (Department of Fisheries, 1977)
      The growth of Mytilus edulis at five stations in Carlingford Lough and two in Belfast Lough was calculated from annually produced growth rings. These rings were shown to be annual from measurements of the seasonal growth of marked animals on the shore. Shell tissue ratios were found to vary from station to station. Variations in growth are discussed in relation to sea temperatures, breeding cycles, salinity, pollution and level on the shore.