• The exploitation of Grey Mullet Chelon labrosus (Risso) in the south east of Ireland

      Fahy, E (Department of Fisheries and Forestry, 1979)
      Fisheries for grey mullet are widespread on the south coast of Ireland, the majority being small and irregularly operated. The largest, at Wexford in the south-east, is a summer fishery where recent catches are well documented. At Wexford nets of mesh perimeter 18.4 cm are fished as fixed engines by two methods known locally as stake and ring nets. The fish are captured by wedging in a single mesh. Data from the stake nets give an indication of catch per unit effort and this has shown no significant variation from 1969 to 1977. From June to September 1977 fork length and girth measurements were made from 2,121 net-captured grey mullet; age and weight were determined for 528 of these. Gonads from 341 fish were weighed and 154 ovaries were sectioned. The majority of net-caught fish were between 31 and 45cm fork length and 8 to 12 years of age. As the season progressed the gonads of maturing males expanded up to 700% by weight. Growth of the ovary was variable and smaller in degree. Ovary weight in autumn correlated well with mean oocyte diameter. On the basis of previously reported growth data for grey mullet in British and Irish waters and on the length of fish retained by the nets a mean age of catch of 9.6 years is expected. This figure was approached only at the beginning of the season; thereafter the man age of capture was lower.
    • Observation on a bloom of Gyrodinium aureolum Hulbert on the south coast of Ireland, summer 1976, associated with mortalities of littoral and sub-littoral organisms

      Ottaway, B; Parker, M; McGrath, D; Crowley, M (Department of Fisheries and Forestry, 1979)
      In late July and early August 1976, kills of lugworm (Arenicola marina (L.)) and other marine life were reported from several areas of the south coast of Ireland. These reports were investigated and further field observations were made. The mortalities were associated with a bloom of the naked dinoflagellate Gyrodinium aureolum Hulbert. The possible origins of the bloom and its movement along the coast are discussed.
    • The cockle Cerastoderma edule (L.) on the South Bull, Dublin Bay: population parameters and fishery potential

      West, A B; Partridge, J K; Lovitt, A (Department of Fisheries and Forestry, 1979)
      The history of the Dublin Bay cockle fishery is reviewed briefly with emphasis on the period 1893-1913. Prior to 1900 some 80 tonnes of cockles are said to have been landed annually. In the subsequent decade the fishery declined and in recent times has been defunct. The population of cockles on the South Bull, Dublin Bay, was investigated in 1971 and 1972. Cockles were distributed throughout the beach, but occurred in greater density in the mid-shore region. The mean density, however, was low (9-13 cockles per sq.m) and the maximum recorded was only 51 per sq.m; this is consistent with the relatively exposed nature of the beach. The population was dominated by 0+ and 1+ age groups, though cockles as old as 9+ were collected. The age structure was consistent with regular annual recruitment, and the mean mortality figure for cockles in their second, third, fourth and fifth years was Z=0.76. The mean lengths at the end of the first four winters were 6.5, 22, 28.5 and 32 mm. The value of L∞ was 40 mm, and K = 0.6. The relationships between shell lengths and the weights of the shell, dry meat, wet meat, and shell + wet meat are described. The potential of this cockle population for commercial exploitation is considered, although in view of the low population density the catch per unit effort would probably be too small to be commercially viable at present. Yield curves indicate that a minimum legal length of 24 mm would be appropriate for protection of the breeding stock while allowing the optimum yield to be obtained. The potential sustained yield of the beach was estimated at 4 tonnes/sq.km annually at a fishing mortality of F=0.10.
    • Laboratory investigations into the absorption of dissolved free amino acids by the gill of the mussel Mytilus edulis L.

      Elliott, A J (Department of Fisheries and Forestry, 1979)
      Experiments were undertaken to investigate the uptake of dissolved free amino acids by the isolated gill of Mytilus edulis L., from concentrations approximating to those in sea water. Both neutral and basic amino acids were found to be absorbed against a concentration gradient and a proportion of each amino acid was incorporated in the tissue in ethanol-insoluble form. L-alanine was actively absorbed against a gradient by a process following Michaelis-Menten kinetics (Kt O.33mM, Vmax O.38μmoles/g dry wt/min) and was susceptible to metabolic inhibition. 14C D-alanine was absorbed against a concentration gradient and the label incorporated in the tissue in ethanol-insoluble form. The fate of the absorbed amino acids is considered in relation to efflux from and metabolism in the mussel. The significance of amino acid uptake is discussed with reference to their availability in the environment and their contribution to the nutrition of bivalves.
    • Benthic ecology of Dublin Bay in relation to sludge dumping: Fauna

      Walker, A J M; Rees, E I S (Department of Fisheries and Forestry, 1980)
      The Dublin Bay area in 1971 received sewage from about three quarters of a million people most of which was discharged or dumped off Howth to the north-east of the bay. Much sludge appeared to settle up and down the tide from the dump site, though finer particles entered the bay to the south. Additionally, dredge spoil was dumped south-east of the Baily up to 1971, but not in 1972. In 1971 and 1972 the effects of these organic wastes on the benthos were investigated. The fauna in the main part of the bay resembled the Acrocnida/Clymene community of Glémarec. On the sand banks there were also species of the Ophelia facies of Glémarec's deep Venus community. In the dumping area and in the southeast of the bay downtide of the dump site, where depths are greater, the faunas resembled the Nucula/Sabellaria community of Caspers. As well as having pollution indicator species, this latter community generally had greater faunal densities and diversities than elsewhere in the bay (except low divcrsities at the dump sites in 1971). Apart from a possible effect of depth, this suggests that the dumping was having an enriching rather than a degrading effect, although the probable sediment change since 1874 may imply a change in community type. Microvores (comprising surface-deposit and suspension feeders) were a prominent isotrophic group in the sampling area, and at the sludge-dumping site in 1971 particle feeders were abundant. All feeding types were more numerous in the organic waste settlement areas, though proportionally they appeared to be receiving differential benefits from the sludge and dredge spoil.
    • The rocky shore biology of Bantry Bay: a re-survey

      Baker, J M; Hiscock, S; Hiscock, K; Levell, D; Bishop, G; Precious, M; Collinson, R; Kingsbury, R; O'Sullivan, A J (Department of Fisheries and Forestry, 1981)
      A survey of the distribution and abundance of intertidal rocky shore animals and plants of Bantry Bay was carried out in 1970 and 1971 by G. B. Crapp and published in 1973. A re-survey was carried out during 1975 and early 1976 and a number of changes were noted. In an attempt to explain these the possible effects of changing weather conditions, the occurrence of oil spillages and the use of dispersants were examined. In most cases, the changes were not obviously attributable to visible oil pollution and seem more likely to result from a variety of natural factors. The re-survey highlighted a number of problems associated with this type of biological monitoring. The problems are discussed and some alternative approaches suggested.
    • Distribution and ecology of oysters, Ostrea edulis (L.) in Kilkieran and Bertraghboy Bays, Connemara, Co. Galway

      Barry, M D (Department of Agriculture and Fisheries (Fisheries Division), 1981)
      An account of Kilkieran and Bertraghboy Bay oysters is presented, including data on their distribution and ecology in these bays. Growth and population structure are compared with other oyster-producing areas in Ireland. These data are reviewed in relation to the feasibility of redeveloping such areas of former extensive oyster production.
    • The littoral fauna of Dublin Bay

      Wilson, J G (Department of Fisheries and Forestry, 1982)
      The intertidal sediment macrofauna of Dublin Bay was sampled over a total of 313 sites throughout the bay. The most conspicuous organisms were Nephthys caeca, Nephthys hombergi, Scoloplos armiger, Cerastoderma edule and Tellina tenuis, and in general, the fauna reflected the domination of the Bay by the sand habitats on the North and South Bulls. The standing stock of the Bay was dominated by the bivalves, which contributed over 80% of the biomass, and these in turn owed their supremacy largely to C. edule which accounted for over 80% of bivalve biomass. The bivalves were good indicators of the biotopes in the Bay: an outer sandy zone characterised by T. tenuis, and inner sand/mud zone with C. edule and Macoma balthica and muddy lagoons characterised by Scrobicularia plana and occasionally beds of Mytilus edulis. Bivalaves were absent from the inner Tolka basin where Nereis sp. predominated. Shannon-Weiner Index values for the Bay as a whole were good and there was little wide-spread indication of pollution damage.
    • The escallop, Pecten maximus (L.), in Killary Harbour

      Minchin, D; Mathers, N F (Department of Fisheries and Forestry, 1982)
      Escallops (843) collected by SCUBA diving ranged from one year to an estimated seventeen years old and varied in shell height from 17mm to 164mm. They were predominantly found on the slopes on either side of the Harbour at depths between 6m and 35m; very few specimens were observed on the soft mud in the centre of the Harbour. The density of escallops increased towards the mouth of the Harbour. The greatest numbers of specimens of less than 50mm were observed at the mouth of Killary. Variability in age frequency distributions along either side of the harbour could be explained by differences in settlement intensity from year to year. Settlement appeared to be more successful on the southern side than on the northern side. It also appeared that local dispersion from settlement areas occurred rather than active migration. Escallops four years old or less swam regularly while swimming was less frequently seen in individuals exceeding five years of age. It was concluded that Killary Harbour was unsuitable for the collection of spat but may be a suitable area for escallop cultivation.
    • Investigations in Bantry Bay following the Betelgeuse oil tanker disaster

      Grainger, R J R; Duggan, C; Minchin, D; O'Sullivan, D (Department of Fisheries and Forestry, 1984)
      About 30,000 tons of Arabian light crude oil plus some bunker oil was lost from the tanker Betelgeuse in Bantry Bay following an explosion and fire in January 1971. Most of the oil was burnt, and in the intense heat was polymerised into an asphalt-like material which coated the shoreline or sank, disrupting fishing activity. Oil leaked intermittently from the wreck for over a year during the salvage operation, and some of this was treated very effectively by spraying concentrated dispersant from an aircraft. Evidence of residual circulation suggested that the northern side of the inner Bay would have been most threatened by the dispersed oil. Several species of fish spawned in the Bay in the months following the disaster and larvae and post-larvae were not seriously affected. Fishing activity was disrupted but, apart from periwinkles Littorina littorea (L.), no commercial stocks were observed to suffer mortality as a result of the spillage. There was some very minor contamination of escallops Pecten maximus (L.) but this did not prevent escallop spatfalls in 1979 or 1980.
    • Seasonal changes in the intertidal fish and crustacean populations at Aughinish Island in the Shannon Estuary

      O'Sullivan, G (Department of Fisheries and Forestry, 1984)
      As part of a baseline study of the intertidal macrofauna of Aughinish Island, monthly samples of intertidal fish and crustacean populations were collected. A total of 13 fish and 7 crustacean species were identified. Of these shrimp Crangon crangon L., the mysids Neomysis integer Leach and Praunus flexosus (Müller) and the goby Pomatoschistus microps (Krøyer) were the most common and widespread species. Seasonal variation was apparent with low numbers in winter and spring increasing significantly in summer and autumn with the on-shore migration of adults and the recruitment of juveniles.
    • Temporal and Spatial Distribution of Ostrea edulis Larvae in Kilkieran Bay, Co. Galway

      Wilson, J H (Department of the Marine, 1987)
      Concentrations and size distributions of Ostrea edulis L larvae were recorded in Kilkieran Bay, Co. Galway, Ireland, during 1984 and 1985. Larvae were most abundant during July and August in both years. Large larvae ≥ 250 µm were homogeneously distributed through the vertical water column. Higher percentages of smaller larvae ≤ 250 µm were recorded at stations near the mouth of the bay than at stations on or near the beds. Variations in tidal amplitude and low salinities caused displacement of larvae from the beds. There were no significant losses of larvae from the inner bay.
    • The Distribution of Mytilus edulis and Anomid Larvae in Kilkieran Bay, Co. Galway

      Wilson, J H (Department of the Marine, 1987)
      The temporal and spatial distribution of Mytiius edulis and Anomiidae larvae were recorded in Kilkieran Bay, Co. Galway, during 1984 and 1985. Only larvae close to settlement (M. edulis larvae > 250 µm length and Anomiid larvae > 160 µm length) were considered. M. edulis larvae were commonest in late July, mid-August and early September 1984 and in early May, mid-June and early September 1985, while Anomiid larvae were commonest in late June and rnid-July 1984 and mid-June and early September 1985. M. edulis larvae were generally found in higher densities at the mouth of the bay, while Anomiids were more evenly dispersed, with high concentrations over the oyster beds. There was no significant (P < 0.05) net import of either species of larvae into the bay over tidal cycles.
    • The spurdog Squalus acanthias (L) fishery in south west Ireland

      Fahy, E (Department of the Marine, 1988)
      Spurdog landings are made on all parts of the Irish coastline but most heavily concentrated on the west of the country. The fishery expanded to a maximum catch of just under 8,000 tonnes in 1985. The species had been pursued most intensively in the north west but effort is shifting southwards. This account of the south west Ireland fishery is based on material collected between April 1987 and March 1988, inclusive; information was collected by questionnaire and 5,300 individual fish were examined. Ageing was undertaken using the posterior spine: ages in the commercial catches ranged between 5 and 40+ years. The growth characteristics of the south-west Ireland spurdogs resemble those of the Scottish-Norwegian fish, but the Irish populations have a lower L∞. Female maturation takes place at a shorter length than in other populations hitherto investigated from British or Irish waters; the length at 50% maturity is slightly more than 74cm which corresponds with an age of 14 years. The fecundity of the south west Ireland spurdogs is relatively high. Mortality coefficients (Z) of fully recruited spurdogs are calculated from age 17 as 0.24 for females and 0.30 for males. Two life tables are constructed. The first, which is intended to ascertain the numbers of female whelps required to maintain numbers, suggests that the stocks are close to being overfished. The second life table examines the age structure of the breeding female component of the population but its outcome is inconclusive. In terms of its organization the south west of Ireland spurdog fishery can be considered as two separate fisheries: a trawl and a gill net fishery, the latter being regarded as the more detrimental to the prospect of sustained yield.
    • Distribution of oyster Ostrea edulis, mussel Mytilus edulis and Anomiid larvae in Bertraghboy Bay, Co. Galway

      Wilson, J H (Department of the Marine, 1988)
      Concentrations and shell lengths of Mytilus edulis, Ostrea edulis and Anomiid larvae were recorded from April to October 1985 in Bertaghboy Bay, Co. Galway. The gamete volume fraction off eggs in female mussels was recorded in an introduced cultivated population of mussels in the inner bay during 1985. Oyster larvae were commonest in July and September, but were concentrated in the upper bay. Mussel and Anomiid distributions were more variable. While the commercial stocks of mussels in the bay contribute to the larval pool, this input is small in relation to that from other sources.
    • A Review and Catalogue of the Amphipoda (Crustacea) in Ireland

      Costello, M J; Holmes, J M C; McGrath, D; Myers, A A (Department of the Marine, 1989)
      The distribution and source of published and unpublished records of 307 marine, freshwater, terrestrial and subterranean amphipod species in Ireland are documented. A historical account of studies on amphipods in Ireland, including the researchers, frequency of publications, localities and habitats surveyed, and sampling methods, is presented. The occurrence of introduced species, commensalism, and parasitism is noted. The amphipod fauna recorded from Galway Bay, Kilkieran Bay, the Clare Island Survey, Belfast Lough, Strangford Lough, Dublin Bay, Carnsore Point, Cork Harbour, Kinsale Harbour, Lough Hyne and Valentia is discussed. The Irish and British lists are compared. Differences with the British list are largely explicable in terms of the latitudinal range of a species. The balance consists of rare, introduced, recently described, and unconfirmed records.
    • Fisheries for Ray (Batoidei) in Western statistical area viia, investigated through the commercial catches.

      Fahy, E (Department of the Marine, 1989)
      The status of the Irish Sea ray fishery is investigated using commercial catches of rays landed into two ports, Howth and Arklow. Approximately 80 45kg boxes were examined monthly over a year when approximately 100 individuals of each of the four contributing species were aged and measured. The species are R. naevus, montagui, clavata and brachyura. These are inter-mixed and casually segregated into four grades on their length. Weighting factors are provided to raise the sampled numbers to total landings. The frequency distribution of grades at the two ports is established from an analysis of some 5,700 commercial transactions. At Arklow, the pattern is stable from one year to another and apparently seasonal. Arklow boats have a short range. The pattern of landings at Howth is more complex; these vessels have a longer range and probably exploit various ages of rays. Growth in all four species occurs most actively during the summer months, slowing down in the winter. Annulus formation is not readily associated with the conventional birth date of 1 January. Coefficients of total mortality (Z) are high for the four species (0.38-1.00), higher than those found in a recent study of rays in Carmarthen Bay. R. brachyura is the most valuable species. R. naevus is the most numerous, possibly because it has a competitive advantage due to its age at full recruitment being one year later than those of the other three species. The yield of rays increases moving offshore and in a southerly direction in the Irish Sea. Landings into Irish ports by Irish vessels have increased between 1903 and 1985 although, until recently, ray as a percentage of total demersal landings was declining, from the 1950s.
    • The feeding relationships of the shanny, Lipophyrys pholis (L.) and Montagu's blenny, Coryphoblennius galerita (L.) (Teleostei:Blenniidae)

      O'Farrell, M M; Fives, J M (Department of the Marine, 1990)
      Collections of 279 specimens of Montagu's blenny, Coryphoblennius galerita (L.), and 276 shanny, Lipophrys pholis (L.), were made over a ten month period on a 2km stretch of the western shore of Mweenish Island on the west coast of Ireland. Further collections of 99 L. pholis and 8 C. galerita were made in March and April at two mainland sites. Sampling was confined to rockpools in the upper midshore region. The result of this bias was that while all age groups of C. galerita were collected, most of the L. pholis taken were less than two years old. Both species are omnivorous and exhibit definite seasonal feeding patterns. In general, C. galerita mutilate prey species, whereas only juvenile L. pholis are found to do this. Both species exploit a wide range of intertidal organisms. The ecological differentiation necessary for co-existence is evident, polychaetes are important only in the diet of juvenile C. galerita and bivalves and gastropods are important to L. pholis. There are only two food categories of importance to adult C. galerita and this may reflect the ecological stress on C. galerita of the habitat and the presence of L. pholis.
    • The post-peak-yield gill-net fishery for spurdog Squalus acanthias L. in Western Ireland

      Fahy, E; Gleeson, P (Department of the Marine, 1990)
      A gill net fishery, directed on Spurdog, expanded rapidly on the western coast of Ireland in the 1980s and quickly collapsed, the fishermen moving offshore in pursuit of smaller individuals. Catch per effort and landing data in the gill net fishery are used to estimate the size of the mature and maturing component of the south western "stock" which is within a range of 3,700 tonnes (landed) and 5,700 (calculated). An appraisal of the post-peak-yield landings reveals that the average individual weight declined from those of peak landings, in males by 9.5% and females 32.0%, and the percentage of females in them declined from 75 to 19%. The majority of the later catches were immatures whereas the peak-yield catches were mainly mature and maturing females. The average age of females was reduced from 19 to 16 years - 18 to 17 years in the case of males - and later captures were a shorter length at age. The fate of the depleted stock is not known and the possibility of its locus having moved elsewhere cannot be discounted.
    • The exploitation of megrim Lepidorhombus whiffiagonis by the Irish demersal fleet

      Fahy, E; Fannon, E (Department of the Marine, 1991)
      Two species of megrim occur in Irish waters but Lepidorhombus whiffiagonis constitutes the bulk of the catch by the Irish demersal fleet. Megrim is exploited as a by-catch of gadoid fisheries and is particularly associated with fisheries for Nephrops, angler and ray. Over the past 25 years megrim landings from the ICES divisions adjoining Ireland have fluctuated between 6,000 and 21,000 tonnes but there has been a gradual upward trend of which Ireland has taken an increasing share, rising to 1,800 tonnes in 1980. Spain exerts most influence in this fishery, being the location of the main market for megrim as well as having the greatest catching power. The most significant developments in the exploitation of megrim over the past twenty years are identified as the establishment of the European Exclusive Fishery Zone in 1977 and the entry of Spain to the Community in 1986. The importance of division Vlla as a producer of megrim has declined and the main fisheries for the species are in divisions VlIg-k. This assessment of the species is based on material gathered in 1989 and 1990 when length frequency data from the landings were collected from the west and south coasts. Lengths of approximately 8,000 megrim from landings from all divisions were collected in 1989, 28,000 the following year, and 1,400 were aged in the two years. Samples of the landings are comparable with graded exports from the fleet. The most intensive work was undertaken on a Nephrops and mixed whitefish fishery in Vllj. Megrim discards (round) are estimated to weigh 13.2% of landings (gutted). Few megrim of less than 20 cm were captured and no 0 group megrim was encountered. A growth curve is calculated for females and for females and males combined. For males the to value is outside the range of that parameter recorded elsewhere. Males are however a small proportion of the total, their higher mortality and slower growth giving them a skewed frequency distribution and reducing their contribution to the landings. Catch curves provided values for Z of 0.45 and 0.49 for females and combined sexes. Yield per recruit curves indicate exploitation is close to F max for females and on the negative slope for the sexes combined.