Now showing items 21-40 of 49

    • National Survey of Sea lice (L. salmonis Krøyer and C. elongatus Nordmann) on Fish Farms in Ireland – 2008

      O'Donohoe, P.; Kane, F.; Kelly, S.; Nixon, P.; Power, A.; Naughton, O.; Tully, D.; Jackson, D. (Marine Institute, 2009)
      This bulletin reports on the National Sea Lice Monitoring Programme carried out by the Marine Institute in 2008. Results presented in this report are mean ovigerous sea lice levels and mean mobile sea lice levels for Lepeophtheirus salmonis and Caligus elongatus
    • National Survey of Sea lice (L. salmonis Krøyer and C. elongatus Nordmann) on Fish Farms in Ireland – 2007

      O'Donohoe, P.; Kane, F.; Kelly, S.; Nixon, P.; Power, A.; Naughton, O.; Jackson, D. (Marine Institute, 2008)
      This bulletin reports on the National Sea Lice Monitoring Programme carried out by the Marine Institute in 2007. Results presented in this report are mean ovigerous sea lice levels and mean mobile sea lice levels for Lepeophtheirus salmonis and Caligus elongatus
    • National Survey of Sea lice (L. salmonis Krøyer and C. elongatus Nordmann) on Fish Farms in Ireland – 2006

      O'Donohoe, P.; Kane, F.; Kennedy, S.; Nixon, P.; Power, A.; Naughton, O.; Jackson, D. (Marine Institute, 2007)
      This bulletin reports on the National Sea Lice Monitoring Programme carried out by the Marine Institute in 2006. Results presented in this report are mean ovigerous sea lice levels and mean mobile sea lice levels for Lepeophtheirus salmonis and Caligus elongatus
    • National Survey of Sea Lice (Lepeophtheirus salmonis Krøyer and Caligus elongatus Nordmann) on Fish Farms in Ireland – 2005

      O'Donohoe, P.; Kane, F.; Kennedy, S.; Naughton, O.; Nixon, P.; Power, A.; Jackson, D. (Marine Institute, 2006)
      This bulletin reports on the National Sea Lice Monitoring Programme carried out by the Marine Institute in 2005. Results presented in this report are mean ovigerous sea lice levels and mean mobile sea lice levels for Lepeophtheirus salmonis and Caligus elongatus
    • National Survey of Sea Lice (Lepeophtheirus salmonis Krøyer and Caligus elongatus Nordmann) on Fish Farms in Ireland – 2004

      O'Donohoe, P.; Kennedy, S.; Kane, F.; Naughton, O.; Tierney, D.; Jackson, D. (Marine Institute, 2005)
      This bulletin reports on the National Sea Lice Monitoring Programme carried out by the Marine Institute in 2004. Results presented in this report are mean ovigerous sea lice levels and mean mobile sea lice levels for Lepeophtheirus salmonis and Caligus elongatus
    • Validation of Standard Weights and Raising Coefficients for Discard Estimation: Report of a Survey Aboard MFV Roisin Bairbre

      Smith, T.; Comerford, S.; Officer, R. (Marine Institute, 2007)
      This survey was carried out to verify the Marine Institute's discard sampling protocol and the standard weights and conversion factors used when calculating discard rates. The MFV Roisin Bairbre was chartered to fish as normal on the Aran Prawn Grounds using twin rig prawn gear. The entire bulk catch was weighed, as well as the entire retained catch, thereby getting an accurate rate of discarding for this trip, as well as accurate individual basket weights. Retained catch was also weighed by species prior to and after gutting, to check the raising factors used when changing gutted landings back to round. This survey showed that the rate of discarding for this trip was 62% of the total bulk catch. There was no significant difference between the measured bulk catch weighed and the estimated bulk catch derived from using the standard weights. This validates the standard weights used. There was no significant differences between the observed conversion factors (from gutted to whole weight) and those currently used routinely in weight conversions. A standard weight for big baskets of bulk catch on a fish directed trip of 34.5 kg, and 28kg for a Nephrops directed trip were achieved.
    • Activity patterns of some inshore fishing vessels in 2006-2007

      Fahy, E.; Fee, D.; O'Connor, S.; Smith, T. (Marine Institute, 2007)
      Observations of daily “absence-from-port” patterns and indications of gears used were carried out on 147 vessels ranging from 5 to 13 m overall length, between April 2006 and March 2007 at three ports in west, southwest and southern Ireland. The vessels numbered approximately 6% of the total national fleet and they were larger than the average length of boats observing a daily working “absence-from-port” pattern. Fishing gears belonged to one of five categories: shellfish dredges, nets, hook and line, pots and otter trawl. More than half of the vessels observed did not carry any indication of fishing gear; 46 % had evidence of using one gear and 3% showed signs of using two. Activity (absence) patterns were low, ranging between 14 and 42 % of week-days on which observations were made. The annual pattern of gear usage described by BIM in 1999 was not apparent in any of the three ports. Instead, the local availability of fishing opportunities was influential in deciding which methods predominated. In only one port was there a marked seasonal activity pattern. Visible signs of vessel registration were similar to the situation in 2002.
    • Evaluation of the Benefits to Sustainable Management of Seasonal Closure of the Greencastle Codling (Gadus morhua) Fishery

      Ó Cuaig, M.; Officer, R. (Marine Institute, 2007)
      The project examined whether the seasonal closure of the traditional cod fishing grounds off Greencastle, Co. Donegal, could be an effective alternative management measure. The project was instigated by the local fishing industry and operated in cooperation between industry, the Marine Institute and Bord Iascaigh Mhara. The main objectives of the project were to demonstrate the change in yield likely to result from seasonal closure, and, to determine the pattern of movement of cod from the Greencastle fishery. Each winter from 2003 to 2005 the fishery was closed by Statutory Instrument. This was achieved with the voluntary commitment of the local industry. During this period over 13,000 cod were tagged and released by Marine Institute and BIM staff working aboard chartered fishing vessels. The closure itself provided a significant conservation benefit. During 2000-2002 50% of the Irish catch weight of cod in Division VIa (> 60% by number) was taken in the winter. The closure will therefore have markedly reduced the fishing mortality on cod that would otherwise have occurred from 2003 to 2005. As the Greencastle codling fishery is a mixed whitefish fishery, any benefits flowing from the closure are likely to have extended to other whitefish stocks. Growth was extremely variable but averaged around 17 cm per annum for cod at liberty for extended periods. During the winter tagging surveys the repeated recapture of recently tagged cod on the grounds indicated the retention of cod on the grounds during winter. Tagged cod at liberty for extended periods were subsequently recaptured on, or near the Cape grounds. This strong fidelity towards the Cape grounds during winter coupled with high growth rates may mean that a short winter fishing season, with a delayed opening, may yield a similar total weight of codling than the traditional fishery but with the catch of a reduced number of cod. Such schemes may reduce current fishing mortality rates. However, the stock status of Division VIa cod is so poor that a complete closure of the fishery is warranted. It is recommended that continuation of the project be considered as a mechanism for maintaining a closure of most of the Irish fishery, whilst simultaneously improving the quality of data available for stock assessment.
    • Gutted to round-weight conversion factors for anglerfish (Lophius poscatorius and Lophius budegassa)

      Lordan, C.; Gerritsen, H.D. (Marine Institute, 2006)
      In response to a request from the Department of Communications Marine and Natural Resources and fishing industry, the conversion factors used to estimate round or live weights from gutted anglerfish were re-examined. A number of data sources was available from survey data, port sampling and observer trips. In some cases, the liver is left in place when the fish are gutted. For these landings a separate conversion factor is necessary. The conversion factors were found to be independent of fish size, however, some significant differences between the data sources were found. Significant differences between the conversion factors of the two species of anglerfish (Lophius piscatorius and L. budegassa) were also found. As commercial landings of anglerfish are not usually speciated, a generic conversion factor was estimated for Lophius spp. by combining the data for both species after weighting by the estimated proportions of the two species in the Irish landings. The resultant conversion factor for fully gutted fish is 1.23 and 1.17 when the liver is left in place; both estimates are lower than the current Irish factor of 1.28.
    • Some thick shelled whelk Buccinum undatum characteristics and fisheries in Ireland

      Fahy, E.; Grogan, S.; Byrne, J.; Carroll, J. (Marine Institute, 2006)
      Observations are presented on two whelk populations from the Cape grounds in Co. Donegal and the vicinity of Helvic Head Co. Waterford. Both co-exist with large populations of brown crab (Cancer pagurus) which is the likely explanation for their thick shells. In the south west Irish Sea (with which comparison is made) and in the Cape stocks, 83-88% of individuals were easily aged by reference to the operculum. Heavy calcification obscured structure in the case of Helvic animals and only 6% of these could be confidently aged. Helvic and south west Irish Sea whelk have similar L∞, but both Helvic and Cape whelk have more rapid early growth than in the Irish Sea. The density of whelk in the Helvic vicinity is insufficient to support a commercial fishery. The yield of whelk from other areas of the Celtic Sea is sporadic and slow to recover from exploitation. The Cape fishery shows signs of rapid depletion since most recent exploitation began there in 2003. The centrally situated sectors of the south west Irish Sea fishery are highly resilient and recover rapidly from heavy removals of biomass which can exceed 50% per annum. Maturation appears to take place at a lower size and age in the Irish Sea than in the other two whelk stocks and this is tentatively proposed as the explanation for their lower productivity.
    • The status of the inshore component of the northern brown crab Cancer pagurus fishery, assessed from a time series of LPUE constructed from historical sources

      Meredith, D.; Fahy, E. (Marine Institute, 2005)
      A 27 year LPUE series was compiled from daily landings and creel numbers fished, as reported by a processor and by personnel participating in the activities of a small inshore fleet at Malin Head, Co. Donegal. The fleet targeted brown crab in the late summer and autumn months and the series was compared with two other series of LPUE constructed from data obtained from two fleet sources fishing the same stock. The most significant event to have taken place since records commenced in the late 1970s was the introduction in the 1990s of a small vivier offshore crabbing fleet. Competition between the inshore and offshore components intensified and the inshore fleet responded by further capitalising and increasing its seaward range. Since the mid-1980s the number of boats in the Malin Head inshore fleet pursuing the autumn fishery halved while the total amount of gear increased by 29%. The number of pots set by a vessel in a day averaged 600 in 2004 but in 2000 the practice of fishing two sets of gear simultaneously became established. The vivier boats also moved inshore and the ranges of the two fleets now overlap. In the past 15 years there was a loss of between 37 and 57% LPUE, according to the data assembled in this work. Schaefer analyses carried out on the inshore Malin Head fleet’s results and extended to cover the estimated landings of the Donegal inshore fleet, indicate that maximum sustainable yield was almost reached and that the F0.1 point was exceeded by both fleets. Any additional increase in F is likely to further accelerate decline in LPUE. The stock is regarded as being close to over-fished in a regime without effective effort controls. The problems associated with managing a fishery of this kind are briefly discussed.
    • A preliminary account of fisheries for the surf clam Spisula solida (L) (Mactracea) in Ireland

      Fahy, E.; Carroll, J.; O'Toole, M.; Hickey, J. (Marine Institute, 2003)
      Surf clams from seven stocklets on the west and south coasts are examined to provide a preliminary account of the fishery in Ireland. Spisula solida is the species harvested in every case. Most of the material was collected by commercial (box or hydraulic) dredge. A quantitative account of a surf clam bed is based on sampling by Day grab in Waterford Harbour. Ageing was by external shell sculpture. A limited comparison of this method with ageing by internal shell structure confirmed the method was usable and the results are presented on this basis with, however, reservations on the reliability of the approach. S. solida in Ireland had Linf of c 43 cm. Material gathered in Clifden, Co Galway, had an Linf of 35 mm. The Clifden stocklet was heavily fished when the material was gathered and a low value for Linf is attributed to the Lee phenomenon. A growth curve is constructed for only one stocklet, that in Waterford Harbour. Growth was slower than for S. solida in the North Sea, a possible consequence of heavy fishing also. The clam bed in Waterford Harbour was a low elevation bank of coarse (Spisula) sand. The area of the bed had become reduced during the preceding year by the invasion of silt grades displaced by earthworks upstream; these were injected into the coarse material to form a perimeter of the clam patch. Within the bed, the highest biomass of S. solida was 600 g/sq.m. Representation of age frequencies within samples suggests that heavy spatfalls of S. solida occur at irregular intervals and this complicates the calculation of F values from a catch curve. A yield per recruit curve is prepared for the clam patch in Waterford Harbour.
    • A survey by hydraulic dredge of interstitial bivalves with commercial potential in Cill Chiaráin and Beirtreach buí Bays and along their connecting shoreline, Co Galway

      Fahy, E.; Carroll, J.; Browne, R.; Ní Rathaille, A.; Casburn, P.; Breathnach, S.; Norman, M.; Stokes, D. (Marine Institute, 2002)
      The shellfish co-operative, Comharchuman Sliogéisc Chonamara Teó (CSC) manages oyster and scallop in Beirtreach buí and Cill Chiaráin Bays, both of which are designated aquaculture areas. Cill Chiaráin is also a candidate Special Area of Conservation (cSAC). Various traditional fishing activities are carried on in the bays and CSC has rights to exploit clam species there. The work described here is a survey of interstitial clam species by hydraulic dredge between November 2001 and January 2002. Investigations were restricted from some of the upper bay areas where surface bivalve management was in progress. Much of the remaining areas within the Bays proved unsuitable for hydraulic dredging by virtue of the nature of the substratum. The exposed parts of the lower bays and the intervening coastline where the substratum was coarse sand (maërl or shell sand) were suitable for hydraulic dredging but bedrock and loose boulders often proved obstacles to towing. There was evidence of two assemblages of bivalves in the bays: one typified by Venus verrucosa, Venerupis senegalensis and Tapes rhomboides, all large and potentially valuable, occurred within maërl mixed with fine mud, the other whose most valuable components included Ensis arcuatus and Spisula solida, occurred in disintegrating maërl and in shell sand. The bivalve fauna in the two bays appeared to be typified by relatively high diversity and low biomass – which is accentuated by recent natural mortalities of Ensis arcuatus, a dominant species - and this is likely to prove a challenge to marketing; the Irish market typically exploits small numbers of clam species simultaneously. The terms of the licence under which CSC operates may provide opportunities to exploit clams within their designated area by means other than hydraulic dredging and these should be investigated. In view of the scientific values of the area and its status as a cSAC any plan to exploit its interstitial bivalves should be discussed with the relevant state agency.
    • Strategy for the development of the eel fishery in Ireland

      Moriarty, C. (Marine Institute, 1999)
      In the course of a reply to a Parliamentary Question on eel in February 1997, the Minister stated that ‘there is considerable potential for development of the fishery and an integrated development strategy plan is being formulated’. The Marine Institute and other bodies were asked by the Department of the Marine to prepare a submission. The material which follows is based on the author’s work as a biologist, first in the fisheries service of the Government and, subsequently in the Marine Institute.
    • A Benthic Survey of Inner Bantry Bay

      Neiland, S.; McMahon, T. (Marine Institute, 1999)
      In February 1993 sediment samples were collected from a total of 18 stations in Bantry Harbour, Glengarriff Harbour and along the north shore of Whiddy Island. The samples were analysed for grain size, organic carbon content and the abundance of benthic infauna. The benthic infauna were identified to family level. The sediments in Bantry Harbour and Glengarriff Harbour were comprised of fine particles with typically >80% of the dry weight being in the silt/clay (<63 μm) fraction. In contrast, the sediments close to Whiddy Island contained relatively high amounts of coarser material. In Bantry Harbour a total of 53 families with 742 individuals were identified from the ten stations sampled. Of the 53 families identified, 21 were Polychaeta, 6 Bivalvia, 7 Gastropoda, 3 Echinodermata, and 16 Crustacea. A total of 31 families with 491 individuals were identified from the five stations sampled in the Glengarriff Harbour area. Of these 16 were Polychaeta, 4 were Bivalvia, 3 were Gastropoda, 1 was Echinodermata, and 7 were Crustacea. From the three stations sampled in the vicinity of Whiddy Island 47 families with 461 individuals were identified. Of these 23 were Polychaeta, 8 Bivalvia, 4 Gastropoda, 2 Echinodermata, and 10 Crustacea. In Bantry Harbour and Glengarriff Harbour cirratulid polychaetes were dominant and the benthic infaunal composition was indicative of stressed environmental conditions. In contrast, the sediments close to Whiddy Island exhibited a very healthy faunal composition with no one family predominating and high numbers of amphiuroid echinoderms were recorded from these sampling stations.
    • Aspects of the exploitation of hake Merluccius merluccius belonging to the northern stock by fleets based in Ireland

      Fahy, E.; Gleeson, P. (Department of the Marine, 1993)
      The development of the hake fishery in the ICES Divisions adjoining Ireland displays strong similarities to the fishery for megrim; Ireland's landings of hake rose from 100t per year in 1979 to 2,000t ten years later. Most hake comes from Divisions Vllg-k. The Communities Logbook of the Irish-Spanish joint venture fleet provides a short time series. CPUE by both demersal trawl and long line declined sharply between 1985 and 1991. The second quarter is the most productive of hake landings but otherwise there is no clear seasonal pattern. Hake were sampled on a half yearly basis and the fish were aged on the otoliths with a success rate of 70%. Ages in the first half were adjusted to a birth date of 1 January. Mean lengths at age were higher than those calculated by statistical methods (Normsep.). Length frequencies indicated two age groups in the discards. Methods of capturing hake have altered over the past five years, gill nets have increased their share of the Irish catch and, in 1991, were a close second to demersal trawl. Age of recruitment to the landings is 2-4 years. Discard hake was calculated at 25-163% by weight of landings per quarter in 1991, higher values coming from small-meshed nets targeting Nephrops. Survivorship curves based on aged length frequencies of hake taken by whitefish boats provided F values of between 0.40 and 0.76. These results are high and together with sharply declining CPUE would seem to suggest the part of the stock in Divisions Vllb-c and Vllg-k is more heavily fished than the stock in other parts of Sub-area VII.
    • A second assessment of the stock of megrim Lepiodorhombus whiffiagonis in Divisions Vll b, c, j and k

      Fahy, E.; Gleeson, P. (Department of the Marine, 1992)
      An assessment of megrim captured by Irish and joint venture (Spanish) vessels in Divisions Vll b, c, j, k is based on landings from both fleets and discards from Irish vessels targeting whitefish and Nephrops. Fishing activity by the joint venture fleet is centred on the 200m depth contour. Megrim CPUE has declined since 1985. Lepidorhombus whiffiagonis constitutes the majority of the landings by joint venture vessels; L. boscii amounts up to 2% by weight of the landings from deeper waters. In catches of undersized megrim, L. boscii was 12% of the total. Landings of L. whiffiagonis have similar length frequency distributions in the Irish inshore and joint venture fleets. There are indications of what may be seasonal abundance in the discards and landings of Irish vessels fishing inshore. Discards were calculated as 77% of landed weight in the first half of the year and 31% in the second. Megrim with an inshore provenance were slightly larger than those coming from deeper waters. The following growth parameters were calculated: L∞ = 51.2cm, k = 0.17 and to = -0.97. A catch curve derived from the combined landed and discarded megrim has a value of Z = 0.45, slightly less than the value calculated for the inshore Irish fleet (0.49). F is consequently in much the same position as in the 1989-90 assessment, on the negative slope of the yield per recruit curve.
    • Chemical contaminants in Irish estuarine and coastal waters, 1978 to 1988

      O'Sullivan, M. P.; Nixon, E. R.; McLaughlin, D.; O'Sullivan, M. L.; O'Sullivan, D. (Department of the Marine, 1991)
      Observations on the concentrations of heavy metals (mercury, cadmium, copper, lead and zinc) and chlorinated hydrocarbons (PCBs and the pesticides, lindane, dieldrin, DDTs and chlordanes) are presented. Sources comprise mussels and oysters from twenty six estuarine and coastal locations and in fin fish landed from all coasts. Data on heavy metals and nutrients in sea water and heavy metals in sediments for nine estuaries are also reported. Data were collected to comply with the Joint Monitoring Programme of the Oslo and Paris Commissions and with the Cooperative Monitoring Programme of the International Council for the Exploration of the Sea. The locations sampled included Boyne estuary, Dublin Bay, Wexford Harbour, Barrow estuary, Waterford Harbour, Cork Harbour, Bandon estuary, Tralee Bay, Shannon estuary, Clarinbridge, Kilkieran Bay, Clew Bay, Killary Harbour and Mulroy Bay. Four cases of elevated concentrations of cadmium, two each of copper, zinc and mercury and one of lead are reported. The general overall temporal trend in metal levels has been of stability or, in the case of more marked contamination, of reduction. The degree of organochlorine contamination was low in all the estuaries and shellfish growing areas monitored. No instances of contamination exceeding tolerance levels in shellfish and fin fish for human consumption were recorded. With very few exceptions, it was found that Irish coastal waters enjoyed exceptionally low levels of contamination.
    • Salmonid carrying capacity of streams in the Connemara region, a resource appraisal

      Fahy, E.; Nixon, J. J.; Murphy, M.; Dempster, S. (Department of Fisheries and Forestry, 1984)
      Standing crops of salmonids in the Connemara region are described from 80 site fishings made between March 1982 and May of the following year. Trout were more widely distributed than salmon, being able to exploit isolated water bodies as resident populations. High salmonid densities were associated with salmon which during the dry summer months were caught in large numbers on riffles. The smallest streams in the region supported only trout presumably because there was insufficient depth of water to permit the entry of salmon. Trout biomass and density within the region were distributed within the lower range reported from a number of countries in which brown trout are endemic and naturalised. Low saimonid densities at 16% of sites were in some cases associated with the rooting of angiosperms, and possibly oligotrophic conditions resulting from geological structure. Length at age of salmon and trout was similar to measurements recorded in Britain. The streams were important only for the first year of the trout life cycle. Because trout move downstream as they grow, occupying lakes during the later parr phase, and the entire streambed area in Connemara is one fortieth of the lake area, space is unlikely to be a critical constraint on the later parr phase. The condition of the stream substratum may be a factor in the production of sea trout; where loose gravels do not occur in shallow nursery streams, the catchments tend towards producing "brown" or "resident" rather than sea trout.
    • Sea trout and their exploitation by draft net from the Feale and Munster Blackwater Rivers, southern Ireland

      Fahy, E. (Department of Fisheries and Forestry, 1984)
      Biological characteristics of sea trout exploited in the rivers Bride (Co. Waterford) by angling and Feale (Co. Kerry) by draft net are described from small collections of scales and life data. Both stocks are short lived, poorly conditioned and have smolts whose fork lengths range between 19 and 26cm. Draft net fishing for these trout is conducted with relatively large meshed nets (4.45cm knot to knot). In the Feale highest catches are made in June and July and fish aged two sea summers constitute the majority of captures. A draft net mesh size smaller than the ordinary statutory minimum is required to retain large numbers of post-smoIt. A bunt mesh of 2.5cm knot to knot is effective in doing so.