• The Herring Fisheries on the North-West and West Coasts 1970 and 1971

      Kennedy, T D (Department of Agriculture and Fisheries (Fisheries Division), 1971)
      The main herring fishery off the north-west coast continued to take place from October to February, although an increased quantity of herrings was also landed during the period March to September.
    • Temperature and Oxygen Determinations in some Irish Lakes

      Fitzmaurice, P. (Department of Agriculture and Fisheries [Fisheries Division], 1971)
      Information about temperature and dissolved oxygen profiles in Irish lakes has hitherto been lacking. During the period 1966 to 1969 data on temperature and dissolved oxygen content at various depths were determined for a number of Irish lakes. The results are summarised in this paper.
    • Lobster Trap Census, 1970

      Gibson, F A (Department of Agriculture and Fisheries (Fisheries Division), 1971)
      This leaflet continues the information given in Fishery Leaflets No. 11 and 23 concerning lobster traps in use around the Irish coasts. As in previous years the lobster catch figures supplied to the Fisheries Division by various collectors have been correlated with the fishing gear used by boats fishing off the 12 maritime counties. There was little change in 1970 in the preference of the fishermen for the different designs of fishing traps used.
    • The Herring Fisheries on the South and South-West Coasts 1970/71

      Molloy, J P (Department of Agriculture and Fisheries (Fisheries Division), 1971)
      The 1970/71 winter herring fishery off the south coast, based mainly at the ports of Dunmore East and Cobh, began in the week ending 14th November, 1970, and ended on the 4th February, 1971. Eighty boats, seven more than in the 1969/70 season, took part in the fishery and landed a total of 110,816 crans. The total landing, which was an increase of 13,880 crans on the quantity for the previous season, was the highest yet recorded. During the season landings were made on 63 days out of a possible 74. The weather, which prior to Christmas had been reasonably favourable, deteriorated during January and brought fishing to a standstill on a number of occasions. This factor, together with the disappearance of the shoals in early February, closed the fishing season earlier than in the previous four seasons. All herrings landed were auctioned at either Dunmore East or Cobh.
    • Studies on Dublin Bay Prawns (Nephrops norvegicus) in the Irish Sea

      Hillis, J P (Department of Agriculture and Fisheries (Fisheries Division), 1971)
      The fishery for Dublin Bay prawns (Nephrops norvegicus) is carried on in a number of areas around the coast of Ireland, but the bulk of the catch comes from the Irish Sea north of Dublin, where the greatest landings, excluding County Down, are at Skerries, It is of recent origin, having been negligible prior to 1955, since when it had risen with some fluctuations to nearly 18,000 cwt in Counties Dublin and Louth in 1968. In research on prawns, there is no known means of ageing the animals, which makes estimates of their mortality and growth rate difficult. Sampling is complicated by the fact that they make burrows in the sea bed, into which they retreat when conditions are not suitable, thus sometimes giving small catches on grounds where the population may be large. This activity is governed by light conditions and the strength of bottom currents. In addition, females carrying external eggs disappear from the catch soon after becoming buried, due to either burrowing or emigration - most research workers believe the former to be the case. Work carried out in 1968 included:- (i) a survey of the commercial catch to find the size of prawns marketed and of those discarded at sea in order to compare their sizes with those taken in former years and (ii) with the aid of the research vessel, Cú na Mara, a comparison of the numbers, average size and sex-ratio of prawns from different depths and at different times of day. The aim of this research programme is to ascertain the facts governing the reproduction, growth rates and economic yield of this important stock of prawns.
    • The Crayfish Astacus pallipes of an Irish Lake

      Moriarty, C. (Department of Agriculture and Fisheries [Fisheries Division], 1971)
      The population of a 30 hectare limestone lake was studied. The crayfish were most active from July to September. Females carrying eggs were present from November to June. Parameters describing the measurements of the stock available for trapping were determined.
    • The Distribution of Irish Char (Salvelinus Alpinus)

      Went, A. E. J. (Department of Agriculture and Fisheries [Fisheries Division], 1971)
      Char* (Salvelinus alpinus) are rare in most places in Ireland to-day but they were formerly more widespread and abundant. About twenty-five years ago the Fisheries Division of the Department of Agriculture and Fisheries started to offer rewards for char submitted for examination and this has had the result of providing specimens which would otherwise have been lost. Many of these specimens wcre taken on rod and line but in recent years considerable numbers have been obtained in connection with either the improvement schemes of the Inland Fisheries Trust, Inc. or investigations concerned with the effects of drainage operations on Lough Conn.
    • Eel Research in 1970

      Moriarty, C (Department of Agriculture and Fisheries (Fisheries Division), 1971)
      The summer of 1970 was the third in which a standard set of fyke nets was used to make a detailed study of the eel stocks in a particular lake. The lake chosen was Lough Key which lies on the Boyle River, a tributary near the source of the River Shannon. Miss Ann Fortune and Miss Christine Royle, zoology students, were employed on bursaries for the field and some of the laboratory work. The method of working has been described in previous Leaflets (Nos. 9 and 21). In brief it consists of fishing daily with a standard set of eight nets (sixteen traps with eight leaders arranged in line) which have a cod-end mesh size of 10 mm. The eels were measured, weighed and sexed and otoliths and stomachs were preserved for examination.
    • Fluctuations in the Characteristics in Irish Salmon

      Went, A. E .J.; Twomey, E. (Department of Agriculture and Fisheries [Fisheries Division], 1971)
      Fluctuations in the catches and stocks of fish are exceedingly important and have interested scientific workers for years. As far as the salmon is concerned it is known that great fluctuations occur not only in the number of fish entering the rivers from year to year but also in their character. This paper is an attempt to put on record certain changes, some of which have already been recorded in papers on Irish salmon published in a very wide range of journals.
    • 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.
    • Water Quality Investigations in the River Blackwater and River Martin, Co. Cork--1966-1969

      Toner, P. F.; O'Connell, C. (Department of Agriculture and Fisheries [Fisheries Division], 1971)
      Investigations in the period 1966 to 1969 showed that the bulk of the waste discharged to the Blackwater and Martin is of an organic nature and arises mainly from industries processing milk, sugar-beet and other foods and to a smaller extent from domestic sewage. Pollution, indicated by increases in the biochemical oxygen demand and suspended solids and depletion in dissolved oxygen, was detected below the towns of Rathmore and Mallow on the main Blackwater, Mitchelstown, on a tributary of the Blackwater, the R. Funcheon, and Rathduff on the R. Martin. Depletion of dissolved oxygen sufficiently large to constitute lethal conditions for fish and other aquatic life was recorded only at Mitchelstown and it appears that the high rates of reaeration operating in most cases prevented more widespread deoxygenation and also reduced the extent of diurnal variation. The concentrations of suspended solids recorded in polluted reaches were well below those which are directly injurious to fish but the accumulation of this material as sludge in slow flowing stretches below outfalls constitutes an extra demand on dissolved oxygen which in combination with the B.O.D. of the water may lead to lethal conditions. In the Funcheon, the presence of this material and of sewage fungus on the substratum invalidates the application of the standard theoretical method for predicting the variation of dissolved oxygen. The partial or complete elimination of the normal flora and invertebrate fauna from riffles below the main waste outfalls, and replacement of these by biocoenoses typical of slow flowing silted reaches were recorded in each area. The extent of such changes seemed to be related more to the intensity of sewage fungus growth on the substratum than directly to the chemical quality of the water. Complete elimination of fish was only recorded at Mitchelstown, the stretch affected being half a mile in length. Trout and coarse fish were present in all af the other polluted stretches investigated though in some of these young salmon were absent and trout very few in number. Trout appeared to make better growth in polluted than in unpolluted water, especially at Rathmore, and this is due in part to a greater food supply in the former reaches. Short surveys of the Blackwater estuary indicated that this reach may be slightly polluted. While the investigations indicated that severe pollution occurred in several reaches of the Blackwater and Martin, it was considered that the overall productivity of fish in the rivers was unlikely, at that stage, to have been adversely affected by such pollution.
    • Herring Investigations on the North-West and West Coasts 1971-1972

      Kennedy, T D (Department of Agriculture and Fisheries (Fisheries Division), 1972)
      Although the main herring fishery off the north-west coast in 1971/72 covered the period from October, 1971 to February, 1972, a substantial quantity of herrings was landed during the period March to September, 1971.
    • Value of fish and shellfish landings into leading Irish ports 1962-1971

      Gibson, F A (Department of Agriculture and Fisheries (Fisheries Division), 1972)
      Landings of seafish are recorded under three broad headings, namely, demersal fish, pelagic fish and shellfish. The term demersal is applied to fish which live the greater part of their lives at or relatively near the sea bed. Demersal fish include roundfish such as whiting, cod, haddock, pollock and hake; flatfish such as plaice, sole, dabs, flounder, and also commercially valuable shark type fish such as skate and ray. The term pelagic is applied to fish which live the greater part of their lives in the upper layers of water and includes herrings, sprats, pilchards and mackerel. Shellfish include crawfish, lobsters, Nephrops (Dublin Bay prawns), crabs, shrimps and prawns all of which are known collectively as cruatacea; and escallops, mussels, oysters, periwinkles and various clams, which are known collectively as molluscs. The annual statistics published by the Fisheries Division of the Department of Agriculture and Fisheries give landings (by value) of approximately the leading 36 ports around the Irish coast.
    • Lobster Trap Census 1971

      Gibson, F A (Department of Agriculture and Fisheries (Fisheries Division), 1972)
      This leaflet continues the information provided by Fisheries Leaflets 11, 23 and 26. There was little change in the types of Lobster fishing gear in use in 1971 compared with previous years.
    • Some Problems and Methods in Dublin Bay Prawn (Nephrops norvegicus) Research

      Hillis, J P (Department of Agriculture and Fisheries (Fisheries Division), 1972)
      Much is in the process of being learned about the Dublin Bay Prawn or Norway Lobster Nephrops norvegicus (referred to simply as the prawn hereafter) but compared with many other commercially fished species much still remains a mystery. This paper describes methods of examination of its biology and ecology designed to yield information on habits, movements and especially growth and death-rates, these being the two most important factors in the prosperity of the fishery.
    • A List of Scientific and Engineering Papers by Members of the Staff of the Fisheries Division of the Department of Agriculture and Fisheries 1950-1970

      Anon. (Department of Agriculture and Fisheries (Fisheries Division), 1972)
      The Fisheries Division of the Department of Agriculture and Fisheries conducts researches into many aspects of Irish fishes, fishing and fisheries and a considerable number of papers on a wide range of topics have been published over the years in a number of journals including special publications of the Department, namely Irish Fisheries Investigations Series A (Freshwater) and Series B (Marine) and Fishery Leaflets. The present leaflet gives details of papers published by members, or former members, of the Department’s staff since 1950, as a result of their official work or arising there from. In addition to the papers mentioned below members of the Department's staff have contributed to various international bodies other papers, which have not been published subsequently. The list does not, however, include papers prepared by members of the Department's staff, whilst on secondment to semi-state bodies. Some of the authors have now left the service of the Department and details are given as necessary in the following list, Details are also given of the joint authors who were never in the service of the Department.
    • Catch Effort and Size Distribution in the Irish Lobster Fishing Industry in 1969 and 1970

      Gibson, F A (Department of Agriculture and Fisheries (Fisheries Division), 1972)
      This leaflet continues the study of catch and effort in the Irish lobster fishery, commenced in 1968, which was the subject matter of Fishery Leaflet No. 14 (Gibson 1968), As before, the results set out in this Leaflet have been obtained mainly from information supplied by Irish lobster fishermen who kept log books of their catch and effort in 1969. The response by fishermen to the requests by the Department to keep and fill in log books was still not as satisfactory as was expected, with the result that once again less than twenty log books were returned which contained information of sufficient standard to be useful in calculating the relationship between fishing and effort. The recording of this data is essential for the proper management of the lobster fishery in Irish waters and it is unfortunate that more fishermen are not co-operating in the log book scheme which is designed to help them. Those fishermen who have taken part in the scheme have already freely acknowledged that the log books (which remain their own property) have proved invaluable to them in their fishing operations, Furthermore the reproduction of all the data supplied by fishermen in one Leaflet enables those interested to see the rate of catch made by each type of boat or fishing gear. This information enables fishermen to compare their fishing results with those of others and so perhaps helps them to choose alternative and more satisfactory means for the capture of lobsters. However, if this service is to be of most advantage to all fishermen, the numbers of fishermen filling in log books must be increased considerably. It is hoped that the annual publication of these records will encourage other fishermen to join the scheme thereby furthering everyone's knowledge of this important species in Irish waters.
    • Seasonal and Annual Catches of Lobsters, Crawfish, and Crabs 1961-1970

      Gibson, F A (Department of Agriculture and Fisheries (Fisheries Division), 1972)
      During the ten year period from 1961 to 1970 certain changes took place in the lobster, crawfish and crab fisheries of Ireland which are worth recording and provide valuable information about the seasonal pattern of fishing for those species.
    • Eel Research 1965-1971

      Moriarty, C (Department of Agriculture and Fisheries (Fisheries Division), 1972)
      The catch of eels for the Republic of Ireland is very low. It averages 125 tons a year, thus comparing unfavourably with such figures as 800 tons for Northern Ireland and 1,500 tons for Holland. Since 1965 experiments have been in progress to find out whether there is any possibility of increasing the production of this valuable fish. A detailed report of the investigations was completed in March 1972 and this leaflet gives a summary of the most important conclusions. The approach to the problem was to make a study of some aspects of the life of the eel, concentrating on lakes where commercial eel fishing was well established. In addition to this some fishing trials were made in the estuaries of rivers such as the Munster Blackwater and the Shannon where no large-scale eel fishing had ever taken place.
    • Shellfish Survey of Estuaries and Bays of West Cork

      Crowley, M (Department of Agriculture and Fisheries (Fisheries Division), 1972)
      A survey was carried out in the summer of 1971 in the estuaries and bays of West Cork, by biologists from the Department of Agriculture and Fisheries. The purposes of the survey were to: (1) determine the potential of this area for possible shellfish farming; (2) discover any existing beds of edible mussels or other commercial shellfish species; and (3) describe the type of mussel found in each area.