RSS 1.0Irish Fisheries Investigations Series A - Freshwater
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Irish Fisheries Investigations Series A - Freshwater
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Temperature and Oxygen Determinations in some Irish LakesInformation 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.
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The Crayfish Astacus pallipes of an Irish LakeThe 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.
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The Distribution of Irish Char (Salvelinus Alpinus)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.
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Irish Kelt Tagging ExperimentsSince the beginning of the century large numbers of salmon kelts have been tagged in Irish waters and the results have been given in a series of papers...a considerable number of kelts have been tagged since 1962 at a number of stations in Ireland and they form the basis of this paper.
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Irish Pike InvestigationsThe spawning of pike was studied in 1965 and 1966 in five large Irish limestone lakes-Loughs Sheelin, Ennell, Mask, Corrib and Arrow. The spawning period was found to be February to April. Spawning took place in shallow, sheltered situations where there was a carpet of dead or living vegetation on the bottom at a depth of 20 to 60 cm. Spawning took place by day, at a water temperature of at least 9-1O C, when lake levels were high or rising. Gill-net catches reached a peak during periods of spawning. Weather conditions in February and March were much milder in 1966 than in 1965, and spawning began about a month earlier than in 1965. The eggs of Irish pike are 2.7 to 3.0 cm in diameter. They are golden to honey coloured, with a great many minute oil-globules distributed through the yolk in numerous tiny clusters. The incubation period in the field is probably 8-14 days, and the newly hatched larva is 8.0-9.0 mm long. For the first 10 days or so, the larvae hang vertically from the vegetation by means of adhesive glands on the head. They then become free-swimming, and soon afterwards begin to feed. At this stage they measure 13.0-13.5 mm. Their first food consists of small cladocera and copepods. Later, they feed on larger cladocera, amphipods, isopods, young stages of aquatic insects, and fish fry.
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Aspects of the limnology of Lough Gur, Co. LimerickA survey of Lough Gur, a 76 ha lowland lake in Co, Limerick, was carried out between December 1988 and October 1989. The lake is a hardwater, eutrophic system with consistently elevated levels of total phosphorus. Large algal crops were produced in spring, dominated by the diatom Asterionella formosa Hass. and in the autumn, dominated by Chlamydomonas - type biflagellates. A large crop of the floating macrophyte, Ceratophyllum demersum L., persisted throughout the year. Asellus and Chironomid larvae were the principal invertbrates recorded. The fish stock was dominated by rudd, Scardinius erythrophthalmus L. In addition pike, Esox lucius L. and eel, Anguilla anguilla (L.) were encountered.
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Papers Presented to the 7th Session of the EIFAC Working Party on EelThe Seventh Session of the Working Party on Eel of the European Inland Fisheries Advisory Commission was held in the Royal Hospital, Killmainham, Dublin. A list of the peer-reviewed papers and abstracts of other presentations to the session are given below. -- I M Domingos: Fluctuation of glass eel migration in the Mondego estuary (Portugal) in 1988 and 1989. -- Daniel Guerault, Raymonde Lecomte-Finiger, Yves Desaunay, Sylvie Biagianti-Risbourg, Pierre Beillois and Patrick Grellier: Glass eel arrivals in the Vilaine estuary (Northern Bay of Biscay) in 1990: Demographic features and early life history. -- Jan G P Klein Breteler: Effect of provenance and density on growth and survival of glass eels Anguilla anguilla (L.) in mesocosm experiments. -- R. Lecomte-Finiger, S. Biagianti-Risbourg, Y. Desaunay, D. Guerault, B. Fourcault, S. Planes and A. Yahyaoui: Age at recruitment of A. anguilla glass-eels on the eastern Atlantic coast as inferred from otolith growth increments. -- P McGovern and T K McCarthy: Elver migration in the River Corrib system, western Ireland. -- Christopher Moriarty: Catches of Anguilla anguilla (L.) elver on the Atlantic coast of Europe 1989-1990. -- Maria Assuncao Santos and Michael Weber: Growth studies on monthly captured glass eels from the Rio Minho in two recirculation systems. -- Raymonde Lecomte-Finiger: Age and birth date of elvers collected in Moorea (French Polynesia) (poster). -- Lotti Ben Abdallah: Influence of some abiotic factors on the abundances of glass eel Anguilla anguilla (L.) in the estuary of the River Loire, France (abstract). -- C. Belpaire, H Van Driessche, F Y Gao and F Ollevier: Food and feeding activity of glass eel Anguilla anguilla (L.) stocked in earthen ponds. -- Maria Bninska and Marian Leopold: The effect of eel on fish stock composition in lakes- preliminary results. -- Rose M Callaghan and T Kieran McCarthy: Variations in population structure and growth rate of eels in the Dunkellin river system, western Ireland. -- J L Costa, P R Almeida, C Assis, F Moreira and M J Costa: A study of methods of estimating the size of eel populations in small streams. -- Christopher Moriarty: Management of the Corrib eel fishery, Ireland. -- I A Naismith and B Kights: The distribution, density and growth of the European eel Anguilla anguilla (L.) in the River Thames catchment. -- W Russell Poole, Julian D Reynolds and Christopher Moriarty: Age and growth of eel Anguilla anguilla (L.) in oligotrophic streams. -- R H Hadderingh, J W van der Stoep and J M P M Habraken: Deflecting eels from water inlets of power stations with light. -- K Holmgren, H Wickstrom and K Fredga: Growth of eel in a meoscale experiment. -- Aline Caillou, Christian Francisco, Raymonde Lecomte-Finiger and Jean-Marie Salmon: Lipofuscin used as an age indicator in the European eel Anguilla anguilla (L.). Comparison between lipopigment, fluorimetric measurements and otolithometric data (poster). -- Peer Doering, Jiirgen Ludwig and Gerhard Gmel: Prelimary results of otolith amalysis with eels of known age (abstract). -- Antoine Legault: A study of some selectivity factors in eel ladders (abstract). -- F - W Tesch: Insignificance of tidal currents for silver eel migration as studied by eel trac.kings and current measurements. -- F - W Tesch and U Niermann: Stock density of eel larvae Anguilla anguilla (L.) on the European continental slope, based on collections made between 1985 and 1989. -- Takakazu Ozawa, Futoshi Kakizoe, Osame Tabeta, Takashi Maeda and Yasutaka Yuwaki: Larval growth and drift of the Japanese eel Anguilla japonica estimated from leptocephali collections (abstract). -- W-N Tzeng and Y-C Tsai: Otolith microstructural growth patterns and daily age of the eel Anguilla japonica elvers from the estuaries of Taiwan (abstract). -- S Appelbaum and V Birkan: The effect of grading on the growth and distribution pattern in young eels Anguilla anguilla (L.) reared in recirculating systems. -- Inge Boiitius, Karl Otto Wahlstrom and Curt Gelin: Experimentally induced sexual maturity in farmed European eel Anguilla anguilla (L.). -- G. Golombo and G. Grandi: Further experiments in the effects of sex steroids on the gonad sex differentiation of European eel. -- Soeren Hendriksen: Production of eel in recirculation systems in Denmark 1985-1991. -- M Saroglia, C lando Ii, lingle and G Angle: Recent developments in eel farming in Italy. -- Reiner Knosche: An effective biofilter system for eel culture in closed recirculating systems. -- Hao-Ren Lin, Mei-Li Zhang, Lianxi Chen, Glen Van Der Kraak and R E Peter: Effects of sex steroids on gonadotropin synthesis and secretion as well as ovarian development in female Japanese silver eel Anguilla japonica (abstract). -- J Hoglund, J Andersson, H. Wickstrom and M Reizenstein: The distribution of Anguillicola in Sweden and its association with thermal discharge areas. -- J Bosnakovski, K Necev, K Apostolski and M Hristovski: Appearance of eel diseases in Ohrid Lake. Inge Boetius: Development of Anguillicola infestations in some Danish lakes and inlets (abstract).
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Feeding Relationships of trout salmo trutta L., Perch Perca fluviatilis L., and Roach Rutilus rutilus (L.) in Lough Sheelin, IrelandSamples of trout, perch and roach were collected by gill netting from eight sampling stations over the period February 1982 - March 1984 to assess competition for food between the three species. At each of the sampling stations quantitative collections of benthic invertebrates were taken in order to examine the relationship between feeding and food availibility. Results indicate a significant correlation in diet between trout and perch, little correlation in diet between trout and roach and moderate correlation between perch and roach. The most important competitive interaction between all three fish species is likely to be at their juvenile stage for a cladoceran diet.
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Ecological Changes over 30 Years caused by drainage of a salmonid stream, the Bunree RiverThe general ecology of two sites in the Bunree River, May catchment are described for 1990 and compared with the observations of Toner, O'Riordan and Twomey, (1965) at the same sites 30 years ago when parts of this catchment were subjected to arterial drainage. Differences observed are discussed with particular reference to salmonid populations.
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Ecological Changes over 21 Years Caused by Drainage of a salmonid stream, the Trimblestown RiverA site on the Trimblestown River (Boyne Catchment) studied by McCarthy (1977 and 1983), pre- and post-drainage (1968 to 1974), was re-examined by the author in 1989. Changes in the nature of the stream bed, in-stream and bank flora and fish stocks over the entire period (1968 to 1989) are reviewed. Data indicate a general ecological recovery of the site 17 years after drainage works.
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An Analysis of the Gravels used by Spawning Salmonids in IrelandSamples of gravel from 79 sites selected for spawning by Atlantic salmon, 9 selected by sea trout and 13 within spawning areas but known to be unused by spawning salmonids were analysed. For comparison reported data on 81 samples from sites used by Pacific salmon were similarly analysed. No significant difference was found between the range of gravel distributions used by salmon and that used by sea trout. It could not be proved that the sites unused by spawning fish were avoided because of excess coarseness or fineness. The range used by Pacific salmon was found to be wider than that used by Atlantic salmon. A separate analysis was made of the portion of gravel coarser than 4mm in diameter. From this a suitable mixture for use in rehabilitating disrupted spawning areas is proposed. A proposal is made that for spawning gravel analysis the 0scale where 0 = -1.log2 particle size be replaced by a 0 scale where the multiplication by -1 is omitted. Key words: Salmonids, spawning, gravel, site selection.
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The Currane, Co. Kerry, Sea Trout Fishery, 1980-1986An updated account of the unique Waterville sea trout stock is provided. The latest genetic work is reviewed and the vulnerability of these fish to introgression by other strains of trout is considered. Waterville sea trout are relatively long lived and the consequences of this fact are documented with data supplied by anglers over a period of six years. On average, Waterville sea trout are the largest in Ireland although bag sizes in the fishery are small. Alterations in the stock are monitored over seven years from 1980 using angler caught material. Back-calculations of lengths at various ages are supplied together with information on weight: length relationships. condition factors and sex ratios. The main influence on the age structure of the stock was the recruitment of post-smolt annually. Freshwater productivity could be explained by the influence of length of growing season but regulating factors in the saline environment were not identified. There was some agreement between indicators of recruitment in the Waterville and Burrishoole (Co. Mayo) fisheries. The relationship between B type increment - a crucial element of growth bringing parr to migratory dimensions - and growing season is investigated and various methods of expressing the B increment in quantitative terms are examined.
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The Distribution of the crayfish Austropotamobius pallipes (Lereboullet) in IrelandThe distribution of Austropotamobius pallipes, the only freshwater crayfish recorded from Ireland and presumed to be an old native, is described using some 300 records collected since 1976: the positive and negative loci from regularly sampled rivers and streams are used to provide a baseline from which any future changes in distribution can be monitored. Although absent from some regions, most notably the south-west (south of the Dingle-Dungarvan line) and north-west (County Donegal), crayfish are widely spread in the country principally in Carboniferous Limestone areas. The natural chemistry characteristics of the river and stream sites supporting crayfish had the following ranges: pH 7.2 - 8.4, alkalinity 34 - 356 mg/l and hardness 47 - 402 mg/l. Factors which might be important in influencing distribution of A. pallipes in Ireland, including pollution, predation and disease, are discussed.
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Age, Growth and Diet of the brown trout Salmo Trutta L. in the Roundwood Reservoir SystemFrom April to October 1983 monthly samples, totalling 343 trout, were taken from the two reservoirs at Roundwood, Co. Wicklow, using a range of gill nets. In 1984 an extensive electro-fishing programme was carried out in the Vartry River and three other feeder streams, in which 605 trout were obtained. The age data, determined from the scales, showed that there were six year classes in the South Lake and five in the North Lake. The fish from the river and feeder streams were less than 4 years old, 90% belonging to 0 + and 1 + age groups. Trout from the South Lake showed faster growth, attaining 28.7 cm at year 5, compared to 23.2 cm in the North Lake. Only six trout were over over five years old. Sexual maturity was reached during the third year. The dominant food organisms were trichopteran larvae and pupae (Limnephilus vittatus) molluscs (Potamopyrgus jenkinsi and Sphaerium corneum) and chironomid larvae (Endochironomus sp. and Tanytarsus sp.). The species composition of the fauna of both lakes was almost identical, but biomass was greater in the South Lake where the trout populations appeared to be numerically smaller. The high female to male ratios in the lakes, varying between 1.37 and 1.67 to 1 did not appear to be age related. In the Vartry River and other feeder streams the fish were young, immature and predominantly male. These fish contained many more ephemeropteran nymphs than the lake trout. The oligotrophic state of the lakes, combined with the fluctuations in water level make it unlikely that any steps can be taken to improve the sport fishery using the native trout. Development of a put and take fishery is recommended.
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The Effects of Drainage on the Trimblestown RiverThe effects of arterial drainage on the macro-invertebrates and flora of a salmon nursery stream are described. A section of the Trimblestown River, Co. Meath was sampled from 1968 to 1974. In drainage operations of this kind the substratum where insect life predominates is removed, also fish and salmonid ova and fry life is affected by mechanical disturbance. A Surber stream-bottom sampler covering an area of 1 square ft (O.093m2) was used to take 107 samples. Wet and dry weights of the fauna were determined. A survey of the aquatic flora, pre- and post-drainage is also described. The fauna and flora were seriously depleted after drainage but recovered rapidly both in numbers and biomass a year after drainage was completed. There was an increase in the growth of emergent vegetation after drainage. Filamentous algae and Chara sp. recolonised the bed of the river replacing two submerged species (Fontinalis sp and Rorippa nasturtium) which had been abundant prior to drainage.
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Studies on the Three-Spined Stickleback Gasterosteus aculeatus L. from an Upland Irish Reservoir SystemMonthly samples were taken using a small-meshed beach seine. A total of 1092 sticklebacks were captured, 725 fish were used to calculate the age distributions and 699 were examined for gut contents. The age data, determined from the otoliths, showed that there were four age classes present. The mean length of first year fish (O-Group fish) was 2.24cm, of second year fish (I-Group) 3.36 and 4.47cm and 5.72cm for II-Group and III-Group fish respectively. The breeding season was June-July. Sex ratios were similar in both lakes and did not differ significantly from 1 : 1. Sexual maturity was reached by all fish above 3cm. The smallest maturing virgin was 2.6cm in length. Egg diameters varied between 1.0 and 1.5mm. The diet was similar in the two lakes studied. In the North Lake Cladocera, chironomid larvae, copepods and molluscs dominated while in the South Lake Cladocera, copepods, chironomid larvae and surface insects were dominant. Sticklebacks were extremely scarce in the Vartry River and feeder streams entering both lakes and would not pose a threat to egg production by trout and minnow in these streams. The influence of sticklebacks is discussed in relation to other fish species.
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Studies on the Minnow Phoxinus Phoxinus (L.) from an Upland Irish Reservoir SystemThe paper deals with the population structure and biology of the minnow, Phoxinus phoxinus (L.), in the Roundwood Reservoir system. A total of 4,342 minnow were taken during the study period from three locations, 2,796 fish were used to calculate the age distributions and 3,013 were examined for gut contents. The age data, determined from the otoliths, showed that there are five age classes present. The mean length at the end of the first year (O-Group fish), was 3.41 cm, at the end of the second year (I-Group fish) it was 5.32 cm and 6.68 cm at the end of the third year (II-Group). Only thirteen minnow were found to be older than three years. The breeding season is later than normal and peaks in August and September. Sexual maturity is reached by the majority in their second year and all older fish are mature. Egg diameters were shown to be smaller than for fish from midland Irish waters. In the North and South Lakes the dominant food organisms were found to be chironomid and trichopteran larvae, molluscs and Cladocera. The diet of the fish from the Vartry River contained more ephemeropteran nymphs. Seasonal differences in the diet are noted. The influence of the minnow on the associated fish species is discussed. An account of the distribution of the minnow in Ireland is included as an Appendix.
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Studies of the Eel Anguila Anguila in Ireland No. 4. In the Munster Blackwater RiverYellow eels from estuarine and freshwater populations were sampled by fyke netting: in 1965 and 1966 2,221 specimens from the estuary and in 1972 and 1973 826 specimens from freshwater. It was the first extensive study of eels in an Irish river and the population was found to be more dense than that recorded in lakes. Growth in the estuary was relatively fast and spawning migration began at 9 years while in the freshwater growth was slower and migration began about four years later. One specimen of 36 years old was found and more than 17% of the freshwater sample were over 19 years. Eels of less than 40 cm fed largely on invertebrates whereas eels of 50 cm and over fed mainly on fish, cyprinids being taken to a much greater degree than salmonids. It was calculated that fyke netting of the unexploited fishery could yield a catch of 21 tonne of eels of over 50 em length in the lowland freshwater portion of the river.
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Review of the Irish Salmon IndustryFor centuries the salmon has been an important item of commerce in Ireland and in many parts of the country today it is still very important in the general economy of the people, who gain a living directly or indirectly from it. It is important from two points of view. It provides sport for the angler and it supports a commercial fishery. There are three other articles in this issue: II. SALMON OF THE RIVER SHANNON (1957 to 1962) - Eileen Twomey; III. THE EFFECTS OF ARTERIAL DRAINAGE WORKS ON THE SALMON STOCK OF A TRIBUTORY OF THE RIVER MOY - E.D. Toner, Ann O’Riordan & Eileen Twomey; IV. RECAPTURES OF IRISH TAGGED SALMON OFF GREENLAND - A.E.J. Went.
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A Comparitive Limnological Study of Two Irish Lakes (Lough Sillan, Co. Cavan and Lough Dan, Co. Wicklow).A comparative study of Lough Sillan (Co. Cavan) and Lough Dan (Co. Wicklow) revealed that these two Irish lakes differ markedly in their physicoRchemical and faunal characteristics. The possible causes of these observed dissimilarities are reviewed and discussed. Lough Sillan may be classified as moderately eutrophic while Lough Dan is both humic and oligotrophic.
