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IRELAND

by

P. Lyng
National Correspondent
Inland Fisheries Division
Department of Fisheries and Forestry - Leeson Lane - Dublin 2 - Ireland

I FISHERIES BIOLOGY AND MANAGEMENT

1.Salmonids
1.1Investigations were continued in the Corrib Catchment and was initiated in the Erriff with a view to quantifying the production level of salmon smolts. A base line survey of the Waterville Catchment was undertaken to quantify the juvenile holding capacity of the system. The principal spawning and nursery areas were identified and a physical development programme was formulated.
1.2Survey work on adult sea trout on the Currane system followed a similar pattern over the past six years. The age composition and the growth of the anglers catch was calculated and was related to climatic conditions. The climatic conditions favourable to sea trout production continued to decline in 1984 and the indicators are now at their lowest since records commenced in 1948.
1.3Census work on the survival from ova to adults both for wild and hatchery reared salmon and sea trout was continued in the Burrishoole system. The survival of salmon in 1984 was the lowest recorded since counting began in 1970. There was a marked increase in the run in 1985. Similar results were obtained for the Corrib system where a proportion of wild and hatchery reared smolts were microtagged and the returning adults were monitored in the estuarine traps and in the offshore nets.
1.4The coded wire tagging programme of smolts and juvenile salmon was continued in 1984 and 1985. Approximately 469,798 were tagged in the period under review. The results obtained are providing some worthwhile information on the exploitation of salmon at sea and in Irish coastal nets. The tagging is confined to hatchery reared smolts except in the River Corrib where a proportion of the run of wild smolts is tagged.
1.5The population of trout in a range of Irish lakes is being monitored on an annual basis by means of gill nets. A similar survey of trout stocks in the larger riverine catchments was undertaken with a view to defining a fisheries management programme based on results obtained from age composition growth and size range of trout present in the system.
1.6The fish population of a mountain tarn (Lough Tay, Co. Wicklow) is being investigated. Studies include brown trout (Salmo trutta) the minnow (Phoximus phoximus) and the three spined stickleback (Gasterosterus oculeatus). Age growth and feeding of the three species in the reservoir with a meagre food supply, exacerbated by fluctuations in water levels is being investigated.
2.Non salmonid fishes
2.1A study was undertaken on the meristic characters of the Killarney shad Alosa fallax Killarnensis. This sub species is thought to be a non migratory lacustrine form of the twaite shad Alosa fallax according to Regan (1925).
2.2An appraisal of the cyprinid community of the Leixlip reservoir Co. Dublin was carried out in 1984 and 1985. A report on the hybridisation among parent species consisting of bream, rudd and roach was published. A study of the growth and feeding behaviour of the population was completed at the end of 1985.
2.3A review of the data collected at the Electricity Supply Boards trap for young eels at Parteen Weir on the River Shannon over the past twelve years was completed. The results showed great variation between years in time of arrival, intensity of migration and in the sizes of eels migrating.
2.4Studies in progress since 1981 on an unexploited stock of yellow eels in a small bay have shown variations in population density and structure between trapping sites between months and between years. Variations between stations are associated with local differences in the abundance of the principal food species Asellus aquaticus.
3.Environmental Investigations
3.1Rivers which are the subject of arterial drainage are being investigated. A predrainage survey was carried out on the Monaghan Blackwater and recommendation on amelioration of the effects of drainage of the system was sent to the drainage authorities. This included revegetation of the banks, landscaping, location of berms in stream structures and fish stocking.
3.2Investigations were carried out to determine the effects of siltation on survival of ova some distance downstream of dredging operations and in areas where there was no dredging. The results showed that the mortality of ova was excessive in the downstream stretch when compared with an undredged section of the river.
3.3A survey was carried out in a number of trout streams to determine the gravel distribution selected for spawning by brown trout and the depths at which the ova are deposited. The sediment was categorised using the geometric mean diameter of the particles. Four distinct strata were identified. The majority of the ova were deposited between six and eighteen cm below the surface. Very few ova were found in the upper stratum or the lower stratum.
4.Genetic Studies
4.1An electrophoretic study of the population structure of Atlantic salmon in Irish rivers and of hatchery strains is in progress. An investigation into the genetic diversity between migratory and non migratory Salmo trutta within and between two adjacent river systems is in progress. Preliminary results indicate that there is interbreeding between anadromous and non migratory Salmo trutta in these systems.
4.2An investigation into the biology and stock assessment of crayfish Austropotamobuis was carried out in White Lake, Co. Westmeath and in a stream in Co. Wicklow.

II FISH CULTURE AND DISEASE

1.Fish Culture
1.1The investigations in progress to improve the survival of migratory trout Salmo trutta under hatchery conditions have given some worth while results (70% from egg to yearling). The resultant smolts upon release indicated that the rearing of migratory trout was uneconomic. Of the recaptures in their first year after release only one third showed sea growth in their scales, the remaining two thirds showed slower (estuarine type) growth which indicated they did not go to sea.
1.2At the Salmon Research Trust installations on the Burrishoole system in the two years under review survival from egg to yearling was high (75% average) (1984 and 1985).
1.3Recurrent low level furunculosis accounted for a mortality of 2.6% of the 1984 yearlings. It was noticed that the sea trout parr and introduced salmon parr were much less resistant to furunculosis than the line bred salmon parr.
2.Diseases - Diagnostic
Protozoan parasites caused some losses in young salmon in freshwater and also in salmon smolts in the sea. The parasites involved were mainly Costia and Trichodina. Infectious Pancreatic Necrosis occurred in fingerling rainbows 1984 and 1985. Vibriosis caused major losses in wild eels in 1984 at an estuarine location. In the very warm summer of 1984 there were losses due to sunburn in salmon held in sea cages. A new disease of farmed salmon was recognised in 1984 and also occurred in 1985. The disease involves the exocrine pancreas.
3.Research
3.1The investigation into Proliferative Kidney Disease was focussed on (i) experimental transmission of the disease at a range of temperatures and (ii) on the ultra structure of PK“X” from earliest detection through to full clinical disease, in order to characterise the parasite and if possible its development sequence and (iii) an immunological screening of infected tissues to try to detect the early infective stage of PK“X” which cannot be detected miscroscopically in 1–4 weeks.
3.2An investigation into Ichthyobodo infection in farmed salmonids with a view to establishing whether freshwater and salt water forms exist and the most effective method of treatment in both environments.
3.3The pathology of the high incidence of malignant squamous cell carcinoma found in rudd is being studied. The work will characterise the structure and ultrastructure of the disease, and investigate possible genetic viral environmental and chemical agents in the aetiology.

III FISH AND POLLUTED WATERS

1.1In accordance with the conditions laid down in the Local Government (Water Pollution) Act 1977 - Water Quality Management plans for 5 of the major catchments in the country have been produced and a further 5 are at the draft stage. The recreational and beneficial uses of water in relation to fisheries have been considered in some detail in these plans.
1.2The Fishery Authority plays an active role in the licensing of discharges to fish bearing waters and there were several successful prosectuions for the non compliance with conditions for consent to discharge. There were 111 fish kills reported in 1984. The majority of the fish kills occurred in the months of June and July during high temperatures and low water conditions. Discharges from agricultural effluents i.e. slurry, silage, and crop spraying accounted for the majority of the fish kills. The data for 1985 has not been analysed.
1.3There is concern about the change in trophic status of a number of lakes in the country and the programme of monitoring is on going. In two of the larger bodies of water Lough Sheelin and Lough Ennell corrective measures have succeeded in reverting the conditions from hypertrophic to an acceptable level of eutrophy.
1.4A considerable advance was made in 1985 on the calibration of satellite spectral data with chlorophyll a concentrations and transparency values in lake waters. The situation now permits a major examination of available satellite data for the period 1975–1983 in several of the large lakes ( 10 ha) in the country. A report was presented on the impact of newly commissioned sewage treatment plant on the water quality of receiving waters. The results obtained indicated there was a need for phosphate removal in a number of cases because there was evidence of eutrophication in a number of rivers examined. Algal growth was prolific at certain periods of the year and this resulted in deoxygenation particularly at night time. The conditions encountered was sufficient to kill or severely stress fish. The problem of eutrophication in rivers is of concern and it will receive further attention in 1986.
1.5Work was initiated on Acid rain at several sites in the country. A new coal burning station to produce electricity was put on stream in 1985 and some base line data was obtained to see if the emission from the station will result in any change in water quality both in the vicinity of the station and in the direction of the prevailing wind.
1.6The effects of peat silt on the fish population of the River Drish is being investigated. The study includes physico-chemical characteristics of the river upstream and downstream of the discharge and also the fish population biology and feeding of the fish species present.
1.7A questionaire survey was used to determine the frequency of occurrence, the extent and duration of slime growth in Irish rivers and the effects on fisheries. Major problems reported included the appearance and amenity value being adversely effected (86.4%) smell and deoxygenation (46.6%) and damage to fish stocks (37.9%). The severity of the effects was directly related to the length of outbreaks. The study investigated the viability of ova and fry, the population size and any difference in feeding in affected stretches and this was compared with a control stretch.

IV PRODUCTION STATISTICS

The only production statistics available are for eels. The figures for 1985 are not available.

Production in 1983 and 1984 were 95,149 kg and 88,177 kg respectively.

V BIBLIOGRAPHIC REFERENCES

  1. Browne, J. (1984) Population estimates of juvenile Salmonidae. Irish Fisheries Investigations A23,37–42.

  2. Browne, J. (1985) Contribution of reared fish to the national catch in Ireland. Atlantic Salmon Trust Workshop on Stock Enhancement. 31pp.

  3. Browne, J. and Gallagher, P. (1985) The relationship between annual Atlantic juvenile salmon population estimates and direct estimates of subsequent smolt runs (1980–84) in the Corrib system, Ireland. ICES CM 1985, M3.

  4. Cross, T.F. C.P.R. Mills and D.T. Quigley (1984) Tagging studies on the migratory behaviour of wild and reared sea trout Salmo trutta in Western Ireland. Salmonid Smoltification Workshop, University of Stirling, Scotland.

  5. Cross, T.F. An intensive electrophoretic survey of brown trout and sea trout in Western Ireland. Sea Trout Workshop, WWA/Atlantic Salmon Trust, 1984.

  6. Doyle, J. (1984) The development of rainbow trout farming in Ireland. Irish Fisheries Investigations A23, 72–76.

  7. Fahy, E. (1984) Have hatcheries a role in sea trout management? Fishery Leaflet No. 122: 12pp

  8. Fahy, E. (1984) Landings to the Killorglin Fishery, Co. Kerry 1869–1965. Salmon Net 17: 38–46.

  9. Fahy, E. (1984) The sea trout year 1983. Fishery Leaflet No. 123: 15pp

  10. Fahy, E. (1984) Sea trout and their exploitation by draft net from the Feale and Munster Blackwater Rivers, Southern Ireland Fisheries Bulletin (Dublin) 8: 8pp

  11. Fahy, E. (1984) Consequences of marine feeding on the growth of sea trout. Sea trout workshop Plas Menai, Wales October 1984.

  12. Fahy, E. and R. Rudd (1984) The use of weight-length relationships in sea trout stocks. Salmon and Trout Magazine 228: 56–63.

  13. Fahy, E. and W.P. Warren (1984) Long lived sea trout, sea-run ferox, Salmon and Trout Magazine 227: 72–75.

  14. Fahy, E. (1985) Protecting finnock as a sea trout conservation measure. Salmon and Trout Magazine 230: 66–69.

  15. Fahy, E. (1985) The sea trout year 1984 Fishery Leaflet No. 127: 14pp.

  16. Fahy, E. (1985) Fish kills in Ireland: an analysis of incidents in 1983 and 1984 Fishery Leaflet No. 128: 19pp

  17. Fahy, E. (1985) Cyclic fluctuations in the abundance of trout Salmo trutta L. Arch. Hydrobiol. Suppl: 70 (3): 404–428.

  18. Hudson, A.V. and Julian D. Reynolds (1984) Distribution of Irish intertidal Talitridae. Bull. Ir. Biogeog. Soc. 8: 63–77.

  19. McCarthy, D.T. (1984) The advese effects of channelisation and their amelioration. EIFAC Symposium on Habitat Modification and Freshwater Fisheries. Paper No. 16.

  20. McCarthy, D.T. (1984) The impact of arterial drainage on fish stocks in the Trimblestown River. Irish Fisheries Investigations A23,16–19.

  21. McCarthy, D.T. (1985) Interactions between seals and salmon drift net fisheries in the West of Ireland. Fishery Leaflet 126: 6pp (mimeo).

  22. Mills, C.P.R., D.T. Quigley and T.F. Cross*. Rearing and ranching of sea trout in the Burrishoole river system. Sea Trout Workshop, WWA/Atlantic Salmon Trust, 1984.

  23. Mills, C.P.R. The results of a questionnaire on sea trout Salmo trutta rearing techniques in Europe. ICES CM 1984 M: 2. 11pp.

  24. Moriarty, C. (1984) (ed.) Advances in Fish Biology in Ireland. Irish Fisheries Investigations A23,95pp.

  25. Moriarty, C. (1984) Stock enhancement in the Irish eel Anquilla anquilla fishery. EIFAC Technical Paper 42, Supplement 1, 50–58.

  26. Moriarty, C. (1984) Behaviour and exposure to bird predation of elvers Anquilla anquilla following mass release. Irish Naturalists' Journal 21, 220–221.

  27. Moriarty, C. (1985) Riverine migration of young eels Anquilla anquilla (L.) EIFAC Working Party on Eel, Perpignan, 1985, 26pp (mimeo).

  28. Moriarty, C. (1985) Observations on the eels of Meelick Bay, Lough Derg, 1981–1984. EIFAC Working Party on Eel, Perpignan, 1985, 14pp (mimeo).

  29. Moriarty, C. (1985) Report on elver immigration to 1985. EIFAC Working Party on Eel, Perpignan, 1985 12pp (mimeo).

  30. Mulrooney, M. and E. Fahy (1985) Hybridisation among three cyprinid species in a Co. Dublin Reservoir, Ir. Nat.J3.21 (11): 470–472.

  31. O'Keefe, C. and J.D. Reynolds (1983) The occurrence of crayfish diseases and their significance in Ireland. Freshwater Crayfish 5: 299–306.

  32. Piggins, D.J. and C.P.R. Mills Comparative aspects of the biology of wild and reared Atlantic salmon smolts. Aquaculture 49. 321–333.

  33. Piggins, D.J. Sea trout in the Burrishoole system. Sea Trout Workshop WWA/Atlantic Salmon Trust, 1984.

  34. Piggins, D.J. 1985 The silver eel runs of the Burrishoole river system: 1959–84. Numbers, weights, timing and sex ratios. ICES CM 1985 M: 2 12pp.

  35. Quigley, D.T.G. and Nolan, F. 1984 First record of Char, Salvelinus alpinus (L.) from Shannakeela Lake, Maam Cross, Co. Galway. Ir. Nat. J. 21, 235.

  36. Reynolds, Julian D., N. Gray and C. Hunter (1984) Final Report of the Sewage Fungus Research Group, TCD, submitted to the NBST and CSET.

  37. Reynolds, Julian D. and Christine Hunter (1985) Evaluation of the use of artificial substrates in sampling the invertebrate fauna of sewage fungus slimes in Irish rivers. Cerh. Internat. verein. Limnol. 22: 2239–2243.

  38. Twomey, E. (1985) Evaluation of promoting natural propagation versus restocking. Atlantic Salmon Trust Workshop on Stock Enhancement. 16pp. mimeo.

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