The 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).

Marine Institute Annual Report for 2008

Salmonids farmed in Ireland in 2002 can be divided into the following groups: one year class of rainbow trout Oncorhynchus mykiss and three year classes of Atlantic salmon Salmo safar. The year classes of salmon include, smolts (2002 generation), one sea-winter salmon (2001 generation) and two sea-winter salmon (2000 generation). S1/2' s are fish which are transferred to sea in Autumn/Winter of the same year that they are hatched. Their S1 siblings smoltify and are put to sea in early spring, some three to four months later. Salmon which are at sea for a year or longer in April are known as growers/one sea-winter and are treated separately from younger salmon (smolts) and rainbow trout. Those salmon that were put to sea in winter 200 I /spring 2002 are referred to as smolts, or 2002 year class fish. During the 2002 sampling period all four groups of farmed fish were examined. Two species of sea lice are found on cultured salmonids in Ireland, Caligus elongates Nordmann, a species of parasite that infests over eighty different types of marine fish, and Lepeophtheirus salmonis Krøyer, which infests only salmon and other salmonids. Sea lice are regarded as having the most commercially damaging effect on cultured salmon in the world with major economic losses to the fish farming community resulting per annum (Bristow and Berland, 1991; Jackson and Costello, 1991). They affect salmon in a variety of ways: mainIy by reducing fish growth, loss of scales which leaves the fish open to secondary infections (Wootten et aI., 1982) and damaging of fish which reduces marketability.

Dependence on a relatively small sample size is generally viewed as a big disadvantage for survey-based assessments. We propose an integrated catch-at-age model for research vessel data derived from multiple surveys, and illustrate its utility in estimating trends in North Sea plaice abundance and fishing mortality. Parameter estimates were obtained by Bayesian analysis, which allows for estimation of uncertainty in model parameters attributable to measurement error. Model results indicated constant fishing selectivity over the distribution area of the North Sea plaice stock, with decreased selectivity at older age. Whereas separate analyses of survey datasets suggested different biomass trends in the southeast than in the western and central North Sea, a combined analysis demonstrated that the observations in both subareas were compatible and that SSB has been increasing over the period 1996- 2005. The annual proportion of fish that dispersed in a northwesterly direction was estimated to increase from about 10% at age 2 to 33% at age 5 and older. We also found higher fishing mortality rates than reported in ICES assessments, which could be the consequence of inadequate specification of catchability-at-age in this study or underestimated fishing mortality by the conventional ICES assessment, which relies on official landings figures.

The 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.

The Magharees fishery (Brandon and Tralee Bays in south-west Ireland) is 495 sq.km in extent, the majority of this area ≤20 m in depth. Since 1981 it has been occupied by a directed spider crab fishery yielding in some years all of the national catch of Maja brachydactyla. Maximum recorded landings were 336 t in 1999 and effort has numbered up to 10,000 pots annually. Increasing fishing capacity and declining opportunities have accentuated fishing effort on spider crab. This paper describes a catch census undertaken in the fishing season of March to August inclusive, 2000–2007 and a mark–recapture experiment, 2005–2007. A method of ageing the adult moult by attributing a chronology to the rate of erosion of the claw on the dactyl is introduced. Males migrated longer distances, moved into the fishery on a wider trajectory and demonstrated greater wear on the claw than females. Recapture rate of males was twice that of females. The conduct of the fishery changed in its 26 years in existence. Landings became more concentrated in the earlier months of the year and the recent summer fishery was characterized by fewer male captures. Larger males were quickly removed and none >140 mm carapace length survived in the fishery longer than one year.

From the mid 1960s competition for Atlantic salmon intensified with the expansion of high seas fisheries in the marine sub-Arctic and drift-netting closer to home. Inshore commercial fishermen and freshwater anglers saw progressively more of the salmon stock being landed outside its river of origin which prompted some to seek an alternative game species. Sea trout, which have traditionally been a by-catch of the commercial salmon fishery and which game fishermen valued, were considered and various clubs and individuals (fishery owners and managers) addressed queries to the Department responsible for fisheries on the possibility of developing a sea trout run to supplement a declining salmon population. The majority of queries examined by this writer concerned the introduction of sea trout to parts of river systems outside their normal range. A review of sea trout distribution (Fahy, 1977) described their migratory limit inland and contained adequate information to assess the suitability of the majority of fresh water bodies for the fish. The Caragh (Glencar) catchment was more intriguing. There are now in existence many investigations on the inter-relationships of salmonid species in fresh water and on their interactions with their environment but there are few specific references to the suitability of catchments for particular species. This investigation examines a case in point.

In view of the high degree of toxicity (Smith 1968, Simpson 1968) of BP 1002, Gamlen Oil Spill Remover, Dasic Slickgone and other "detergents" used in Cornwall to combat pollution from Torrey Canyon oil, it was considered desirable to investigate the toxicity of a compound marketed as an oil dispersant under the brand name "Corexit 7664", claimed by the manufacturers to be non-toxic to marine fauna. It is produced by the Standard Oil Company of New Jersey and marketed in the U.K. by the Esso Petroleum Company. It is stated by the manufacturers to be a non-ionic surfactant, soluble in fresh water, 5% NaCL solution and isopropanol, and dispersible in fuel and crude oils. It contains no organic halides or heavy metals. The investigations reported in this paper were made in two experiments. In the first, the toxic effects of straight dilutions of Corexit in seawater were assessed. In the second, the toxicity of Corexit-dispersed crude oil was compared with that of crude oil alone, with an attempt to imitate conditions at low tide on a polluted beach. The first experiment was carried out in Bantry, Co. Cork, using material collected locally. The second experiment was carried out in the laboratory of the Fisheries Division, Department of Agriculture and Fisheries, and the material was collected at Sandycove, eight miles south of Dublin.

The American hard-shelled clam (Mercenaria mercenaria) is a valuable bivalve molluscan shellfish in the U.S.A, and Canada. This bivalve is somewhat like the cockle (familiar to most Irish people) or the palourde (Venerupis decussata) which is gathered on some parts of the Irish coast and exported to France. Unlike the cockle which lives in sand, or the palourde which is found mainly in coarse sand and shingle, the hard-shelled clam lives in sandy mud. Some years ago this clam established itself in Southampton Water, on the south coast of England. It is thought that this particular stock originated from live clams thrown overboard from an American liner. Due to the warming effect of the outflow from a large power station near Southampton, coupled with naturally occurring high sea-water temperatures in this area, the clams were able to breed and multiply. Normally the seawater temperatures around the coasts of Gt. Britain and Ireland are too low to permit the clams to multiply by natural breeding.

The term deepwater refers to fishing in waters greater than 400m depth. The main species taken in these deepwater fisheries are roundnose grenadier, black scabbard, orange roughy, greenland halibut, tusk and deepwater sharks. The fisheries take place in depths between 800m and 1200m on the slopes of the Porcupine Bank and in the Rockall Trough to the West of Ireland. France was the first country to take an interest in deepwater stocks in the late 1980s. Since then Spain, UK Norway, Faroes and Ireland have developed deepwater fisheries. On the slopes west of Donegal, Norwegian long-liners fish for ling and tusk on the shelf edge. On the slopes of the Porcupine Bank Spanish longliners and gillnetters fish for shark. Further out in the Atlantic trawlers from many countries fish the Mid-Atlantic Ridge and the Hatton Bank.