The geographical and temporal variations in the occurrence of DSP in Ireland are presented and the implications of the resulting closures on aquaculture operations and fisheries are discussed. Prior to 1992 DSP toxicity had been confined to the southwest and south coasts but in 1992 a protracted occurrence of DSP was recorded in Killary Harbour on the west coast

Doyle, J.

Jackson, D.

Nixon, E.

Silke, J.

Taaffe, B.

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International Council for theExploration of the SeaDublin, 1993C.M.1993/F:29Mariculture Committee••The Occurrence of DSP toxicity in IrelandD. Jackson, J. Silke, J. Doyle, E. Nixon and B. TaaffeFisheries Research Centre, Dept. of Marine, Abbotstown,Dublin 15, Ireland •AbstractThe geographical and temporal variations in theoccurrence of DSP in Ireland are presented and theimplications of the resulting closures on aquacultureoperations and fisheries are discussed. Prior to 1992 DSPtoxicity had been confined to the southwest and southcoasts butin 1992 a prot~acted oceurrence of DSP wasrecorded in Killary Harbour on the west coast.Introdu~tionThe Gymptoms of diarrhetic shellfish poisoning (DSP) weredeseribed in the Netherlands in 1961 (Kat, 1985). Throughthe seventies and into the eighties several moreoutbreaks were reeorded. By thc early eighties DSP hadbeen reeorded in a number of European eountries ineludingSpain (Fraga, 1987), Sweden (Underdal et a1, 1985),Franee (Mareaillou-Le Baut et a1, 1985) and Ireland(Dunne et a1, 1984).DSP eauses vomiting, abdominal pain and diarrhea. Thesymptoms usually clear within two days and there are nofatalities reeorded. In European waters the causativeagents are dinoflagellates of the genus Dinophysis. Cellcounts as low as 200 eells per litre have caused toxieityin shellfish (Lassus et a1,1985). Under EC direetive91/492/EEC shellfish for human consumption are requiredto be free of DSP toxins as determined by bioassay.Ireland has operated a DSP monitoring programme involvingboth phytoplankton monitoring and toxin monitoring sinee1984. Sinee it's ineeption there have been no eases ofDiarrhetic Shellfish Poisoning reported. Under thisprogramme the Fisheries Research Centre is responsiblefor monitoring and reporting results to both theDepartment of Health, who are responsible for regulatingdomestic consumption of shellfish, and the Fish QualityOfficers of the Department of Marine, who certify allexports.This paper deseribes the results of thatmonitoring programme to date and discusses the impact ofthe resulting closures on the shellfish industry.HethodsPhytoplankton sampIes were taken using a 1 litre Ruttnersampling bottle which was then subsampled. All sampIeswere preserved in lugols iodine for later identificationand enumeration using settling chambers and an invertedmicroscope.DSP toxicity was determined using the rat bioassay afterKat (1983). Confirmatory HPLC analyses were carried outto determine the precise nature of the toxins (Nixon andTaaffe, 1993).ResultsDSP toxicity in Ireland has resulted in the closure ofshellfish aquaculture areas since 1984 (Table. 1). From1987 to the present these closures have been an annualoccurrence, with some areas being closed almostcontinuously for periods of up to six months. The maineffects of these closures have been limited to an area ofthe southwest coast. This area cent red on Bantry Bay(Fig. 1) is aseries of southwest facing rias with anactive upwelling system and associated fronts (Raine eta1, 1990). The onset of toxicity is typically in Junewithin a matter of weeks of the appearance of Dinophysisspp. in the water (Jackson and Silke, 1993) and continuesuntil at least September. Toxicity has persisted untilthe end of November in some areas and regularly persists 4tinto the month of October.Details of the extent and duration of closures for thethree years 1990-1992 are given in Figure 2. In generalthe main closures have been in Kenmare, Bantry, Dunmanusand Roaringwater Bays. There have also been limitedclosures at sites on the south coast" including CorkHarbour. There was also a protracted closure of KillaryHarbour, Co. Galway in 1992. This is the first time DSPhas been detected on the west coast.Toxicity results to date in 1993 include closures in thesouthwest and Killary Harbour. Killary was closed due toDSP toxicity on 21/7/1993 and remains closed at the timeof going to press.DiscussionSince 1987 protracted closures of shellfish growing areashave occurred in the southwest with a resultant impact onthe aquaculture operations in the area. The almostcertainty of summer closures has forced local growers to "••concentrate on Autumn/Winter markets, giving them a verynarrow window of opportunity to seIl their crops. Whentoxicity persists into the autumn a portion of the cropmay be lost to autumn storms. Irish cultured musseIs aregrown in rope culture, with the ropes suspended eitherfrom rafts or longlines. The storms cause slippage of themusseIs on the heavily laden culture ropes and in severecases the majority of the crop on a longline can be lost.While it is difficult to quantify in economic terms theimpact of DSP on musseI culture in the southwest it iscertain that it does have a negative impact and in someyears this impact can be significant.The occurrence of toxicity in the Killary Harbour areafor two consecutive years is of some concern as it maypresage the spread of the DSP problem to the west coastwith the associated problems for shellfish aquaculture inthis region. Shellfish aquaculture in the west includesimportant native oyster (Ostrea edulis) growing areas asweIl as oyster, clam and scallop aquaculture operations.ReferencesDunne, T., Doyle, J. and Parker, M. 1984A review of the incidence and effects of unusual marineblooms in Irish coastal waters 1976-84.ICES special meeting on the Causes, Dynamics and Effectsof Exceptional Marine Blooms and related Events. ICES1984, D:9 4pp.Fraga,S. 1987Toxic dinoflagellate problems for musseI culturingindustry of Spain.In: The Problems of Toxie Dinoflagellate B100ms inAquaculture: Proceedings from a workshop andinternational conferenee held at sherkin Island MarineStation, Ireland, 8-13, June, 1987. Dale, B. et a1.Sherkin Island Marine Station, Sherkin Is. Co. Cork,1987.Jackson, D. and Silke, J. 1993Dinophysis species in Irish Waters.ICES CM/1993/L:30.Kat 1983Diarrhetic musseI poisoning in the Netherlands related tothe dinoflagellate Dinophysis acuminata.Antonie van Leeuwenhoek 49:417-427.Kat 1985Dinophysis aeuminata blooms the distinct cause of DutchmusseI poisoning.In: Toxie Dinoflagellates Anderson, D., White, A. andBaden, D. Eds. Elsevier, New York: 159-164.Marcaillou-Le Baut, C., Lucas, D. and Le Dean, L. 1985Dinophysis aeuminata Toxin: status of toxin bioassays inFrance.In: Toxie Dinoflagellates Anderson, D., White, A. andBaden, D. Eds. Elsevier, New York: 485-488.Nixon, E. and Taaffe, B. 1993DSP Toxins in Irish mussels and the contribution of a newtoxin DTX-2.ICES CM/1993/F:28.Lassus, P., Bardouil, M., Truquet, P., Le Baut, C. andPierre, M. 1985Dinophysis aeuminata distribution and toxicity along the •southern Brittany coast (France): Correlation withhydrological parameters.In: Toxie Dinoflagellates Anderson, D., White, A. andBaden, D. Eds. Elsevier, New York:159-164Raine, R., O'Mahony, J., McMahon, T. and Roden C. 1990Hydrography and Phytoplankton of waters off southwestIreland.Estuarine Coast. Har. Sei. 30:579-592.•Year Max. Toxicity Duration of Closures1984 August - Getober1985 01986 01987 3-4 August - Deeember1988 4 June - November1989 3-4 June - Septmeber1990 4 July - November1991 4 June - November1992 4 June - September1993 3 June -•Table 1 Incidence of DSP in Ireland"'.'.).l~loi·M':~ . '\ ,-~ ~;;,j..:~•.":r,,~:. ,"-Figure 1. Area of major annual DSP Closures•••Kenmu. (2 July-10 Sept)eantry (23 July-12 Nov)OUl1manus (30 July-12 No,,)S.,l.Figure 2a. Location of DSP Closures 1990·Kenm.r. (17 June-e Nov)gentry (10 June-28 NOv)----"r-.,..oF:::.;-'/Ounm.nus (24 June-24 Octl- -""";..'.Aoaringwater (10 June-1 Juty. 14 Ju1Y-29 July. 2e Auo-30 Sept)=;SCI'.Cork Mbr (,.5 Sept-30 Sept)t(lnul. (9 'ept-g Oct)Figura 2b. Location of DSP Closures 1991•Klllary 113 July-9 S.OI) ""'"L-.....~Kenmar. (29 June-19 AUQ. 26 Auo-9 Septaantry (22 Jun.-23 Sept)Ounmanu& (30 June-28 Aue) -,:r':""'"'"Roulngwate, (13 July-27 July). L. ~oyle (24 Auo-23 SooO11;.'.yougha. (20 Juty-2S AuO)Figura 2c. Location of DSP Closures 1992

The occurrence of DSP toxicity in Ireland

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The occurrence of DSP toxicity in Ireland

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