Cultural practices and risk of shellfish pathogen exchanges: the oyster aquaculture in France

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1 Cultural practices and risk of shellfish pathogen exchanges: the oyster aquaculture in France L. Miossec*, S. Girard**, N. Czerwinski* *Ifremer Département AGSAE, La Tremblade (France) **Ifremer Département Economie Maritime, Brest (France)

2 Introduction (1) Crassostrea gigas the main species of oysters in France and Europe Introduction of C. gigas at the beginning of the seventies Production (metric tons) Years C. angulata C. gigas Iridovirus Trends of the cupped oyster production in France (FAO, 2002)

3 Introduction (2) A national census concerning shellfish culture in France was carried out in 2002 The purposes were: to provide accurate information on the economical structure of the companies to analyse the cultural practices up to the market level to quantify the bivalve sales dedicated to consumption to measure the livestock transfers among rearing shellfish production areas

4 Objectives of this talk To present the results regarding Crassostrea gigas To discuss the potential consequences of these cultural practices (i.e. transfers) towards the introduction of exotic species including pathogens To highlight the necessity of these types of data In epidemiology

5 Methods Census realised by the statistics service of the French Ministry of Agriculture with collaboration of Ifremer and the National Shellfish-farming Committee Data collected between April and June 2002 Standardized questionnaire filled by trained investigators Data concerning shellfish farm activities in 2000 (spat production) and 2001 (other life stages - economical data) All the French shellfish farms* investigated * All farms rearing shellfish, including hatcheries and nurseries

6 VAAST 8.5% % North Normandy CANCALE ABER BREST ra ut Oyster production tons North Brittany ut ho 20% % ta 8.5% 355 8% Lease surface ha ith Bay of QUIBERON RÉ 31% % Aquitaine o no Bay of MARENNES td Poitou Charente is se m in at Bouin e Pays de Loire w Bay of BOURGNEUF D N oyster firms ou ÉTEL South Brittany % 251 8% at io n Ouest COTENTIN PAIMPOL MORLAIX Bay of VEYS ho riz Results (1) La Tremblade 7% 374 4% ARCACHON bay THAU Sète THAU lagoon lagoon Mediterraneen sea 9% 367 3%

7 Results (2) North Brittany 0.2 % South Brittany 22.8 % Poitou Charente 41.4 % ε % Aquitaine 35.6 % 1.4 ha 2 % Pays de Loire North-Normandy 28.9 ha 86.5 % 8.2 ha 11.5 % 2000 Mediterranean sea Natural spat production 3.8 x10 9 units 84% Hatchery spat production 0.7 x10 9 units 15%

8 % N-N NB SB PL PC A M Oyster production and marketing in the different French growing areas in 2001 Oyster production: tons Oyster marketing: tons Production Marketing N-N North Normandy NB North Brittany SB South Brittany PL Pays de Loire PC Poitou Charente A Aquitaine M Mediterraneen sea NB SB A N-N PL P C M

Results (5) The transfers of oysters for marketing Fattening : a speciality of Poitou Charente adding value to the final product Number of oyster farms (including non specialized) Exploited oyster

9 Results (5) The transfers of oysters for marketing Fattening : a speciality of Poitou Charente adding value to the final product Number of oyster farms (including non specialized) Exploited oyster surfaces in public maritime grounds (ha) Exploited oyster surfaces in wetland ponds called claires (ha) Oyster production (tonnes) Oyster sales dedicated to consumption (tonnes) including fattened oysters Poitou Charente % national 38% 22% 91% 31% 44% 88%

10 Other reasons for oyster transfers Regional specialisation The purchase (or supplying) of natural spat from enterprises located in non spat producing areas Productivity differential between rearing areas The purchase (or supplying) of half-grown oysters from enterprises seeking to optimize factors allocation (time-saving, cost-reducing.) Land use rights management When economic growth strategy relies on multi-localisation, transfers can occur several times

11 Results (4) % N-N NB SB PL PC A M Oyster transfers among oyster rearing areas at different developmental stages (receiving areas) in 2001 Spat half growing adult NB SB N-N North Normandy NB North Brittany SB South Brittany PL Pays de Loire PC Poitou Charente A Aquitaine M Mediterraneen sea A N-N PL P C M

12 Discussion (1) This census is the first exhaustive overview of the French oyster activity, showing some geographical specificities Movements between rearing areas are frequent and important along the rearing period (spat, half growing oyster and adult oyster) Main risk associated with shellfish movements inside a country from one shellfish areas to others: Introduction of exotic species and/or exotic pathogens

Discussion (2) Ocinebrellus inornatus first detection in 1995 Recent results demonstrated the major role of oyster importation as vectors of the exotic species Ocinebrellus inornatus (Martel et al,

13 Discussion (2) Ocinebrellus inornatus first detection in 1995 Recent results demonstrated the major role of oyster importation as vectors of the exotic species Ocinebrellus inornatus (Martel et al, 2004) from USA to France then its expansion along the French Atlantic coast due to cultural practices North Brittany South Brittany Poitou Charente Aquitaine North-Normandy Pays de Loire 1995 Ocinebrellus inornatus observations Mediterraneen sea

14 Discussion (3) 1993: 2 C. gigas infected by Haplosporidium nelsoni from 791 oysters analysed (from Renault et al., 2000) North Brittany South Brittany Poitou Charente Aquitaine North-Normandy Pays de Loire Mediterraneen sea Haplosporidium nelsoni detection

15 Conclusion Data on shellfish cultural practices are necessary to investigate epidemiological situation to discuss time series data on pathogen presence and disease status to define the zoning and the strategy when implementing a surveillance programme

16 Thank you for your attention Ifremer J-P Joly

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