A long term study of bonamiosis in Quiberon bay, France

Transcription

1 lfremer A long term study of bonamiosis in Quiberon bay, France I. Arzul *, L. Miossec, E. Blanchet, C. Garcia, J.P. Joly, C. Francois and F. Berthe *Community Reference Laboratory for Mollusc Diseases - OIE reference laboratory for bonamiosis and marteiliosis- IFREMER La Tremblade FRANCE iarzul@ifremer.fr

2 Introduction The flat oyster Ostrea edulis was the flagship of the Breton oyster production until two diseases due to the protozoans Bonamia ostreae and Marteilia refringens spread in the 197 s. These diseases drastically reduced the flat oyster production from nearly 2, t per year in 197 to less than 2, t nowadays. Losses were estimated at about 2% of employment, 24 millions US$ of turn over and 2 millions US$ of added value between 198 and French flat oyster production (mt) Marteilia refringens Bonamia ostreae

3 Les Abers Rade de Brest Ile Tudy Morlaix Aven Etel Baie de Quiberon Introduction Binic Pénerf Cancale The protozoan Bonamia ostreae was first reported in June 1979, in oyster farms of Tudy Island, Brittany, in association with abnormal mass mortalities (8-9%) (Pichot et al., 1979). During the following months, the same parasite was detected in all the Brittany farming centres and then has rapidly spread to most European oyster stocks (both reared and wild). The introduction is believed to have occurred with transfers of flat oysters, Ostrea edulis moved from California to France and Spain.

4 Aims of the study To draw an updated and dynamic picture of the French flat oyster production from data collected during the national shellfish culture census carried out in 22 in France. To study the evolution of the disease in an endemic area (Quiberon Bay, Brittany) from pathological data collected between 198 and 24.

5 Flat oyster spat production (2): BREST 99.4% of spat is naturally collected on limed tiles or bags of mussel shells units are produced by 3 hatcheries in 2. All the Brest spat production and 1/3 of the Quiberon bay spat production is moved to Cancale, North Brittany, when spat is 1 months. CANCALE 12.2% 87.8% ε % units Bay of QUIBERON 21 data from national census (Agreste)

6 Flat oyster marketing (21): % NN BN BS PL PC A M CANCALE Bay of QUIBERON Marketing NB SB PL PC NN A Main production areas, including marketing Marketing areas tons M 21 data from national census (Agreste) Adult flat oyster transfer before marketing

7 French flat oyster production nowadays The French flat oyster production is located in few specialised areas: 2 spat collection areas: Brest and Quiberon bays 2 growth areas: Quiberon and Cancale 4 main marketing areas: Cancale, Belon, Golfe du Morbihan and Arcachon The French flat oyster production implies transfers: Spat is moved from Brest or Quiberon bays to Cancale for growth 83% of adults are moved from a farm to another before marketing

8 Quiberon study: material and methods About pathological data were collected in Quiberon Bay for different purposes with different sampling strategies on the period Diagnostic analysis were performed by tissue imprints (heart or gill) or less frequently by histology. Data were analysed by year, season and age and compared with some from other important production areas. Google earth (24)

9 Quiberon study: Results (1) Evolution of the detection frequencies/year (198-24),4,35,3,25,2,15,1,5, detection frequencies 24 nb indiv Detection frequencies Nb indiv

10 Quiberon study: Results (2) Evolution of the detection frequencies/season ( ),5,45,4,35,3,25,2,15,1,5 Winter Spring Summer Autumn Positive Total Detection frequencies,13,16,6,13 H P E A H P E A H P E A H P E A H P E A H P E A H P E A Detection frequencies Nb indiv

11 Quiberon study: Results (3) Evolution of the detection frequencies/age ( ),6,5,4,3,2, Spat Juveniles Adults 15 Nb spat Nb juveniles 1 Nb adults 5

12 ,4,35,3,25,2,15,1,5, Quiberon study: Discussion (1) Comparison with other production areas Cancale ,4,35,3,25,2,15,1,5, Quiberon Brest ,4,35,3,25,2,15,1,5, ,4,3,2,1, St Brieuc

13 25, 2, 15, 1, 5,, Quiberon study: Discussion (2) Potential impact of temperature and salinity? janv-87 janv-88 janv-89 janv-9 janv-91 janv-92 janv-93 janv-94 janv-95 janv-96 janv-97 janv-98 janv-99 janv- janv-1 janv-2 janv-3 janv-4 janv-87 janv-88 janv-89 janv-9 janv-91 janv-92 janv-93 janv-94 janv-95 janv-96 janv-97 janv-98 janv-99 janv- janv-1 janv-2 janv-3 janv-4,4,35,3,25,2,15,1 Temp Mean detection frequencies Nb indiv,5, , 38, 36, 34, 32, 3, 28, 26, 24, 22, 2, Rephy data Rephy data Salinity Mean

14 Quiberon study: Discussion (3) Larvae production and detection frequencies,4 detection frequencies Nb indiv 5,35 45,3 4 35,25 3,2 25,15 2,1 15 1,5 5, larvae number Men er Roué 6 Beaumer 4 Le Pô

15 Conclusions The history of bonamiosis in France highlights the risks related to transfers of live molluscs. However the French flat oyster production still relies on many transfers of spat and of adults before marketing. Bonamia ostreae is present in Quiberon Bay since 198 with prevalence usually lower than.15. Detection frequencies present fluctuations on the studied period and seasonal fluctuations within a year. The host-parasite system appears stable: since 25 years, Bonamia ostreae seems to have adapted itself to the flat oyster production, inducing less outbreaks than in the past. The flat oyster in endemic areas seems to have developed a relative natural tolerance to the parasite. Data are still needed to understand the evolution and distribution of the disease...

16 at io n ho riz ra ut ho ut ta ou ith w e in at se m is td no o Thanks for your attention Aknowledgements: Anne-Geneviève Martin & Aimé Langlade D