Production of molluscs and common problems

Transcription

1 Production of molluscs and common problems

2 Production of molluscs in the World In 2000, the World aquaculture production of molluscs was estimated at millions of metric tonnes by the FAO it represented 23.5% contribution to the global aquaculture production Top five cultivated mollusc species the Pacific oyster, Crassostrea gigas ( metric tons) the Japanese carpet shell, Ruditapes philippinarum (1 693 tmt) the Yesso scallop, Patinopecten yessoensis (1 132 tmt) the blue mussel, Mytilus edulis (458 tmt) and the blood cockle, Anadara granosa (319 tmt), a total of 42 mollusc species contributes to the production This production is still increasing

3 C. gigas P. yessoensis R. philippinarum M. edulis

4 Global production trends 12,000 10,000 8,000 6,000 GROWTH APR (%/year) Change (%) Pacific cupped oyster Japanese carpet shell Yesso scallop Blue mussel Total molluscs ,000 2, BLUE MUSSEL YESSO SCALLOP JAPANESE CARPET SHELL PACIFIC CUPPED OYSTER TOTAL MOLLUSCS FAO data, 2002

5 world aquaculture in 2000 TOTAL PRODUCTION BY WEIGHT TOTAL PRODUCTION BY VALUE 45,715,559 metric tons 56,466,981,900 US $ AQUATIC PLANTS AQUATIC PLANTS 9.9% 22.2% 23.5% FINFISH 50.4% MOLLUSCS OTHERS 0.8% 16.8% 16.6% FINFISH 55.9% MOLLUSCS CRUSTACEANS CRUSTACEANS 3.6% OTHERS 0.3% FAO data, 2002

6 High volume / Low value Photos Barbaroux

7 Abalone aquaculture: an illustration of growth rates in the sector Compared abalone fisheries and aquaculture (metric tonnes) (Gordon & Cook, 2001)

8 Fisheries and aquaculture Aquaculture contribution is continuously increasing Photos Barbaroux

9 Visages of mollusc aquaculture

10 Mollusc in the different environments FRESHWATER PRODUCTION BRACKISHWATER PRODUCTION MARICULTURE PRODUCTION Finfish 97.7% Crustaceans 1.7% Others 0.6% Finfish 42.7% Crustaceans 50.5% Molluscs 6.1% Plants 0.7% Finfish 8.7% Crustaceans 1.0% Molluscs 46.1% Plants 44.0% Others 0.2%

11 Prince Edward Island Main products are the Malpeque oysters and PEI mussels In 1990, the landed value of PEI molluscs was $7 million, in 2001, the figure grew to $34 million. Today, the shellfish industry contributes close to $70 million to the Island s economy and provides employment for more than 2,500 Islanders in rural and coastal communities In PEI, the shellfish aquaculture industry is largely based on the culture of blue mussels and the American oyster. Culture techniques for soft-shell clams are also being developed PEI is Canada s leading producer of cultured mussels. In fact, production from PEI leases account for in excess of 80% of the mussels produced in Canada. The majority of PEI s oysters come from the traditional fishery. PEI is second only to British Columbia in terms of oyster production

12 Common problems Mollusc aquaculture is primarily an aquaculture activity and therefore shares common problems with the finfish and crustacean aquaculture sectors; Although no specific problems as compared to finfish and crustacean aquaculture, relative importance of these problems may be specific to the mollusc aquaculture sector.

13 Importance of transfers: recorded transfers of C. gigas in the world Native C. gigas Introduced C. gigas (Data FAO DIAS)

14 Transfers and introductions: a baseline of mollusc aquaculture In many countries, mollusc aquaculture is traditionally based on wild stocks which frequently do not fulfil market demand because of poor market value of the products, over-fishing of the resource, environmental disorders or impact of diseases An answer to this has very often been the introduction of new species or transfers of new stocks cultural improvements and hatchery production increase the demand for transfers of live molluscs

15 genetic evidence of P. margaritifera transfers between atolls in French Polynesia HivaOa Marquises Archipelago Marquises Archipelago HivaOa Takaroa Tuamotu archipelago Gambier Islands Mangareva Mangareva Tuamotu, Gambier & Société Archipelagos Manuae Société archipelago II Maupihaa Société Archipelago I Manuae Maupihaa Takaroa 1981/ Figure Courtesy Dr P. Boudry

16 Impact of transfers: introduction of Bonamia ostreae to Europe Europe The introduction is believed to have occurred with transfers of flat oysters, Ostrea edulis stocks were moved from California to France and Spain; the French outbreak revealed the parasite in Europe California The origin of the disease remains unclear

17 Risk associated to transfers In the context of global mollusc aquaculture, transfers and introductions are highly significant and currently recognised as a major source of epizootics and mass mortality outbreaks Photos Barbaroux Production (mt) C. gigas C. angulata O. edulis Year

18 Other sources of hazard: unrelated water activities However, other sources of contamination may exist and are increasingly recognised as knowledge progresses introduction of MSX in Cape Breton Island believed to have been caused by ballast waters also suspected to have occurred elsewhere (Marteilia sp. in Florida?, Marteilioides in Darwin harbour?, Bonamia sp. in North Carolina?, etc )

19 Other sources of hazard: culture and farming Another cause underlying mass mortality outbreaks and diseases may be the farming and aquaculture activity itself bringing flat oysters, Ostrea edulis, from sub-tidal to inter-tidal zones for aquaculture purpose may have resulted in a passage of Marteilia maurini from mussels to oysters speciation refringens - maurini 18S ITS1

20 Management of diseases No vaccines, and treatments are difficult to apply molluscs do not produce antibodies treatments would impact the environment Photo courtesy of Dr DL Choi, NFRDI Pusan

21 Management of diseases No vaccines, and treatments difficult to apply Health management in impacted zones stock densities culture practices triploids, genetically selected stocks, resistant species

22 Management of diseases No vaccines, and treatments difficult to apply Health management in impacted zones In an area free of a disease, the key point is to avoid any introduction of infected stocks standards, guidelines and recommendations are provided at international, regional and national levels efforts have been made to improve diagnostic methods for diseases of molluscs however, transfers are not the unique route of disease introduction or emergence

23 Diagnostic methods Until recently, most of the descriptions of mollusc pathogens were based on structural and ultra-structural studies Traditionally, diagnostic of mollusc diseases is primarily achieved by means of histology These methods have strong limitations need for highly qualified personnel time consuming techniques specificity / sensitivity

24 Diagnostic methods Overcoming limitations of histology & TEM in diagnosis rapid, specific and reliable methods are needed genes of phylogenetic interest are targeted in DNA based assays because of the current need to clarify taxonomy new developments are expected in the future broadening the range of molecular methods identifying new targets validation and standardisation of new methods is needed Methods developed in the view of their application screening, presumptive and confirmatory methods methods corresponding to different levels of technological skills and equipment sentinel methods

25 Summary Mollusc production, world-wide 5 main species of economic interest highly dynamic sector of production Asia is the main region although important producing countries exist outside the region variety of culture systems Current problems most of current problems are shared with other sectors transfers and introductions as underlying cause of disease outbreaks health management for invertebrates is a challenge in open water systems zoning, monitoring and surveillance of important diseases is the corner stone of health management other control option may exist depending on the culture system