Production of molluscsProduction of molluscsandand
common problemscommon problems
Production of molluscs in the World
In 2000, the World aquaculture production of molluscs was estimated at 10.73 millions of metric tonnes by the FAO
it represented 23.5% contribution to the global aquaculture production
Top five cultivated mollusc speciesthe Pacific oyster, Crassostrea gigas (3 944 042 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
C. gigasP. yessoensisR. philippinarumM. edulis
0
2,000
4,000
6,000
8,000
10,000
12,000
1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000
BLUE MUSSEL YESSO SCALLOP JAPANESE CARPET SHELLPACIFIC CUPPED OYSTER TOTAL MOLLUSCS
GROWTH APR (%/year) Change (%)70-80 80-90 90-00 70-00 99-00
Pacific cupped oyster +6.3 +4.0 +12.7 +7.6 +9.5Japanese carpet shell +22.2 +20.9 +18.3 +20.5 -9.4Yesso scallop +21.7 +23.7 +12.8 +19.3 +22.0Blue mussel +2.2 +0.4 +2.3 +1.6 -8.0Total molluscs +5.6 +7.0 +11.5 +8.0 +5.8
FAO data, 2002
Global production trends
world aquaculture in 2000
MOLLUSCS
OTHERS 0.8%
CRUSTACEANS
MOLLUSCS
FINFISH
55.9%
56,466,981,900 US $45,715,559 metric tons
FINFISH
CRUSTACEANS 3.6%OTHERS 0.3%
50.4%16.6%
16.8%22.2%
23.5%
TOTAL PRODUCTION BY WEIGHT TOTAL PRODUCTION BY VALUE
AQUATIC PLANTS AQUATIC PLANTS 9.9%
FAO data, 2002
High volume / Low value
Photos Barbaroux
Abalone aquaculture:an illustration of growth rates in the sector
0
2000
4000
6000
8000
10000
12000
14000
16000
1989 1999
Compared abalone fisheries and aquaculture (metric tonnes)(Gordon & Cook, 2001)
Fisheries and aquaculture
Aquaculture contribution is continuously increasing
Photos Barbaroux
Visages of mollusc aquaculture
Mollusc in the different environments
Finfish 97.7% Crustaceans 1.7% Others 0.6%
FRESHWATER PRODUCTION
BRACKISHWATER PRODUCTION
MARICULTURE PRODUCTION
Finfish 8.7% Crustaceans 1.0% Molluscs 46.1% Plants 44.0% Others 0.2%
Finfish 42.7% Crustaceans 50.5% Molluscs 6.1% Plants 0.7%
Prince Edward IslandMain 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 communitiesIn 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 developedPEI 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
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.
Native C. gigasIntroduced C. gigas (Data FAO DIAS)
Importance of transfers:recorded transfers of C. gigas in the world
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
genetic evidence of P. margaritifera transfers between atolls in French Polynesia
Tuamotu archipelago
Tuamotu, Gambier & SociétéArchipelagos
0.01
Takaroa
HivaOa
Mangareva
Manuae
Maupihaa Société Archipelago I
Sociétéarchipelago II
Gambier Islands
Marquises Archipelago
Mangareva
HivaOa
Takaroa
ManuaeMaupihaa
1981/1985 2001
Marquises Archipelago
Figure Courtesy Dr P. Boudry
Impact of transfers: introduction of Bonamia ostreae to Europe
The introduction is believed to have occurred with transfers of flat oysters, Ostrea edulisstocks were moved from California to France and Spain; the French outbreak revealed the parasite in Europe
The origin of the disease remains unclear
California
Europe
Risk associated to transfers
020000400006000080000
100000120000140000160000
1900 1910 1920 1930 1940 1950 1960 1970 1980 1990
YearProduction (mt)
C. angulataC. gigas
O. edulis
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
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…)
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 Marteiliamaurini from mussels to oysters
• speciation refringens - maurini
Other sources of hazard:culture and farming
18S ITS1
Management of diseasesNo vaccines, and treatments are difficult to apply
molluscs do not produce antibodiestreatments would impact the environment
Photo courtesy of Dr DL Choi, NFRDI Pusan
Management of diseases
No vaccines, and treatments difficult to applyHealth management in impacted zones
stock densitiesculture practicestriploids, genetically selected stocks, resistant species
Management of diseases
No vaccines, and treatments difficult to applyHealth management in impacted zonesIn 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 levelsefforts have been made to improve diagnostic methods for diseases of molluscshowever, transfers are not the unique route of disease introduction or emergence
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 limitationsneed for highly qualified personneltime consuming techniquesspecificity / sensitivity
Diagnostic methods
Overcoming limitations of histology & TEM in diagnosisrapid, specific and reliable methods are needed genes of phylogenetic interest are targeted in DNA based assays
• because of the current need to clarify taxonomynew 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 applicationscreening, presumptive and confirmatory methodsmethods corresponding to different levels of technological skills and equipmentsentinel methods
Diagnostic methods
SummaryMollusc production, world-wide
5 main species of economic interesthighly dynamic sector of productionAsia is the main region although important producing countries exist outside the regionvariety of culture systems
Current problemsmost of current problems are shared with other sectorstransfers and introductions as underlying cause of disease outbreakshealth management for invertebrates is a challenge in open watersystemszoning, monitoring and surveillance of important diseases is thecorner stone of health managementother control option may exist depending on the culture system