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