Transcript GENIMPACT Genetic impact of the aquaculture of shellfish

GENIMPACT
Genetic impact of the aquaculture of shellfish in Europe
• Species considered
• Mussel
o Blue mussel, Mytilus edulis
o Mediterranean mussel, M. galloprovincialis
• Oyster
o Flat oyster, Ostrea edulis
o Pacific oyster, Crassostrea gigas
o Portuguese oyster, Crassostrea angulata
• Scallop
o Coquille St Jacques, King scallop, Pecten maximus
o Mediterranean scallop, Pecten jacobaeus
• Lobster
o European lobster, Homarus gammarus
• Others not considered
o Clams
 Manila clam, Ruditapes philippinarum
 Carpet clam, Ruditapes decussata
o Cockles, Cerastoderma edule
o Razor shells, Ensis spp.
GENIMPACT
Genetic impact of the aquaculture of shellfish in Europe
• Mussels
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Three species of mussel distributed
around Europe
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Blue mussel, Mytilus edulis
Mediterranean mussel, M. galloprovincialis
Baltic mussel, M. trossulus
Baltic mussel has no significant
commercial value
Mediterranean mussel has expanded its
range out of Mediterranean and
hybridises with blue mussel
Hybrid zone extends from Atlantic France
to northern Scotland
Mosaic of pure species, and hybrids
Needs identifying, mapping and
monitoring to identify species (or hybrids)
being cultivated
Ground laying aquaculture of mussels
involves movement of seed between
areas and this can be having a genetic
impact
No significant hatchery culture at present
although R&D is being carried out
Distribution of three mussel species in Europe
GENIMPACT
Genetic impact of the aquaculture of shellfish in Europe
• Oysters
• Flat or native oyster, Ostrea
edulis
• Traditional oyster cultured from
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Roman times
Massive decline in production
since its heyday in the 1800s
Overfishing, pollution and
diseases (Bonamiosis)
Selective breeding for disease
resistance carried out at
IFREMER
New genetic map has allowed
the search for Quantitative Trait
Loci (QTLs) to begin
GENIMPACT
Genetic impact of the aquaculture of shellfish in Europe
• O. edulis is widespread
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across Europe
Patchy distribution
Main genetic impact is
reduction in genetic
variability from hatchery
activities
One microsatellite study
showed significant loss of
alleles from hatchery
operations
No loss of heterozygosity
populations
No. of alleles
locus -1
Heterozygosity
wild
17.6
0.829
hatchery
9.2
0.839
GENIMPACT
Genetic impact of the aquaculture of shellfish in Europe
• Oysters
• Pacific cupped oyster Crassostrea
gigas
• Non-native
• Highly productive and the most
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important oyster species world-wide
Has naturalised in many regions, for
example the Atlantic coast of France
In some areas it is a pest species, for
example in The Netherlands where it
has recently invaded.
It is now invading southern Britain
It competes for settlement space with
native species such as mussels,
barnacles and flat oysters creating a
significant ecological impact on
sheltered rocky shores
Aquaculture vs the environment
The classic way to eat oysters:
half a dozen with a nice white wine!
GENIMPACT
Genetic impact of the aquaculture of shellfish in Europe
• Seed for the industry is either produced
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in hatcheries
Or farmers collect natural spatfall
Seed oysters are deployed in bags on
trestles at low water
Most extensive areas of culture are in
the Marrennes-Oleron region of France
Hybridises with the Portuguese oyster
(Crassostrea angulata) where the two
species overlap between France and
Portugal
Significant genetic impact if hybridisation
is extensive
Risk of loss of genetic resource
represented by Portuguese oyster
However, Portuguese oyster is nonnative
Was introduced hundreds of years ago.
GENIMPACT
Genetic impact of the aquaculture of shellfish in Europe
• Oysters: genetic impact of
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the use of triploids
An increasing proportion of
the oysters on the European
market are triploids
They are mainly sterile
Insignificant quantity of
reproduction
Any eggs, sperm or embryos
are mostly non-viable
No genetic impact on
naturalised populations
Valuable method to
ameliorate invasion due to
aquaculture
Tetraploid male
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Diploid female
Triploid oysters
Tetraploid broodstock are
difficult to produce and must
be prevented from escape
Requires the active involvement
of Government Agencies
GENIMPACT
Genetic impact of the aquaculture of shellfish in Europe
• Scallops
• Cocquille St Jacques, King scallop, Pecten
maximus
• Mediterranean scallop, P. jacobaeus
• Both species are cultured – usually on
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longline systems
Natural spat collected – very little
hatchery produced seed
There has been extensive re-stocking
from hatchery seed in the Rade de Brest,
France, over many years
Local stock used as broodstock – good
management strategy
However, risk of genetic impact through
reduced genetic variation in hatchery
product
More information needed on the
population substructure of P. maximus and
P. jacobaeus
GENIMPACT
Genetic impact of the aquaculture of shellfish in Europe
• Lobster (Homarus gammarus)
• One of most valuable shellfish by weight in
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Solitary, highly active, primarily nocturnal
predators – unlike bivalves
Distributed throughout Europe
Four main genetically identifiable groups:
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northern Norway,
the Netherlands,
the Aegean
Atlantic and outer Mediterranean coasts.
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commercial movements of lobsters between
these areas
Aquaculture production, although limited, is
growing
GENIMPACT
Genetic impact of the aquaculture of shellfish in Europe
• Lobster aquaculture
• Very difficult because of cannibalism of
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juveniles
Has been used extensively for re-stocking
trials
Source of the berried females not considered
Only a few females used leading to loss of
genetic variability in re-stocked juveniles
One Norwegian hatchery producing market
size lobsters in captivity
Larvae from cultured lobsters are less fit that
those from wild-caught lobsters
This is an important potential genetic impact
on wild populations if cultured lobsters are
released
GENIMPACT
Genetic impact of the aquaculture of shellfish in Europe
• Key considerations
• We need to understand more about the complex pattern of hybrids
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and pure species of mussels in order to reduce potential genetic
impact
Hatchery culture of flat oysters significantly reduces genetic
variation
Useful selective breeding for disease resistance
Pacific oyster is invasive so has ecological impact
Also has genetic impact by hybridizing with the Portuguese oyster
Triploids could help to ameliorate effect of aquaculture on the
spread of the species
Little genetic impact in scallops except possibly through re-stocking
in Rade de Brest
Genetic impact on lobsters via movements of adults and through
restocking efforts
• Different species create different problems and require different
solutions