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SHELLFISH 101 A Primer on Local Shellfish Life History and Care
CHRISTINA LOVELY
MARINE FISHERIES BIOLOGIST Town of Falmouth, MA
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Overview
Introduction to Shellfish
Local Shellfish Species
Falmouth’s Shellfish Propagation
Shellfish Data Collection
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What are “Shellfish”?
Mollusks
Gastropods Chitons Cephalopods Bivalves
(Shellfish)
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What are “Shellfish”?
Shellfish are BIVALVE mollusks
Meaning they have two shells connected by a hinge
Shellfish are filter feeders
Feed on phytoplankton (microscopic plants) in the seawater
Many species are candidates for water quality operations
Shellfish species differ in:
Morphology (shape and size)
Ecology (where and how they live)
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Shellfish Life Cycle
Fertilized egg
Unfertilized egg
Pediveliger
Early spat
Later spat
SETTING
Veliger
Trocophore
SPAWNING
Adults
Sperm
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New England Shellfish Species
Oyster
Quahog
Bay Scallop
Softshell Clam
Sea scallop
Blue mussel
Razor clam
Blue mussel
Ribbed mussel
Blood ark
Surf Clam
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Commonly Harvested Shellfish Species
Oyster
Quahog
Bay Scallop
Softshell Clam
Sea scallop
Blue mussel
Razor clam
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Commonly Harvested Shellfish Species
Oyster
Quahog
Bay Scallop
Softshell Clam
Sea scallop
Blue mussel
Razor clam
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Eastern Oyster Crassostrea virginica
Popular restaurant delicacy
High filtration rate
Fast-growing, sessile species, no foot
Highly tolerant of extreme environmental conditions
Can close their shells completely
Moderately deep, elongated, gray-white to gray-brown, rough, spoon-shaped shell
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Northern Quahog Mercenaria mercenaria
Sold by names reflecting size (1 1/2 to 5 inches), from littlenecks to cherrystones, topnecks and chowders
Slow-growing, infaunal species with a foot for burrowing
Tolerant of varying environmental conditions
Can close their shells completely
Have an off-white, oval, symmetrical shell with a purple or violet border inside
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Bay Scallop Argopecten irradians
Harvested for adductor muscle, not stomach
Highly mobile, swim by jet propulsion
Specialized morphology with irridiophores
Intolerant of varying environmental
conditions
Have an almost perfectly circular
corrugated shell
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Softshell Clam Mya arenaria
“Steamer clam” or common “fried clam” averages 1 1/2 to 3 inches in length
Infaunal species with a foot for burrowing
Cannot close completely because of a protruding siphon
Intolerant of varying environmental conditions
Have an oval-shaped shell that is thin and very brittle
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Shellfish ABC’S
A B C S t
t
a
c
h
u
r
r
o
w
w
i
m
a
n
’
t
c
l
o
s
e
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Shellfish 123’s
1
2
3
1-inch wide legal quahog
2-inch long legal softshell clam
3-inch long legal oyster
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The Life of Falmouth Shellfish
Shellfish seed (baby shellfish) arrives to Falmouth MES from hatcheries in late May
Seed cared for in primary nursery upweller tanks until seed can retain in grow-out gear
Different species have different life histories: so different husbandry strategies, gear, and growing techniques used for each
Gear maintained until late fall, when shellfish are seeded or bottom-planted
Seeded shellfish areas open the following fall for the taking of shellfish (depending on species)
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Species Falmouth Propagates
OYSTERS QUAHOGS BAY SCALLOPS
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Care and Propagation of Shellfish
Traditional upweller
Can clean animals easily with freshwater
Need frequent cleanings
Can be grown in various in grow-out gear
Traditional upweller
Can clean animals easily with freshwater
Need routine cleanings
At a certain size, need grow-out gear with substrate
Modified upweller silos
Cannot be cleaned with freshwater
Need frequent
cleanings
Need ample space in
grow-out gear
OYSTERS QUAHOGS BAY SCALLOPS
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Falmouth Marina Upwellers
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Oyster seed
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Oyster grow-out gear
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Oysters prior to seeding
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Quahog seed
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Quahog grow-out gear
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Quahogs prior to seeding
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Bay scallop seed
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Bay scallop grow-out gear
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Bay scallops prior to seeding (right)
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2018 Little Pond Farm
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OYSTERS
BAY SCALLOPS
QUAHOGS
2018 Little Pond Farm
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Shellfish Data Collection
Helps to assess the health and growth of shellfish
Shell height (umbo to bill) and wet weight are good measurements to take
Doing this routinely helps to catch any disease early
Helps to ensures receipt of a good product from hatcheries
Helps to make informed decisions of where to buy seed from
Combined with water quality data, provides a powerful snapshot of the growing season
Water temperature, dissolved oxygen, and data can be useful
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Shellfish data collection instruments
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Measuring an oyster’s growth
DORSAL SIDE
VENTRAL SIDE
Umbo
Growth lines
Shell height (umbo to bill)
Bill
OYSTER ANATOMY
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Measuring a quahog’s growth
DORSAL SIDE
VENTRAL SIDE
Umbo
Growth lines
Shell height (umbo to bill)
Bill
QUAHOG ANATOMY
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Measuring a bay scallop’s growth
DORSAL SIDE
VENTRAL SIDE
Umbo Growth lines
Shell height (umbo to bill)
Bill
BAY SCALLOP ANATOMY
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Shellfish data sheet
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Shellfish growth chart
0
10
20
30
40
50
60
70
80
AV
ER
AG
E S
HELL
HEIG
HT
(MM
)
2018 FALMOUTH SHELLFISH SEED GROWTH
Oyster Quahog Bay Scallop
Upweller Grow Out Gear
Upweller Grow Out Gear
Upweller Grow Out Gear
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In Summary
Shellfish are BIVALVE mollusks: two shells connected by a hinge
Shellfish are filter feeders, consuming phytoplankton in seawater
There are many shellfish species native to New England, and several
are harvested for consumption
Shellfish species differ in legal harvest sizes
Shellfish species have different care needs and growing methods
Data collection is valuable to assessing shellfish health and growth