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Hard Clam AquacultureHard Clam Aquaculture
By Carly CappelluzzoBy Carly Cappelluzzo
Hard Clam BiologyHard Clam Biology
Taxonomy: K: Animalia P: Mollusca C: Bivalvia O: Veneroida F: Veneridae G: Mercenaria S: M. mercenaria
Taxonomy: K: Animalia P: Mollusca C: Bivalvia O: Veneroida F: Veneridae G: Mercenaria S: M. mercenaria
Filter FeederBenthicMobile to an extent“Broadcast spawners”
Ecology and DistributionEcology and Distribution Live in shallow bays and intercoastal waters. Prefer good water flow with abundant photoplankton. Predators include crabs, some fish species, rays, gulls
and migratory shorebirds and waterfowl. Distributed along the entire atlantic coast of North
America. (most abundant from Cape Cod to New Jersey) Can tolerate a wide range of temperatures and salinities. Has been introduced to the pacific coast via aquaculture.
Live in shallow bays and intercoastal waters. Prefer good water flow with abundant photoplankton. Predators include crabs, some fish species, rays, gulls
and migratory shorebirds and waterfowl. Distributed along the entire atlantic coast of North
America. (most abundant from Cape Cod to New Jersey) Can tolerate a wide range of temperatures and salinities. Has been introduced to the pacific coast via aquaculture.
History as a ResourceHistory as a Resource Native Americans first harvested “quahogs” for food and wampum. Tuckerton first named Clamtown and was a major port for shellfish. By the mid 20th century clams and oysters were over-fished in NJ and
the industry suffered.
Native Americans first harvested “quahogs” for food and wampum. Tuckerton first named Clamtown and was a major port for shellfish. By the mid 20th century clams and oysters were over-fished in NJ and
the industry suffered.
The "Jesse G" taking on clams off Atlantic City. 1- Arnold Pratt Cramer; 2- Daniel Arnold Cramer; 3- Harold Cramer; and 4- the Claridge Hotel. (Photo courtesy of Arnold Nathan Cramer.)
Aquaculture HistoryAquaculture History Hard Clam aquaculture was first attempted by wild clammers who
found “seed” and planted it on leased land or “hid” it. Oyster culture had been done since early 19th century. First hatchery rearing work done by Harold Haskin funded by
Campbell’s in 1950’s. Huge set of clams in late 60’s and 70’s at Goose Bar inspired local
clammers to take classes at VIMS to learn to spawn and rear clams. First attempts back in NJ were failures and changes in location,
salinity, and grow-out methods occurred and helped. Namely the use of plastic mesh screen.
Hard Clam aquaculture was first attempted by wild clammers who found “seed” and planted it on leased land or “hid” it.
Oyster culture had been done since early 19th century. First hatchery rearing work done by Harold Haskin funded by
Campbell’s in 1950’s. Huge set of clams in late 60’s and 70’s at Goose Bar inspired local
clammers to take classes at VIMS to learn to spawn and rear clams. First attempts back in NJ were failures and changes in location,
salinity, and grow-out methods occurred and helped. Namely the use of plastic mesh screen.
Second Cape Shore Laboratory, built by Harold Haskin in 1955.The houseboat “Cynthia” on Barnegat Bay, NJ, circa 1915.
The BasicsThe Basics
Step 1: Select Brood Stock Step 2: Spawn Step 3: Planktonic Larval Stage Step 4: Post Set (Downwellers) Step 5: Upwellers (nursery grow
out) Step 6: Raceways (nursery) Step 7: Planted in the bay under
screens Step 8: Harvest for seafood market
Step 1: Select Brood Stock Step 2: Spawn Step 3: Planktonic Larval Stage Step 4: Post Set (Downwellers) Step 5: Upwellers (nursery grow
out) Step 6: Raceways (nursery) Step 7: Planted in the bay under
screens Step 8: Harvest for seafood market
Selecting BroodstockSelecting Broodstock
Broodstock are selected based on the following: Notata Proven spawners Fast growing Region from
Broodstock are selected based on the following: Notata Proven spawners Fast growing Region from
wild color phenotype on the left, and clams that are homozygous (top, middle) and heterozygous for the notata shell color phenotypes (Photo by P. Baker.)
SpawnSpawn In wild, clams are triggered to spawn by the spring tide. In hatchery, we simulate this with thermal shocking in a
shallow trough. Male clams release sperm, which triggers other males to
do the same, females then follow A clam will release its gametes for a couple of minutes at
a time. We place the releasing clams in separate containers so
that a few males and one female are in seclusion. Eggs are fertilized in minutes. Too much sperm may injure or kill an egg.
In wild, clams are triggered to spawn by the spring tide. In hatchery, we simulate this with thermal shocking in a
shallow trough. Male clams release sperm, which triggers other males to
do the same, females then follow A clam will release its gametes for a couple of minutes at
a time. We place the releasing clams in separate containers so
that a few males and one female are in seclusion. Eggs are fertilized in minutes. Too much sperm may injure or kill an egg.
Planktonic Larval StagePlanktonic Larval Stage We pour the seawater with freshly
fertilized eggs over a fine mesh sieve (35 microns).
Fertilized eggs are then released into large larval tanks with highly filtered seawater around 25 degrees celsius.
They are fed unicellular planktonic algae that we grow in the lab.
These tanks are “drained down” every other day until clams “set”.
Clams set after 8 - 10 days.
We pour the seawater with freshly fertilized eggs over a fine mesh sieve (35 microns).
Fertilized eggs are then released into large larval tanks with highly filtered seawater around 25 degrees celsius.
They are fed unicellular planktonic algae that we grow in the lab.
These tanks are “drained down” every other day until clams “set”.
Clams set after 8 - 10 days.
Larval DevelopmentLarval Development
g. Early trochophore larva (post-gastrulation)h. Fully developed trochophore larvai. D-hinge veliger larvaj. Unbonate veliger larvak. Pediveliger larva
l. Developed post-set juvenile
a. Unfertilized egg and spermb. Fertilized egg and polar body formationc. First cell divisiond. Four-cell embryoe. Eight-cell embryo showing spiral cleavagef. Morula
http://seagrant.gso.uri.edu/G_Bay/HabitatEco/Shellfishing/quahog_dev.html
Post Set - DownwellersPost Set - Downwellers
Post set clams are drained onto sieves and placed into downwellers.
Look like apple-butter Downwellers are 18 in PVC with a mesh bottom
(starting at 130 microns). They sit in a trough and water is downwelled through them using an air system which directs flow.
Unicellular algae is pumped into trough to feed in morning and night.
Water is replaced and post set is washed with seawater every day for first couple days then every other day.
Clams develop byssal threads. Post set clams go onto larger mesh sizes as they
grow until they reach 220 microns or so
Post set clams are drained onto sieves and placed into downwellers.
Look like apple-butter Downwellers are 18 in PVC with a mesh bottom
(starting at 130 microns). They sit in a trough and water is downwelled through them using an air system which directs flow.
Unicellular algae is pumped into trough to feed in morning and night.
Water is replaced and post set is washed with seawater every day for first couple days then every other day.
Clams develop byssal threads. Post set clams go onto larger mesh sizes as they
grow until they reach 220 microns or so
UpwellersUpwellers
When clams are large enough they can go into upwellers and be fed raw seawater. (outside at nursery)
Upwellers use the same PVC and mesh (larger 250 - 1400) as downwellers but water flows through bottom of mesh and up and out of pvc.
Creates puff of clam seed on mesh held together by byssal threads.
Clams that are caught on a 1460 micron sieve are ready for raceways.
When clams are large enough they can go into upwellers and be fed raw seawater. (outside at nursery)
Upwellers use the same PVC and mesh (larger 250 - 1400) as downwellers but water flows through bottom of mesh and up and out of pvc.
Creates puff of clam seed on mesh held together by byssal threads.
Clams that are caught on a 1460 micron sieve are ready for raceways.
RacewaysRaceways
Raceways are seeded with 1460 micron or larger seed from upwellers.
In one month they will grow enough (conditions permitting) to be sorted out, possible 1/4inch seed.
Raceways are re-seeded with sorted seed. Volumes:
15 liters - up to 1800 micron 20 liters - what falls through a 1/4 inch sieve 40 liters - 1/4 inch Up to 100 liters - 3/8 inch (plantable)
Raceways are seeded with 1460 micron or larger seed from upwellers.
In one month they will grow enough (conditions permitting) to be sorted out, possible 1/4inch seed.
Raceways are re-seeded with sorted seed. Volumes:
15 liters - up to 1800 micron 20 liters - what falls through a 1/4 inch sieve 40 liters - 1/4 inch Up to 100 liters - 3/8 inch (plantable)
Bay Grow-outBay Grow-out
A clam lease is 2 acres and is leased from the state. Plantable seed is planted under 1/4 inch screen in August - October. PVC markers let us know the boundaries of our lease and the
location of screens. Screen protects from predators (namely the blue crab and cow-nose
rays. Clams burrow into the sediment and filter feed from the productive
late-summer water.
A clam lease is 2 acres and is leased from the state. Plantable seed is planted under 1/4 inch screen in August - October. PVC markers let us know the boundaries of our lease and the
location of screens. Screen protects from predators (namely the blue crab and cow-nose
rays. Clams burrow into the sediment and filter feed from the productive
late-summer water.
HarvestHarvest When clams reach legal size
(1.5 inches long) they are harvested by hand with a rake.
Farmed clams make up most of the shellfish sold in markets.
Their taste is equal to wild clams, but their harvest impact is much less.
When clams reach legal size (1.5 inches long) they are harvested by hand with a rake.
Farmed clams make up most of the shellfish sold in markets.
Their taste is equal to wild clams, but their harvest impact is much less.
Environmental BenefitsEnvironmental Benefits
Clams filter the water improving water clarity. Improved water clarity can allow SAV to grow in
the bay. Remove and absorb nitrogen from the system. (1
oyster when harvested has trapped 1 gram of nitrogen).
Clam Farming relieves stress on wild population. Nets which cover clams in bay provide substrate
for algae and habitat for epifauna such as crabs, shrimp, and fish species.
Clams filter the water improving water clarity. Improved water clarity can allow SAV to grow in
the bay. Remove and absorb nitrogen from the system. (1
oyster when harvested has trapped 1 gram of nitrogen).
Clam Farming relieves stress on wild population. Nets which cover clams in bay provide substrate
for algae and habitat for epifauna such as crabs, shrimp, and fish species.
SourcesSources http://bassriverhistory.blogspot.com/2009_07_01_archive.
html http://www.state.nj.us/seafood/Aquaculturereport.pdf http://en.wikipedia.org/wiki/Hard_clam http://www.thefreelibrary.com/Northern+quahog+
(hard+clam)+Mercenaria+mercenaria+abundance+and...-a0135967953
http://www.hsrl.rutgers.edu/about/history.htm http://www.fao.org/fishery/culturedspecies/
Mercenaria_mercenaria/en http://fishweb.ifas.ufl.edu/Pbaker/PBaker.htm
http://bassriverhistory.blogspot.com/2009_07_01_archive.html
http://www.state.nj.us/seafood/Aquaculturereport.pdf http://en.wikipedia.org/wiki/Hard_clam http://www.thefreelibrary.com/Northern+quahog+
(hard+clam)+Mercenaria+mercenaria+abundance+and...-a0135967953
http://www.hsrl.rutgers.edu/about/history.htm http://www.fao.org/fishery/culturedspecies/
Mercenaria_mercenaria/en http://fishweb.ifas.ufl.edu/Pbaker/PBaker.htm