Hard Clam Aquaculture By Carly Cappelluzzo

Hard 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 Feeder  Benthic  Mobile to an extent  “Broadcast spawners”

Ecology 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 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 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 The houseboat “ Cynthia ” on Barnegat Bay, NJ, circa 1915.

The 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 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.)

Spawn  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 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 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 days.

Larval Development g. Early trochophore larva (post-gastrulation) h. Fully developed trochophore larva i. D-hinge veliger larva j. Unbonate veliger larva k. Pediveliger larva l. Developed post-set juvenile a. Unfertilized egg and sperm b. Fertilized egg and polar body formation c. First cell division d. Four-cell embryo e. Eight-cell embryo showing spiral cleavage f. Morula hellfishing/quahog_dev.html

Post 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

Upwellers  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 ) 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 ) 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.

Raceways  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-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.

Harvest  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 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.

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