Atlantic Surfclam
Atlantic Surfclam
Spisula solidissima
Quick Facts
About the Species
Atlantic surfclams are distributed from the Gulf of St. Lawrence to Cape Hatteras, NC. The U.S. fishery generally concentrates on the populations off the coasts of New Jersey and the Delmarva Peninsula. Dredge and hand harvest are authorized in the commercial fishery, with hydraulic clam dredges being the primary gear type used. The recreational fishery is limited to hand harvest. Surfclams are generally processed for human consumption in soups, chowders, and stews; while a small portion of landings are also sold in the bait market. U.S. wild-caught Atlantic surfclam is a smart seafood choice because it is sustainably managed and responsibly harvested under U.S. regulations. Implementing regulations are found at 50 CFR part 648 subpart E.
Population
Above target population level.
Fishing Rate
At recommended level.
Habitat Impacts
Fishing gear used to harvest surfclams has negative impacts to habitat, but the fishery is managed to minimize these impacts, particularly to sensitive habitat.
Bycatch
Fishing gear used to harvest surfclams is designed to minimize bycatch.
Population Status
- According to the 2020 stock assessment the surfclam stock is not overfished and is not subject to overfishing. Summary stock assessment information can be found on Stock SMART.
Appearance
- Surfclams are the largest bivalves found in the western North Atlantic.
- They grow up to 8.9 inches, although clams larger than 7.9 inches are rare.
- Their shells are thick, triangular, and yellowish-white with rounded edges and concentric ridges.
- Shells do not close fully and gape slightly.
Biology
- Surflclams can live up to 35 years.
- On average, surfclams living in open water live longer than those living inshore.
- Surfclams grow fast, reaching a harvestable size of about 5 inches in 5 to 7 years.
- Growth rates depend on water temperature—southern surfclam populations in warmer water grow more slowly than the more northern populations.
- Some are able to reproduce by age 1, but most spawn by the end of their second year.
- Surfclams spawn from late spring through early fall.
- They shed their eggs and sperm directly into the water column.
- Larvae spend about 3 weeks in the water column as plankton before settling to the bottom to live.
- Surfclams are planktivorous filter feeders, straining tiny plants out of the water to eat.
- Larval surfclams eat algal cells.
- Adults primarily feed on diatoms, green algae, and naked flagellates.
- Snails, crabs, shrimp, and fish, including haddock and cod, feed on surfclams.
Where They Live
- Atlantic surfclams are found in the western North Atlantic from the southern Gulf of St. Lawrence to Cape Hatteras, North Carolina.
- They’re most abundant on Georges Bank, the south shore of Long Island, New Jersey, and the Delmarva Peninsula.
Fishery Management
- NOAA Fisheries, the Mid-Atlantic Fishery Management Council, and state resource management agencies manage the surfclam fishery.
- Managed under the Surfclam-Ocean Quahog Fishery Management Plan:
- Fishermen must have a permit to harvest surfclams.
- Individual transferable quota (catch shares) program – managers set an annual catch limit for federal waters and allocate it among individual fishermen or vessel owners. These quotas can be sold or leased.
- Minimum size, which can be suspended by managers if they can demonstrate the harvest of small surfclams is below a certain threshold.
- Closed areas due to environmental degradation or to toxins that cause paralytic shellfish poisoning (PSP).
- Fishermen harvesting surfclams from Georges Bank have additional requirements under the PSP testing protocol.
- Mandatory vessel monitoring systems.
- Fishermen must maintain and submit logbooks of each fishing trip to document catch.
- Surfclams support valuable fisheries in New Jersey and New York state waters (within 3 miles of shore); state authorities are responsible for managing these fisheries.
Harvest
- In 2019, commercial landings of surfclam totaled more than 34.3 million pounds and were valued at $29.3 million, according to the NOAA Fisheries commercial fishing landings database.
- Surfclams are the most important commercial clam species harvested in the United States.
- Commercial fishermen harvest surfclams with hydraulic clam dredges—essentially large, heavy sleds pulled along the sea floor. High-pressure jets blast water into the sediment, which temporarily liquefies it and allows a steel blade to pass through the first few inches of substrate and scoop the clams onto the dredge, where they are captured in a cage made of steel bars.
- Atlantic surfclams burrow into sandy bottoms on the continental shelf, an environment that is thought to recover quickly after a hydraulic clam dredge passes over it.
- The bars on commercial clam dredges are spaced several inches apart so they do not collect anything but the targeted surfclams.
- The surfclam fishery is managed under an individual transferable quota program that provides fishermen with more flexibility on when to fish, slows the pace of the fishery, and increases its efficiency, significantly reducing bycatch.
Featured News
Grilled tuna lemon with mayo. Credit: North Carolina Sea Grant/Vanda Lewis.
Science Overview
The most recent stock assessment update for Atlantic surfclam was in 2016, where the stock was declared not overfished and overfishing was not occurring. The next assessment for surfclam is scheduled for 2020.
Research, Surveys, & Data
Atlantic Surfclam Stock Statuses Based on Most Recent (2016) Stock Assessment
| Spawning Stock Biomass (SSB) | 46.355 million mt (2015) |
|---|---|
| SSBThreshold | 18.25 million mt |
| SSB/SSBThreshold | 2.54 |
| Overfished Definition | The stock is overfished when SSB < ½ SSBMSY |
| Overfished? | No |
| Fishing Mortality Rate (F) | 0.009 (2015) |
| FThreshold | 0.03 |
| F/FThreshold | 0.295 |
| Overfishing Definition | Overfishing occurs when F > FMSY; where FMSY = M (natural mortality rate) |
| Overfishing? | No |
| Current Rebuilding Program? | No. Declared rebuilt. |
| Next Stock Assessment | Assessment scheduled for 2020 |
