A number of species of algae live in marine waters, and under the right conditions they can multiply and form blooms. Algal blooms have different impacts - most are harmless, but a few species of algae cause Harmful Algal Blooms (HABs), which can have negative impacts on fish, marine animals, birds, and humans. Species of Alexandrium cause HABs in New England that are commonly referred to as “red tides.” Alexandrium toxin becomes concentrated in shellfish such as quahogs. The shellfish themselves are not affected by the toxin, but eating shellfish tainted with this toxin can lead to paralytic shellfish poisoning (PSP), a potentially fatal human illness. Large-scale monitoring programs operate all along the coast to assess toxin levels in shellfish; if toxins are detected, these areas are immediately closed to harvesting. Contamination from PSP has had a huge impact on fisheries for ocean quahogs. Georges Bank, where ocean quahogs are abundant, has been closed to fishing since 1990 due to the presence of PSP toxins in quahog tissue. In January 2013, a portion of Georges Bank was reopened to the harvest of ocean quahogs and surf clams by vessels using a new PSP testing protocol that was developed through the collaborative efforts of industry, scientists, and managers. This will allow safe harvest of these abundant Georges Bank resources.
- Ocean perch
- Sea Bass
- Turbot (Greenland)
ALSO KNOWN AS:
Clam, Quahog, Black Clam, Hard Clam, Mahogany Quahog
U.S. wild-caught from Maine to Virginia
- FISHING RATE
- HABITAT IMPACTS
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Ocean quahogs.LAUNCH GALLERY
Among the longest-lived marine species in the world, ocean quahogs grow slowly and have low reproduction rates, making them relatively unproductive and unable to support high levels of fishing. Knowing this, managers set harvest limits for the fishery at low levels to try to conserve the ocean quahog resource and keep it at target population levels.
There are two separate fisheries for ocean quahog—one in federal waters (3 to 200 miles offshore) and a smaller one off the coast of Maine in both federal and state waters. The federal ocean quahog fishery was one of the first to be managed under a fishery management plan as directed by the Magnuson-Stevens Act in 1976. It’s also the first U.S. fishery to be managed under an Individual Transferable Quota system, an innovative “catch share” program that allocates shares of the annual harvest to individual fishermen or vessels. The owner of the individual quota can sell his quota to another person permanently or lease it temporarily. When fishermen have a fixed share of the annual harvest, they are able to fish when it is best for them, taking into consideration the market, weather conditions, and other factors. This slows the pace of the fishery, making harvesting quahogs safer, more efficient, profitable, and environmentally friendly—a win-win for the fishermen and the ocean quahog resource. The Maine fishery is managed under a separate quota system.
The large ocean quahogs targeted by the fishery in U.S. federal waters have relatively small, dark, and tough meats and are used in processed clam products such as soups, chowders, and sauces. Smaller ocean quahogs from Maine waters are marketed as “mahogany clams” and are sold on the half-shell market or for steaming.
LOCATION & HABITAT
Ocean quahogs are common around Iceland, in the eastern Atlantic as far south as Spain, and in the western Atlantic as far south as Cape Hatteras, North Carolina. Ocean quahogs live in water between 25 and 1,300 feet deep. In the northern part of their range, they’re found in shallower water closer to shore. The U.S. stock is almost entirely within federal waters (3 to 200 miles from shore), except for a modest amount off the coast of Maine and in waters between 65 and 260 feet deep. Ocean quahogs are rarely found where bottom water temperatures exceed 60 degrees Fahrenheit. Ocean quahog eggs and larvae are found in the water column and drift with the currents until they develop into juveniles and settle to the bottom. They burrow in a variety of sediments, especially fine sand. Their inshore cousins, Mercenaria mercenaria (known as cherrystones or littlenecks), prefer warmer temperatures in shallow bays and estuaries.
Ocean quahogs spawn as separate sexes, releasing eggs and sperm into the water column where the eggs are fertilized. The larvae drift with the currents for at least 30 days until they develop into juveniles and settle to the bottom. Most ocean quahogs spawn once a year, either in the summer or fall. The spawning season is sometimes extended over a number of months as quahogs release eggs and sperm a little at a time.
Ocean quahogs are among the longest-lived marine organisms in the world. Off the U.S. East Coast, where the fishery takes place, ocean quahogs can live for at least 200 years. They grow very slowly and do not start to reproduce until around age 6, and do not reach a commercially harvestable size until about age 20.
Ocean quahogs are filter feeders. They bury themselves in the substrate and pump oxygen-filled water and food particles in through their siphons, which extend above the surface of the substrate. They mostly feed on microscopic algae. Many animals prey on juvenile ocean quahogs, including invertebrates such as rock crabs, sea stars, and other crustaceans, and fish such as longhorn sculpin, ocean pout, haddock, and cod. Once ocean quahogs have reached a certain size, they have a very low predation rate. They burrow in the sandy ocean floor and their thick shells close completely, providing substantial protection from potential predators.
The ocean quahog is a bivalve mollusk—it has two hinged shells that enclose its body. Its shells are thick and oval-shaped. The outside is a dull gray with growth rings that can be used to tell its age. The interior is white with a purple border. Most quahogs in U.S. waters are 2.8 to 4.3 inches in shell length.
Scientists from NOAA’s Northeast Fisheries Science Center, along with industry and academic partners, survey clam populations every 3 years and usually follow these surveys with a full stock assessment.
Ocean quahog population levels are declining despite relatively low fishing rates. Scientists estimate the abundance of the fishable stock (the amount of quahogs large enough to be taken in the commercial fishery) is currently 71 percent above the target level (2013). However, around half of the fishable stock is found on Georges Bank, where fishing for clams has been prohibited for years due to the risk of paralytic shellfish poisoning.
Ocean quahogs grow slowly and have infrequent “recruitment” events, often limited to a small area. (Recruitment refers to young quahogs surviving to adulthood, “recruiting” into the adult population.) As a result, ocean quahogs are relatively unproductive and can only support low levels of fishing.
Harvesting ocean quahogs
Commercial fishermen harvest ocean quahogs with hydraulic clam dredges, which use jets of water to dislodge ocean quahogs from the sandy ocean floor. A smaller “dry” dredge (without hydraulic jets) is used in Maine waters.
Who’s in charge? NOAA Fisheries, the Mid-Atlantic Fisheries Management Council, and state resource management agencies.
Federal waters: Surfclam and Ocean Quahog Fishery Management Plan
- Fishermen must have a permit to harvest ocean quahogs.
- Individual transferable quota system – managers set an annual harvest quota for federal waters and allocate it among individual fishermen or vessel owners. These quotas can be sold or leased.
- Mandatory vessel monitoring systems to monitor closed areas and borders between state and federal jurisdiction.
- Fishermen must maintain and submit logbooks of each fishing trip to document catch.
- Fishermen harvesting ocean quahogs from Georges Bank have additional requirements under the PSP testing protocol.
Maine: The ocean quahog fishery off Maine is managed separately because of differences in biological, fishery, and market characteristics. The portion of this fishery in federal waters off the Maine coast is managed under a relatively small quota that is separate from the quota used to manage the rest of the quahog fishery (described above). To participate in this fishery, vessels must have a separate limited access federal permit, use a mandatory vessel monitoring system, and maintain and submit logbooks of each fishing trip. State authorities manage the portion of this fishery in Maine state waters.
The quota for ocean quahogs has remained constant since 2005, while the annual harvest has ranged from 55 percent to 64 percent of the quota over the same period. The harvest from year to year may vary because of many factors, but is primarily a result of changes in market demand for clam products. In 2012, the ocean quahog fishery produced over 35 million pounds of meats—an increase of 3.3 million pounds compared with 2011. New Jersey had the highest landings with 18.4 million pounds, which was followed by Massachusetts with 14.9 million pounds and Maryland with 1.0 million pounds. Together, Massachusetts and New Jersey accounted for more than 95 percent of total ocean quahog production in 2012.
The 2012 ocean quahog harvest was valued at approximately $25.8 million—an increase of almost $3.8 million from 2011. The average ex-vessel price (price fishermen receive) per pound of meats increased from $0.70 in 2011 to $0.74 in 2012.
Ocean quahog meat is pinkish in color and firmer in texture than other clams, with a somewhat stronger taste. Most ocean quahogs are sold processed (minced, chopped, or cut into strips) or in value-added products such as chowders, bisques, and sauces. Smaller ocean quahogs from Maine waters are marketed as “mahogany clams” and are sold on the half-shell market or for steaming.
Quahogs provide a low-fat, high-quality protein and are an excellent source of selenium iron, and vitamin B12.
|Serving Weight||100 g|
|Fat, total||0.97 g|
|Saturated fatty acids, total||0.094 g|
|Sugars, total||0 g|
|Fiber, total dietary||0 g|
Ocean Quahog Table of Nutrition