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Clam, Quahog (Mercenaria mercenaria [Northern], M. campechiensis [Southern])
Also known as: Hard shell clam
Source: Wild-caught and farm-raised mostly in West Florida

Southern quahogs range from New Jersey to the Gulf of Mexico and are especially abundant on Florida’s Gulf coast, particularly in bays and estuaries. Northern quahogs are found from the Gulf of St. Lawrence, along the East Coast, around the Florida peninsula, and into the Gulf coast of Texas; however, they are rare on the Gulf coast of Florida.

Quahogs spend most their life buried in sand or sandy mud bottoms from the mean high tide line to under 50 feet of water. They prefer moderately salty water but will tolerate a variety of salinities. In bays and estuaries, clams live near seagrass beds and algal mats, but in the Gulf, they’re also found on bare sand flats. They generally live near the mouths of bays and estuaries, where tides and currents deliver food and oxygen-rich water to them.


Quahogs grow quickly in Florida waters—up to nearly three inches in diameter in two years. As they grow, they form ridges on their shell, roughly one a year. Scientists examine a cross section of the shell to determine a clam’s age like growth rings on a tree. Southern quahogs grow up to seven inches in diameter and live at least 22 years in Florida waters; northern quahogs grow to more than four inches and live up to 30 or so years.

Quahogs can reproduce when they’re about one year old. They begin life as males, but about half change to females usually by the end of their first year. They spawn in the spring and fall. Males release sperm into the water, stimulating females to release their eggs. Females can spawn several times a year, producing millions of eggs. Sperm and eggs unite by chance. Fertilized eggs hatch and turn into free-swimming larva within about a day. As the clam begins to develop its shell, organs, and foot, it drops to the seafloor, sending out thin filaments (the developing foot) to hold it in place. As the foot develops, the clam uses it to bury into sand or mud, leaving only its siphons protruding.

Clams use one of their siphons to pump seawater with tiny plants and animals into their shell. They filter these plants and animals over the gills and pass suitable items to their mouth. They expel unwanted items through their other siphon. Predators include whelks, moon snails, and oyster drills—they can easily penetrate the clam’s shell to reach the clam inside. Crabs, pufferfish, drums, sea trout, skates, and rays also eat clams. Clams protect themselves from predators by burrowing deeper; their shell also offers some protection, especially when they’re larger.


Clams are bivalve mollusks—they have two hinged shells connected by a ligament and two adductor muscles that close the shells. The shells encase a soft-bodied clam. Clams have two siphons and a hatchet-shaped foot. Quahog shells are brownish gray to white. Both have symmetrical, oval-shaped shells, but the southern quahog’s shells tend to be thicker. The outside of the shells is ridged, except for smooth area near the hinge on the northern quahog’s shell. The inside is white and smooth with two marks where the adductor muscles attach to the shell. The inside of the northern quahog’s shell is deep purple near the outer edge and hinge.


There are two commercially important varieties of hard clams harvested in Florida, the northern quahog and the southern quahog. Historically, Native Americans harvested hard clams for both food and currency. Commercial fishermen began harvesting hard clams in the 1880s. The clam industry has ebbed and flowed over the years. Landings grew steadily into the early 1900s when southern hard shell clam beds in southwest Florida supported an extensive fishery, at one point considered to be the largest in the world. In 1931, fishermen harvested more than a million hard shell clams. The southwest Florida fishery collapsed in 1947, possibly due to diversion of freshwater flows and a massive red tide, and by 1950, fishermen harvested only 4,000 pounds of clams a year. Fishermen moved on to other clam beds on both coasts, producing an average of 428,000 pounds a year from 1971 to 1988. Harvests increased dramatically in the mid-1980s—fishermen discovered a large concentration of clams in Indian River Lagoon on the central Atlantic coast of Florida. Clammers from as far away as New York and Rhode Island came down to harvest these clams. Harvests in the mid-1990s averaged 1.4 million pounds and $10 million; 90% of the harvest was from the Indian River Lagoon area. Harvests on both coasts have since generally declined as clam populations have declined. Today, fishermen harvest wild clams from Florida’s central and Atlantic coast waters—harvests on the Atlantic coast have averaged about 38,000 pounds in the past decade; harvests on the Gulf coast have averaged 174,000 pounds.

Because of declines in the number of wild clams in Florida waters, hard clam aquaculture supplements a large portion of Florida’s clam production. Clam production is both ecologically and economically important to Florida. Clams feed on algae and nutrients from the water, improving water quality, and clam farming improves habitat for many marine organisms. Florida is one of the top clam producers in the nation—this industry supports hundreds of jobs in coastal communities throughout the state.

The Florida Fish and Wildlife Commission is mainly responsible for regulating the wild clam fishery; the Florida Department of Agriculture and Consumer Services (FDACS) is mainly responsible for regulating clam aquaculture. FDACS is also responsible for ensuring all harvest areas (for both wild and aquaculture production) meet water-quality standards to protect public health.

Methods Seasons Landings
Commercial Recreational

Clam aquaculture has increased rapidly in the past three decades and accounts for the vast majority of Florida’s clam production. In 2012 (the most recent data available), clam farmers (on both coasts) planted nearly 251 million seed clams and harvested and sold more than 130 million clams, with revenues of nearly $11.6 million. Wild harvests have generally declined since the mid-1990s, averaging 174,000 pounds on Florida’s Gulf coast in the past decade, about 79% of the state’s total production. On the Gulf coast, 2013 production totaled 183,240 pounds with revenues of nearly $921,000.

Source: NOAA Fisheries Annual Commercial Landings Statistics, Florida Department of Agriculture and Consumer Services


Landings Summary Data :  
1992
 To 
2016



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1992$9,8012,500
1993$165,30243,263
1994$176,49724,399
1995$360,94435,685
1996$2,260,020205,130
1997$4,337,769396,210
1998$4,989,329540,265
1999$6,815,962755,272
2000$5,225,106548,572
2001$4,739,639508,889


Overview Current Abundance Additional Reasearch
Overview

Florida’s Fish and Wildlife Conservation Commission (FWC) monitors Florida’s commercial wild clam harvests through a trip ticket program which requires dealers to maintain records of the seafood they purchase. Records include information about the harvester, the amount of oysters harvested, where they were harvested, and their value. Reporting of aquacultured clam harvest is voluntary.

The Florida Department of Agriculture and Consumer Services collects data on clam aquaculture, including the number of seed clams planted as well as the number and value of clams harvested and sold through mail, phone, and field surveys.


Current Abundance

There is no current assessment available for wild clam populations in Florida.


Additional Research

FWC’s Fish and Wildlife Research Institute (FWRI) has studied hard clam biology and behavior to better understand Florida’s wild clam populations and determine methods to help populations recover from recent declines. FWRI has also developed GIS-based maps to describe areas suitable for clam aquaculture that will not interfere with wild harvest.

The University of Florida’s Institute of Food and Agricultural Sciences Shellfish Aquaculture Research and Extension Program conducts a variety of research related to clam aquaculture.


Who's Responsible Management Program
Who's Responsible

The Florida Fish and Wildlife Conservation Commission (FWC) and the Florida Department of Agriculture and Consumer Services (FDACS) share in the responsibility for managing the wild clam fishery in Florida’s state waters. FWC handles commercial fishing licenses and establishes minimum size limits and gear and time restrictions. FDACS monitors Florida’s clams for health and human safety. They open and close harvest areas based on rainfall models and sampling.

FDACS is responsible for regulating clam aquaculture and leasing water bottoms for aquaculture purposes.

FDACS also regulates and inspects all shellfish processing plants for compliance with shellfish handling, labeling, and food safety requirements


Management Program

Wild:

Commercial:

  • Fishermen must have the appropriate licenses and permits to harvest and sell clams, including a saltwater products license and a shellfish endorsement. Fishermen must take a course in sanitary shellfish harvesting, handling, and transportation practices.to get this endorsement.
  • Fishermen may only harvest clams from open waters (determined by FDACS).
  • Fishermen may only harvest clams by hand, rake, or tongs. Rakes and tongs must have at least 7/8-inch space between teeth/bars to allow small clams to pass through without being harvested. Unless they have a special license, they may not use any powered mechanical device such as a dredge—these are prohibited to prevent overfishing and potential damage to habitat. Fishermen may not use any equipment to harvest clams in seagrass beds to prevent damage to this sensitive habitat.
  • Fishermen may only harvest clams 1-inch hinge width or larger. They must sort clams immediately and return small clams back to the water from where they came. This minimum size limit allows most clams to mature and spawn before they’re harvested (clams spawn when they’re about ¾-inches hinge width). It also addresses market issues—clams 1-inch or greater hinge width are much more valuable than smaller clams. The minimum size limit was designed to help maintain the resource and increase the economic yield from the fishery.
  • Fishermen may not harvest clams at night for enforcement reasons.
  • Fishermen must be able to shade harvested clams from the sun at all times.
  • Clam harvest is prohibited or restricted in certain areas.

Recreational:

  • Recreational fishermen follow similar regulations to commercial fishermen, except they may harvest no more than five gallons of clams per person or 10 gallons per vessel.

Farmed:

FDACS requires clam farmers to be registered and to follow established best management practices for protecting water quality, habitat, native species, and public health and preventing disease. They must also obtain any required federal and local permits and follow any applicable federal and local regulations. FDACS conducts site inspections to ensure operations are in compliance with required practices.