Distribution, biology and ecology, and historical fisheries

Rangia and marsh clams, Rangia cuneata, R. flexuosa, and Polymesoda caroliniana, in eastern Mexico: distribution, biology and ecology, and historical fisheries

Armando T. Wakida-Kusunoki


People have gathered Rangia and marsh clams along the eastern Mexico coast (Fig. 1) since prehispanic times. The clam species are almeja gallo or rooster clam, Rangia cuneata; almeja casco or helmet clam, R. flexuosa; and almeja negra o prieta or black clam,


Polymesoda caroliniana (Fig. 2). They form the basis for the most important clam fishery on this coast. Next to them in importance is the southern quahog, Mercenaria campechiensis (MacKenzie et al., 2002). Rangia cuneata is the principal species targeted by fishermen and has the highest economic value. Rangia flexuosa and P. caroliniana at times are targeted for harvesting, but many are retained for sale when harvested with R. cuneata (Ruiz, 1975; Baqueiro and Echevarria, 1997).


This paper describes the distribution, biology, and ecology of the Rangia and marsh clams as well as their harvests and marketing as food. The information was obtained from the literature and by interviewing clam industry fishermen, processors, managers of cooperatives, and government technicians, and by photographing relevant scenes in the States of Tamaulipas, Veracruz, Tabasco, and Campeche during 2004 and 2005.

Distribution, Biology, and Ecology

Rangia cuneata ranges from Chesapeake Bay, Maryland, to Mexico’s Terminos Lagoon, and R. flexuosa is found from Louisiana to Terminos Lagoon, while P. caroliniana ranges from Virginia to the State of Campeche (Abbott, 1974; Ruiz, 1975). The two Rangia species and P. caroliniana are present in at least 16 estuaries along Mexico’s Gulf Coast from the States of Tamaulipas to Campeche (Table 1). Their main production area is in the Alvarado Lagoon and other small lagoons and channels that are part of the lower Papaloapan River area. Minor harvesting takes place in the Mezcalapa Lagoon and Tamiahua Lagoon, both in Veracruz (Echeverria et al., 2002).

Rangia cuneata and P. caroliniana have about the same shell length, 3-7 cm, when harvested, while R. flexuosa is smaller, 2.5-4 cm (Garcia-Cubas, 1981). Their valves are hard, subtriangulate, and inequilateral; their color ranges from black to light brown or yellowish. Their periostracum is fibrous and is usually eroded near the umbos which have a salmon-pink color. The shell interior is bluish white and the dorsal part is pinkish, sometimes with purple spots. The pallial line is tenuous (Garcia-Cubas, 1981). In R. cuneata, the posterior lateral tooth is long (LaSalle and De la Cruz, 1985). Rangiaflexuosa is easily distinguished from R. cuneata by its short posterior lateral tooth (Garcia-Cubas, 1981). The three species occur in brackish waters. Rangia cuneata is most common in areas with salinities from 5-15[per thousand] (Swingle and Bland, 1974). Its habitats have high water turbidity and soft substrates that consist of a mixture of sand, mud, and vegetation (Tarver, 1972). Its highest concentrations are in shallow areas less than 6 m deep. A decrease in density has been observed as depth increased from 2.5 to 4.6 m (LaSalle and De la Cruz, 1985). The two Rangia species inhabit subtidal zones, whereas P. caroliniana occurs in intertidal areas and in relatively small numbers in the shallow nearshore areas.

The feeding of R. cuneata and P. caroliniana is suspensivore and saprophytic, while R. flexuosa is microphagous, suspensivore, and saprophytic (Olsen, 1973, 1976; Garcia-Cubas, 1981). Rangia cuneata appears to obtain organic matter and phosphate from sediments by direct ingestion or by feeding on bacteria associated with the materials (Tenore et al., 1968).

In some zones of the Alvarado Lagoon, the mean density of R. cuneata was about 29/[m.sup.2]; R. refluosa, 34/[m.sup.2]; and P. caroliniana, 15/[m.sup.2] (Morales and Cruz Suares, 2000). In Mezcalapa Lagoon, the R. cuneata density was 15/[m.sup.2] and P caroliniana was 15/[m.sup.2] (Morales, 2004). The densities are lower than those reported in the United States, where harvesting does not occur: R. cuneata had a density of 26/[m.sup.2] in Lake Pontchartrain, Louisiana (Abadie and Poirrier, 2000); and 100/[m.sup.2] in a Mississippi marsh (Duobinis-Gray and Hackney, 1982). The lower densities in MExico may be due to commercial harvesting there.

In Alvarado Lagoon, R. cuneata spawn year-round, but mostly from February-July (Echeverria and Rodriguez, 1993). In Pore Lagoon, Campeche, where temperatures range from 22.0 to 30.5[degrees]C and salinities in summer are from 0 to 3 [per thousand], their spawning is during February-June and September–November (Rogers and Garcia-Cubas, 1981; Ortega-Salas, 1992).

During the summer rainy season, fresh water from coastal swamps enters Alvarado Lagoon and can reduce the salinity to nearly zero causing some of the clams to die (Garcia (1)). The epibiota on any clam shells lying on sediment surfaces include mollusks, barnacles, and tubicular polychaetes.

In Mexico, R. cuneata is preyed upon by fish, including blue catfish, Ictalurus furcatus; freshwater drum, Aplodinotus grunnieus; spot, Leiostomus xanthurus; and also blue crabs, Callinectes spp., river shrimp, Macrobrachium spp., gastropods (including moon snails, Polinices spp.), and ducks, family: Anatidae. Within its overall range in the United States and Mexico, R. cuneata is eaten by at least 17 fish species, 2 crab species, 2 gastropod species, and 8 duck species (references cited in LaSalle and De la Cruz, 1985).

Historical Uses

Prehispanic people in southeastern Mexico used the meats of the clams for food and their shells as construction material (Stark, 1977, 2001; Stark (2)). Ethnographers have noted the use of the clams as the primary material of cement in southern Veracruz (Stark (2)). Jimenez Badillo (1991) found evidence that the shells of R. flexuosa and P caroliniana were carried inland and used as offerings in the Templo Mayor (main temple) of Tenochtitlan (prehispanic Mexico City).

In recent decades, the clams have been harvested at least lightly along the entire coast from Laguna Madre in Tamaulipas to Terminos Lagoon in Campeche (Baqueiro and Echevarria, 1997), but currently nearly 99% of the commercial landings are from Alvarado Lagoon. In the early 1980’s, Pom Lagoon, Campeche, was the major clam producing area, but its stocks have declined in abundance. Sediments in Pom Lagoon range from silty sand to silty clay.

In Pom Lagoon, clams were harvested from boats with scrape (dip) nets, which consisted of a wooden pole 3-5 m long that had at one end a rectangular metal frame with attached mesh bag. The frame was 50 cm wide and 20 cm high; the mesh size was 1.5 cm (Fig. 3). To gather the clams, the fishermen anchored their boats, and pushed their scrape nets 1015 cm into the soft bottom, then pulled the nets toward themselves through the sediments, lifted the nets, rinsed out the sediments, and finally brought them into the boats and emptied the clams into containers (Fig. 4, 5).


After the fishermen harvested like this for several years, the clams became scarcer. To maintain their catches, the fishermen modified their method by pushing the scrape nets into the bottom sediments, tying the end of the poles to their boats, and dragging them behind for several minutes to fill the nets with clams (Baqueiro and Echeverria, 1997). In 1981, about 310 people harvested R. cuneata in Campeche (Uribe-Martinez, 1983). Since the middle of the 1990’s, the State of Veracruz has far exceeded Campeche in clam landings.

Current Harvesting Gear and Methods

About 450 people are licensed to harvest clams in Alvarado Lagoon (personal commun. SAGARPA). The numbers who actually harvest in any one day are undocumented. Most harvesters are men, 18-50 years old, but some women and children harvest also. Nearly all clam fishermen work individually, as few belong to cooperatives. They have relatively low incomes, about 200 pesos (US$18.75)/day.

Fishermen go to and from the Alvarado Lagoon harvesting beds in wood and fiberglass boats. The boats, about 7.6 m long, are propelled by 45-60 hp outboard motors, and each carries up to nine fishermen. Clam buyers share boat expenses (costs of motors and fuel) with the fishermen.

Fishermen know the locations where each of the clam species is most abundant, and they harvest the species requested by the buyer. Harvests are by hand picking. The fishermen cover their fingers with small latex balloons to protect them against cuts from shells (Fig. 6). They leave their boats to wade in the water and feel for the clams in the bottom sediments with their fingers (Fig. 7). The clams are placed in floating plastic boxes tethered with a thin line to the clammers’ waists (Fig. 8). They harvest each day for about 5 h (usually from about 9 a.m.-2 p.m.). Each gathers about 60 kg (1,500 clams)/day (Garcia (1)). Fishermen sort the clams, putting the R. cuneata, R. flexuosa, and P. caroliniana into separate bags on board the boats before they arrive ashore (Fig. 9, 10, 11). The largest harvests are between September and February. They decrease after the lenten season, because the demand for clams falls.

[FIGURE 6-11]

In the De La Costa Lagoon, Tamesi River, and Chairel Lagoon near Tampico, Tamaulipas, two or three fishermen harvest clams for sale (Fig. 12, 13). In this area, the most common species harvested is P. caroliniana.


Landing Statistics

Official statistics gathered by Mexico’s Federal government lump together all the clam species (3) (Mackenzie et al., 2002), and therefore landings of the different species of brackish water clams cannot be determined (Fig. 14). Pech et al. (1995) reported that the landings composition in Alvarado Lagoon were about 50% R. cuneata, 33% R. flexuosa, and 17% P. caroliniana. During the period 1985-2002, annual production of clams ranged from 624 to 2,945 t, with an average of 1,299 t. Campeche landings fell from 1,389 t/year to less than 100 t/ year from 1985 to 2002, while Veracruz landings increased from an average of 377 t/year during 1985-1988 to 1,389 t/ year during 1990-1992.


The production decline in Campeche may have been caused by increased harvest owing to the Mexican government raising harvest quotas from 20 to 34 t/week. The market-sized clams may have been depleted. Besides harvesting, though, environmental changes that resulted from bottom dredging when a gas pipeline was installed in the Pom Lagoon may have been partly responsible for the reduced abundance of the clams in Campeche (Solis-Ramirez, 1994; Baqueiro and Echeverria, 1997). Similar abundance declines of R. cuneata occurred in other estuaries where shell dredging or construction and improvements of deepwater navigation channels have taken place (Harrel, 1993; Abadie and Poirrier, 2000).


Rangia and marsh clams have a muddy taste and thus people do not eat them often. Fishermen’s families eat them about once a week. The clams are prepared in soups containing boiled rice and in cocktails (Garcia (1)). The soups may also include blue crabs, shrimp, oysters, fish, or squid, besides the clams. This is a traditional food preparation in Alvarado and has the name, “arroz a la tumbada.”

Nearly all the harvested clams are trucked to Mexico City, while small quantities are distributed to markets in Veracruz City and in towns nearby in Veracruz (Morales (4)). Brackish water clams are sold in the shell by weight. Buyers prefer R. cuneata with shell lengths of 2-5 cm. In 2004, buyers paid fishermen 8.00-10.00 pesos (US$0.70-0.86)/kilo(25-30 clams) for R. cuneata and 1.50-2.00 pesos (US$0.13-0.17)/ kilo(30-40 clams) for R. flexuosa and P. caroliniana (20-30 clams). The clams are sold in food markets and outdoor fish markets in Mexico City. Rangia cuneata are sold to the wholesale trade for 18.28 pesos (US$1.60)/kilo whereas R. flexuosa and P. caroliniana sell for 7.15 pesos (US$0.62)/kilo (Anonymous (5)). In public markets, R. cuneata frequently sell for 18-25 pesos (US$1.55-2.20)/ kilo, while R. flexuosa and P. caroliniana sell for 6-9 pesos (US$0.68-0.70) (SLIM, 2004). In markets in Ciudad Del Carmen, Tabasco, and Veracruz City, marsh clams sell for 11.1-13.9 pesos (US$0.90-1.25)/kilo. The price of a typical plate of seafood soup with rice, including four clams with other fish products, is about 60 pesos (US$5.22) in a restaurant in the city of Alvarado, Veracruz. The clams are used also in preparing “paella,” a traditional Spanish-culture dish.

Future Prospects

The Mexican Government increased its financial support of fishermen groups to carry out development projects begin ning in 2003. Clam fishermen are encouraged to propose ideas and marketing strategies to increase their incomes. The goal is to improve economic conditions in the fishing villages.

More information is needed about the ecology of the brackish water clams as an aid in increasing and maintaining their production. Future research should concentrate on a better understanding of 1) conditions surrounding recruitment, 2) predation upon the clams, and 3) the ecological requirements of each clam species. Clam production might be increased by making population-abundance surveys in all the coastal lagoons, to determine whether high abundances of clams are present in them.

Southern Quahog Fishery

Southern quahogs also occur in some of the same estuaries as the Rangia and marsh clams, but only in high salinity areas (MacKenzie et al., 2002). They are most abundant in Laguna Madre, Tampamachoco Lagoon, Carmen Lagoon, Tupilco Lagoon, Mecoacan Lagoon, Terminos Lagoon, and near Isla Arena. They are harvested on a commercial scale mainly in Carmen Lagoon. Fishermen harvest them at wading depths. They feel for the quahogs with their feet, collect them by hand, and place them in plastic boxes that are floated by empty soda bottles and Styrofoam similar to those used in the Rangia and marsh clam fishery. Each fisherman usually gathers 200-250 quahogs/day. The quahogs are sold whole and then shipped by truck on a small scale to various cities, where they usually are served in cocktails, in soups, or in their shells after being broiled.


We thank Alejandro Gonzalez Cruz and Rodolfo Morales for their help as guides in tours of clamming areas and for providing information, Victor Rivera Roman for providing photographs, Victor G. Burrell, Jr., Dexter S. Haven, and Fernando T. Wakida, for useful comments on earlier drafts of the manuscript, and the other people who provided information.

(1) Garcia M., S. Clam fisherman, Alvarado, Vera-cruz. Personal commun., July 2004.

(2) Stark, B. L. Professor, Arizona State University, Personal commun., March 2004.

(3) CONAPESCA. 2002. Anuario estadistico de pesca. SAGARPA (Secretaria deAgricultura, Ganaderia, Desarrollo Rural, Pesca y Alimentacion). http://www.sagarpa.gob.mx/conapesca/planeacion/anuario2002.

(4) Morales, R. Technician, Centro Regional de Investigacion Pesquera, Veracruz. Personal commun., July 2004.

(5) Anonymous. 2004. Mollusks, cephalopods y rajas congealed, www.infopesca.org/libres/info102004/Moluscos.pdf

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Table 1.–Mexican lagoons where brackish water clams are reported.


State/lagoon water clams References


San Andres PC (1) Covarrubias, 1988; Garcia-Cubas

et al., 1990a

Chairel and PC Personal observation

Tamesi River


La Costa PC Segura, 1980

Pueblo Viejo RF (2), PC Reguero and Garcia-Cubas, 1993

Tamiahua RC (3), RF Garcia-Cubas, 1978; Gomez, 1984;

Arroyo et al., 1985; Arroyo and

Ortega, 1987; Portilla, 1989;

Echeverria et al., 2002

Tampamachoco RF, RC Reguero et al., 1991; Flores and

Garcia-Cubas, 1986

La Mancha RF Flores-Andolais et al., 1988

Chica and Grande RF Garcia-Cubas et al., 1992

Camaronera RF, RC Reguero and Garcia-Cubas, 1991

Alvarado RF, RC, PC Reguero and Garcia-Cubas, 1989;

Echeverria et al., 2002

Sontecomapan RC, RF Garcia-Cubas and Reguero, 1995

Mezcalapa RC, PC Echeverria et al., 2002; Morales,



Carmen-Machona RF, RC, PC Antoli and Garcia-Cubas, 1985

Tupilco-Oston RF Garcia-Cubas and Reguero, 1990

Mecoacan RF, RC Garcia-Cubas et al., 1990b


Terminos system: RC, RF, PC Garcia-Cubas, 1981

Pom, del Este,

Balchacan, and


(1) PC= Polymesoda caroliniana.

(2) RF=Pangia flexuosa.

(3) RC=Pangia cuneata.

Armando T. Wakida-Kusunoki is with the Instituto National de la Pesca, Ave. Heroes del 21 de Abril s/n, Col. Playa Notre, Cd del Carmen, Campeche. C.P. 24120. Mexico. (e-mail: armandowakida@yahoo.com.mx), and Clyde L. MacKenzie, Jr., is with the James J. Howard Marine Science Laboratory, Northeast Fisheries Science Center, National Marine Fisheries Service, NOAA, 74 Magruder Road, Highlands, NJ 07732.

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