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-Rhode Island fi shermen in their rowboats harvesting quahogs with bull rakes, late 1940's (from Tressler and Lemon, 1951).
Source publication
The northern quahog, Mercenaria mercenaria, ranges along the Atlantic Coast of North America from the Canadian Maritimes to Florida, while the southern quahog, M. campechiensis, ranges mostly from Florida to southern Mexico. The northern quahog was fished by native North Americans during prehistoric periods. They used the meats as food and the shel...
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Context 1
... and harvested quahogs with tongs (Desbonnet and Lee, 1991). By the early 1900's, some fi shermen were towed to the beds by motor boats (Boyd, 1991), and by the late 1930's many had their own outboard motors to propel their boats. In the 1940's, when the oyster in- dustry in Narragansett Bay had declined, the quahog fi shery grew in importance (Fig. 10). During World War II, about 40 boats, 9-10.6 m long, using rocking chair dredges (Fig. 11), joined the tonging fl eet harvesting quahogs. Each dredging boat was limited by state regulation to 40 bu/ day. This fi shery ended in ...
Context 2
... system 30-45 days until they are retained on a 790µ screen (1-mm quahog). The 1-mm quahogs are moved to an upweller system and are fed ambient food (Fig. 97). Heretofore, the larvae had been fed cultured algae (Fig. 98-100). The quahogs in the upwellers are cleaned about 3 times a week. When they reach 2.4 mm they are moved to out- side upwellers (Fig. 101). They remain in this system until they reach 4-8 mm (about 8-12 weeks old, depending on season) and then are put in a fi eld nursery system. The field nursery system in warm months is made up of either one or two systems. One consists of 1 × 3-foot plastic mesh bags, stocked 5,000 seed per bag. The bags are placed in the in- tertidal ...
Citations
... 2002b). Historically, the states of Florida, Virginia, and Connecticut are the highest producers of molluscan shellfish (MacKenzie et al. 2002b), with Crassostrea virginica (the eastern oyster) and Mercenaria mercenaria (northern quahog) the two most frequently harvested species. Increased disease occurrence (i.e., Dermo), loss of habitat, and other environmental stressors have resulted in a decline in harvests of C. virginica since the 19th century (Mackenzie 1996). ...
... Increased disease occurrence (i.e., Dermo), loss of habitat, and other environmental stressors have resulted in a decline in harvests of C. virginica since the 19th century (Mackenzie 1996). This reduction in oyster production contributed to increased commercial harvest of northern quahog during the 1920s, which became a promising commercial enterprise, following the introduction of the hydraulic dredge (1958 in Connecticut) and seed hatcheries in the 1960s (Mackenzie et al. 2002b). As the dominant producer of northern quahog, the USA harvested over 4.1 million m.t. ...
... Water pressure is sufficient to remove clams without shell damage (Jolley 1972). Because hard clams grow slowly, cultivated shellfish beds are dredged every 3-5 years to allow clams to reach harvestable sizes (MacKenzie et al. 2002a(MacKenzie et al. , 2002b. The use of towed fishing gear elicits some concerns because of potential damage to non-target benthic organisms, chronic effects to diversity in the dredge track, and potential biogeochemical changes in the sediments (Levy 1998;Watling and Norse 1998;Watling 2005). ...
A before-after-control-impact (BACI) experiment was conducted to examine the effects of hydraulic clam dredging on sediment biogeochemistry of a leased shellfish bed of Mercenaria mercenaria, northern quahog, over the course of an entire growing season. Six study plots (0.67 ha each), three dredged and three not dredged, off of Milford, Connecticut, in Long Island Sound, were sampled from May to October 2009 for porewater fluxes of total ammonia, oxygen, and hydrogen. Particulate samples were also analyzed for grain size, total nitrogen, total carbon, total sulfur, and organic carbon. Statistical analysis indicated no significant difference between dredged and not dredged sites. Grain size and oxygen flux explained 22% of the variation in the total benthic species assemblages; grain size and either total carbon or organic nitrogen explained 18% of the variation in molluscan abundance. Our study demonstrates that one-time hydraulic shellfish harvesting had minor effects on the sediment chemistry of a leased clam bed.
... The long history of eutrophication, contamination by sewage, and commercial fishing in LIS is documented with core data (ten Brink et al., 2000;Thomas et al., 2000) and historical fishing records (Getchis, 2005;MacKenzie et al., 2002). Anthropogenic eutrophication, driven by the addition of nitrogen from wastewater treatment plant effluent, is a function of human population density and increases from east to west toward New York City (ten Brink et al., 2000) resulting in a gradient in bottom water dissolved oxygen (DO) during the summer (Fig. 1). ...
Benthic communities in Long Island Sound (LIS) have experienced over 150 years of commercial shellfishing and excess nutrient loading (eutrophication) which causes hypoxia. We established an ecological baseline using a combination of live, dead, archaeological, and fossil material to investigate the impacts of these stressors on the molluscan community. We expected that ecological change would increase with eutrophication-hypoxia west towards New York City. Instead we found that taxonomic similarity, rank-order abundance, and drilling frequency are more strongly controlled by commercial fishing pressure than by decreasing dissolved oxygen. Commercial fisherman collecting quahog clams (Mercenaria mercenaria), physically disrupt surface-dwelling organisms and also kill large numbers of predatory gastropods, including the channeled whelk, Busycotypus canaliculatus, and the drilling moonsnails Neverita duplicata and Euspira heros, to protect hard clam stocks. As a result, areas dredged by commercial fishermen yield fewer shells with drill-holes and fewer surface-dwelling organisms than unfished sites. In spite of recent reductions in lobster fishing, crushing predation by crabs and lobsters on clams has been suppressed below baseline levels throughout LIS, even in the well oxygenated east. The absence of a clear relationship between eutrophication-hypoxia and ecological change questions the effectiveness of nitrogen reduction alone as a restoration strategy. LIS fossils revealed a relatively ancient loss of those mollusks associated with seagrass and oyster habitats (e.g., oysters, Crassostrea virginica; jingle shells, Anomia simplex; scallops, Argopecten irradiens; and the gastropod Bittiolum alternatum) that predates the accumulation of dead shells and underscores the need for older material to reveal the shifting baseline. The interactive nature of multiple stressors means that past overfishing may have dampened the response of communities in LIS to eutrophication or inhibited their capactiy to recover. The unexpected role of hypoxic areas protected from commercial fishing as refuges highlights the utility of no-take marine preserves in eutrophied estuaries worldwide.
... In addition, they have been identified as strong indicators of estuarine health because they are relatively sedentary and therefore cannot avoid deteriorating water or sediment quality (Dauer 1993). Further, in regions like New England, where bivalve molluscs are culturally and commercially valuable (Belding 1909(Belding , 1930MacKenzie et al. 2002aMacKenzie et al. , 2002b, the reestablishment of diverse, abundant benthic molluscan communities is of special interest. ...
Historic human-imposed tidal flow restrictions at many New England estuaries have resulted in dramatic alteration of estuarine community structure and function. East Harbor, a 291-ha coastal lagoon and salt marsh in Truro, Massachusetts, was artificially isolated from Cape Cod Bay in 1868. After the isolation, salinity decreased to near freshwater levels, and estuarine fish and invertebrate populations declined precipitously. Partial tidal flow was restored to East Harbor in 2002; since then, East Harbor has experienced substantial increases in salinity, and native fauna has begun to return to the system. The objective of this study was to obtain information on marine molluscan populations recolonizing East Harbor. Using a combination of benthic cores and direct searching, we surveyed 50 plots throughout the estuary in July and August 2005. We detected 16 molluscan species in East Harbor as a whole; the four most abundant species were Mya arenaria, Littorina spp., Mytilus edulis, and Mercenaria mercenaria. We found significant differences in species richness and abundance of these species among three regions of East Harbor that varied markedly in salinity and distance to Cape Cod Bay; diversity and abundance were both highest in Moon Pond, which has a direct connection with sources of seawater and marine biota, and lowest in the northwest cove, which receives high freshwater discharge. These findings demonstrate the effectiveness of Cape Cod National Seashore’s preliminary tidal restoration efforts while underscoring the continued need for full tidal restoration at East Harbor and other tide-restricted estuaries.
... 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. ...
... Official statistics gathered by México'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)Solis-Ramirez, 1994; Baqueiro and Echeverria, 1997). ...
... 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. ...
Rangia and marsh clams, Rangia cuneata, R. flexuosa, and Polymesoda caroliniana, occur in brackish waters along México’s eastern coast from the northern State of Tamaulipas to the southern State of Campeche. The clams were important to the prehispanic people in the southern part of the State of Veracruz, where they were used as food and as construction material. In modern times, they are harvested for food. The fishermen wade in shallow water and harvest the clams in soft sediments by hand. Annual landings of whole clams during a recent 5-yr period, 1998–2002, were 1,139–1,695 t. The only area with a substantial ongoing clam fishery is in the Lower Papaloapan River Basin, including Alvarado Lagoon, where as many as 450 fishermen are licensed harvesters. This fishery for the Rangia and marsh clams is the most important clam fishery along México’s Gulf Coast.
We studied the effects on invertebrate infauna and grain size of harvesting northern quahogs Mercenaria mercenaria with a short rake. The substrate was a mixture of medium-coarse sand (phi values, 0.847–1.159) that was covered by 0.5 m of water at low tide. Two experimental areas (I + II) in Raritan Bay, New Jersey, were subdivided into six 5.5-m × 5.5-m plots. We raked alternate plots, the unraked plots serving as controls. In area I, we raked the treatment plots once (in June 2000) and then sampled all plots for effects on invertebrates and grain size. The number of invertebrates in the five taxa we counted and the mean grain size did not differ significantly (P > 0.05) between treatment and control. In area II, we raked the treatment plots three times, one month apart (in July, August, and September 2000) and then sampled all plots. The results for invertebrates and grain size were similar to those for area I. This study suggests that short raking once or repeatedly during a harvesting season in a shallow sandy substrate does not measurably alter numbers of invertebrates or sediment grain size.
We hypothesized that the decline in hard clam Mercenaria mercenaria populations since the 1970s in many of the south shore bays of Long Island, New York, USA, was due to changes in reproduction caused by variations in phytoplankton available as a food resource. We measured in 2000 and 2001 the reproductive condition of female clams from 5 sites in south shore bays of Long Island and from 2 sites in New Jersey. Phytoplankton composition was measured as the concentration of total and size-fractionated chlorophyll a (chl a), particulate organic carbon (POC), and nitrogen (PON), and the abundance of the harmful picoplankter Aureococcus anophagefferens. Timing of peak hard clam reproduction was nearly identical across sites, and was the same as in archived samples of clams collected in 1978 and 1979. Hard clam condition index differed between sites, with poorest condition being exhibited at the 3 Great South Bay (GSB) sites. There were also appreciable differences in relative reproductive output between locations, with clams again from the 3 GSB sites having the lowest estimated egg production. The central and eastern GSB had the highest levels of total chl a, POC, and PON, however, of any south shore bay, although this was mainly contributed by cells <2 mu m, which have low nutritional value for adult hard clams. In addition, the 3 sites in GSB suffered brown tide blooms during 2000 and 2001, which are known to inhibit bivalve feeding. We conclude that changes in the composition of the phytoplankton community at some locations may be reducing hard clam reproductive output.
