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  • Venus bucardium  Born, 1780
  • Arctica vulgaris  Schumacher, 1817
  • Cyprina islandica var. crassior  Jeffreys, 1864: p. 305.
    FAO Names
    En - Ocean quahog, Fr - Cyprine d'Islande, Sp - Almeja de Islandia.
    3Alpha Code: CLQ     Taxonomic Code: 3160904501
    Scientific Name with Original Description
    Venus islandica  Linnaeus, 1767. Systema naturae Ed. 2, reformato, v. 1, pars. 2, Classis VI. Vermes. Holmia p. 1131: 533-1327. Type locality: Iceland
    Diagnostic Features
    Shell thick and strong, broadly oval, with prominent umbones.  The periostracum peels away on dead shells, revealing a white to pale brown shell beneath. Anterior hinge line strongly curved, lunule ill-defined. Escutcheon shallow, occupied by thick, aeched, brown or black ligament. Sculpture of concentric lines and few irregular grooves. Right valve with three prominent cardinal teeth and single posterior lateral tooth; triangular pit in front of anterior cardinal, surrounded by small knobs and ridges. Left valve with three cardinals and one posterior lateral, anterior cardinal continuous with series of small ridges and denticulations. Inner surfaces smooth, glossy; adductor scars distinct, posterior slighty larger than anterior. Ventral margin crenulate (Hayward et al., 1990).  It has a thick glossy periostracum that is brown in smaller individuals, becoming greenish-brown to black in larger specimens. 
    Geographical Distribution
    The ocean quahog is a bivalve mollusk found in temperate and boreal waters on both sides of the North Atlantic. It is distributed on the continental shelf from Newfoundland to Cape Hatteras (Weinberg 1995). Greatest concentrations are in offshore waters outh of Nantucket to the Delmarva Peninsula (Serchuk et al. 1982). The inshore limit of their distribution appears to be defined by the 16°C bottom isotherm in the summer months (Mann 1989). They are found in relatively shallow water in eastern Maine (but never intertidally) and in deeper, more offshore waters south of Cape Cod (MAFMC 1997).
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    Habitat and Biology
    Although the species has been found at depths of 14-82 m, most are found at depths of 25 to 61 m (Serchuk et al. 1982). Juvenile ocean quahogs are found offshore in sandy substrates (Kraus et al. 1992). Adult ocean quahogs are usually found in dense beds over level bottoms, just below the surface of the sediment which ranges from medium to fine grain sand (MAFMC 1997).Larvae are planktotrophic. Adult ocean quahogs are suspension feeders on phytoplankton, using their relatively short siphons which are extended above the surface of the substrate to pump in water.
    Ocean quahogs mature very slowly. Rowell et al. (1990) report the mean age of sexual maturity for Nova Scotian quahogs to be 13.1 years for males and 12.5 years for females. The earliest age of maturity was 7 years for both sexes, and maturity occurred at about 49 mm shell length. Ocean quahog spawning is protracted, lasting from spring to fall. Extended spawning period, from May through December, with several peaks during this time. Multiple annual spawnings may occur at the individual and population levels (Mann 1982). The eggs and larvae of ocean quahogs are planktonic (MAFMC 1997).  Found at oceanic salinities and restricted to cooler waters where temperatures rarely exceed 20°C. Based on field distributions on both sides of the Atlantic, Golikov & Scarlato (1973) estimated the optimal temperature for ocean quahogs to be 6-16°C. They are capable of surviving low dissolved oxygen levels.  The ocean quahog is among the longest-lived and slowest growing of marine bivalves and may reach a maximum age of 225 years (MAFMC 1997).
    Up to 120 mm shell length.
    Interest to Fisheries
    The principal gear used in the fishery is the hydraulic clam dredge. Until the early 1990s, most ocean quahogs were caught off New Jersey and the Delmarva peninsula. The fishery has been moving north for several years and significant catches are now taken off Long Island and southern New England (Weinberg, 2001). FAO's Yearbook of Fishery Statistics reports a range of yearly production from around 185881 mt in 1995 to 147933 mt in 1999 (Canada, Norway, USA, Iceland).
    Golikov, A.N. & O.A. Scarlato - 1973. Method for indirectly defining optimum temperatures of inhabitancy for marine cold-blooded animals. Mar.Biol. .  20: 1-5..
    Hayward, P. J., Wigham, G.D. & Yonow, N. - 1990. Mollusca I: Polyplacophora, Scaphopoda, and Gastropoda. In: The marine fauna of teh British Isles and North-West Europe, Vol. 2. Molluscs to Chordates. P.J. Hayward & J. S. Ryland (Eds). Clarendon Press, Oxford . 
    Kraus, M.G., B.F. Beal, S.R. Chapman & L. McMartin - 1992. A comparison of growth rates in Arctica islandica (Linnaeus, 1767) between field and laboratory populations. J. Shellfish Res. .  11: 289-294..
    L. M. Cargnelli, S. J. Griesbach, D. B. Packer & E. Weissberger - 1999. Ocean Quahog, Arctica islandica, Life History and Habitat Characteristics. NOAA Technical Memorandum NMFS-NE series, Nº 148 .  15 pp..
    MAFMC: Mid-Atlantic Fishery Management Council - 1997. Amendment #10 to the Fishery Management Plan for Atlantic surfclam and ocean quahog fisheries. MAFMC. March 1997. Dover, DE. .  58 p. + appendices..
    Mann, R. - 1982. The seasonal cycle of gonadal development in Arctica islandica from the southern New England shelf. Fish. Bull. (U.S.) . .  80: 315-326..
    Mann, R. - 1989. Larval ecology of Arctica islandica on the inner continental shelf of the eastern United States. J. Shellfish Res. .  8: 464..
    Rowell, T.W, D.R. Chaisson & J.T. McLane - 1990. Size and age of sexual maturity and annual gametogenic cycle in the ocean quahog, Arctica islandica (Linnaeus, 1767), from coastal waters in Nova Scotia, Canada. J. Shellfish Res. .  9: 195-203..
    Serchuk, F.M., S.A. Murawski & J.W. Ropes - 1982. Ocean quahog Arctica islandica. In M.D. Grosslein and T.R. Azarovitz eds. Fish distribution. .  p. 144-146..
    Weinberg, J. - 1995. Ocean quahog. In Conservation and Utilization Division, Northeast Fisheries Science Center eds. Status of the fishery resources off the northeastern United States for 1994. NOAA [National Oceanic and Atmospheric Administration] Tech. Mem. NMFS-NE-108. .  p. 121-122..
    Weinberg J. - 2001. Ocean Quahog. In: Status of fishery resources off the Northeastern United States for 1998. NOAA [National Oceanic and Atmospheric Administration] Tech. Memo. NMFS-NE-115. .  149p..
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