Life Sciences Commons^™

The Role Of Dietary Highly Unsaturated N-3 Fatty Acids In Northern Quahogs, Mercenaria Mercenaria, Through Decreasing Temperature, Sixto E. Portilla

Dissertations, Theses, and Capstone Projects

The series of investigations described in this thesis were designed to assess the effect of diet on mortality through decreasing temperature in two genetic varieties of M. mercenaria important to the natural environment and the aquaculture industry: “wild” from natural stocks and “notata” selected for fast growth. Data from these novel investigations demonstrate a temperature specific sensitivity to each dietary component designating 20:5n-3 as homeoviscously favorable in the upper thermal range above 12°C, and 22:6n-3 as favorable in the lower. Statistical analyses of variance demonstrate distinct cumulative mortalities among the 5 dietary treatments (P < 0.05) for each genetic variety at each thermal range, upper (>12°C) and lower (2 = 0.9326 …

Gonadal Cycle Of Northern Quahogs, Mercenaria Mercenaria (Linne, 1758), From Fished And Non-Fished Subpopulations In Narragansett Bay, Dora Marroquin-Mora, Michael Rice

Michael A Rice

To determine if population density in areas closed to fishing in Narragansett Bay is causing differences in the reproductive potential of the organisms, this study used two approaches to determine the reproductive condition of the animals. The first approach consisted in employing a gravimetric condition index (CI) to evaluate the general condition of quahogs from nine different sites, 3 sites open conditionally for fishing (conditional areas) and 6 sites closed to fishing. The second approach was a determination of gonadal index (GI) of a subset of the sample sites, by histological observation of gonadal tissue sections. Initial sampling included determination …

A Review Of Shellfish Restoration And Management Projects In Rhode Island, Michael A. Rice, April Valliere, Angela Caporelli

Michael A Rice

Shellfish management and restoration efforts in Rhode Island date back to the 19th century. From the late 1890s to the Second World War the Rhode Island Fisheries Commission operated a lobster hatchery in Wickford Harbor in response to a perceived decline in lobster catches in Narragansett Bay. Berried lobsters were collected, eggs hatched, larvae reared, and postlarval fifth stage juveniles were released into the bay. The project was discontinued primarily because of costs and a failure to demonstrate the efficacy of juvenile seeding in improving lobster catches. From the 1930s to the 1980s, there have been several similar efforts to …

Uptake Of Dissolved Free Amino Acids By Northern Quahogs, Mercenaria Mercenaria, And Its Relative Importance To Organic Nitrogen Deposition In Narragansett Bay, Rhode Island, Michael A. Rice

Michael A Rice

Studies were undertaken to determine the relationship between size of northern quahogs Mercenaria mercenaria and the rate at which they transport aspartic acid. Quahogs ranging from 25 to 103 mm valve length were collected in Narragansett Bay and placed in seawater aquaria (27 ppt, 20 deg C) and allowed to pump actively. Uptake experiments were carried out using 1 umol/L C(14) radiolabeled aspartic acid. Aspartate transport rates in umol/h can be related to valve length by the allometric equation with a = 24.32 and b = 0.905 when valve length is in mm. In May 1990, near bottom samples of …

Observations Of A Protistan Disease Similar To Qpx In Mercenaria Mercenaria (Hard Clams) From The Coast Of Massachusetts, Roxanna Smolowitz,, Dale Leavit, Frank Perkins

VIMS Articles

During the summer and fall of 1995, in clam aquaculture leases at two locations on the coast of Massachusetts, significant mortalities were observed to occur primarily in 112" role="presentation" style="font-size: 0.9px; display: inline-block; position: relative;">- to 2-year old hard clams (Mercenaria mercenaria,quahog) planted in the leases. Examination of hard clams from those leases suggested a parasite similar to QPX (Quahog Parasite Unknown), as described by Whyte, S. K., Cawthorn, R. J., and McGladdery, S. E. (1994,Can. Dis. Ag. Org.19, 129–136), was responsible for the poor condition of affected clams and the resulting high mortality. In …

A Review Of The Factors Influencing The Growth Of The Northern Quahog, Mercenaria Mercenaria (Linnaeus, 1758), Michael A. Rice, Jan A. Pechenik

Michael A Rice

Factors affecting the growth of larval, juvenile, and adult northern quahogs, Mercenaria mercenaria, are reviewed. Larval growth is affected by temperature, salinity, current speed, dissolved oxygen concentration, and the amount of suspended sediments in the water, along with such nutritional factors as food quantity and quality. Growth of post-set juvenile and adult quahogs is similarly affected by the same physical and nutritional factors. Recent work suggests that there is a strong genetic contribution to quahog growth rate and that selective breeding programs may be useful for producing rapid growth strains. A growing body of evidence suggests that larval growth rates …

The Northern Quahog: The Biology Of Mercenaria Mercenaria, Michael Rice

Michael A Rice

A general overview of the biology, fisheries and aquaculture of the northern quahog, Mercenaria mercenaria.

Biological Control Of Crab Predation On Hard Clams Mercenaria Mercenaria (Linnaeus, 1758) By The Toadfish Opsanus Tau (Linnaeus) In Tray Cultures, Robert Bisker, Michael Castagna

VIMS Articles

Oyster toadfish Opsanus tau (Linne) were tested as biological controls of crab predation on juvenile hard clams Mercenaria mercenaria (Linne) in trays with crushed stone aggregate. Clam survival after 34 weeks was 69.5% in the presence of toadfish and 2.3% in trays without toadfish. Toadfish reduced the total number of crabs (mud crabs and blue crabs). Crabs in trays with toadfish present had smaller carapace widths.

Predation By The Oyster Toadfish Opsanus Tau (Linnaeus) On Blue Crabs And Mud Crabs, Predators Of The Hard Clam Mercenaria Mercenaria (Linnaeus, 1758), Robert Bisker, Mary Gibbons, Michael Castagna

VIMS Articles

The oyster toadfish, Opsanus tau (Linne), reduces predation by xanthid and portunid crabs on juvenile hard clams, Mercenaria mercenaria (Linne), in field cultures. This study examined the influence of size and species on the predator-prey relationship between toadfish and crabs. The mud crabs Eurypanopeus depressus (Smith), Neopanope sayi (Smith), and Panopeus herbstii Milne Edwards of 5-40 mm carapace width and blue crabs Callinectes sapidus Rathbun of 77-105 mm carapace width were offered to toadfish of 70-322 mm total length. Toadfish predation rates on mud crabs were higher with increasing toadfish size and lower with increasing crab size. Toadfish injured or …

Effects Of Intensive Fishing Effort On The Population Structure Of Quahogs, Mercenaria Mercenaria (Linnaeus, 1758), In Narragansett Bay, Michael Rice, Charles Hickox, Itrat Zehra

Michael A Rice

Influx, Net Flux And Transepithelial Flux Of Amino Acids In The Hardshell Clam Mercenaria Mercenaria (Linne): Influence Of Salinity, Michael Rice, Grover Stephens

Michael A Rice

1.1. The effects of salinity on the uptake and internal distribution of alanine and other free amino acids (FAA) in hardsell clams, Mercenaria, was studied by radiochemical and high performance liquid chromatography (HPLC) techniques.2.2. Exposure of animals to reduced salinity does not alter the rate of unidirectional alanine influx.3.3. In 34%o salinity, entry of labeled alanine reflects the net flux of the amino acid. However, in 17%o salinity, there is a net loss of alanine and other acids, mainly taurine, to the medium.4.4. Reduced salinity induces greater incorporation of radiolabeled FAA into macromolecular fractions throughout the animal.5.5. The major factors …