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VIMS Articles

Oyster

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A Comparison Of Methods For Calculating Condition Index In Eastern Oysters Crassostrea Virginica (Gmelin, 1791), Roger L. Mann Jan 1992

A Comparison Of Methods For Calculating Condition Index In Eastern Oysters Crassostrea Virginica (Gmelin, 1791), Roger L. Mann

VIMS Articles

A number of techniques have been reported to estimate condition index in oysters and other bivalve molluscs. We report and compare condition index, estimated by three different methods, for oysters collected from a single reef in the James River, Virginia over a four week period in the summer of 1987. Two indices express condition as a ratio of dry meat weight to shell cavity volume, but differ in methods of estimating shell cavity volume. A third method expresses condition as a ratio of dry meat weight to dry shell weight. Within the size range 36-96 mm length there is no ...


Effects Of Perkinsus Marinus Infection In The Eastern Oyster, Crassostrea Virginica: Ii. Disease Development And Impact On Growth Rate At Different Salinities, Kennedy T. Paynter, Eugene M. Burreson Jan 1991

Effects Of Perkinsus Marinus Infection In The Eastern Oyster, Crassostrea Virginica: Ii. Disease Development And Impact On Growth Rate At Different Salinities, Kennedy T. Paynter, Eugene M. Burreson

VIMS Articles

In order to assess the impact of Perkinsus marinus infection on oyster growth and mortality, oysters were raised in floating rafts at six sites around Chesapeake Bay. The sites were comprised of two low salinity sites (8-10%0), two moderate salinity (12-15%0) sites and two high salinity sites (16-20%0). Oyster growth was monitored biweekly along with various water qualities including temperature and salinity. Condition index was measured monthly and disease diagnosis was perfonned bimonthly. Oyster growth was initially greatest at the high salinity sites but was subsequently retarded by Perkinsus infection at both the moderate and high salinity ...


The Decline Of The Virginia Oyster Fishery In Chesapeake Bay Considerations For Introduction Of A Non-Endemic Species, Crassostrea Gigas (Thunberg, 1793), Roger L. Mann, Eugene M. Burreson, Patrick K. Baker Jan 1991

The Decline Of The Virginia Oyster Fishery In Chesapeake Bay Considerations For Introduction Of A Non-Endemic Species, Crassostrea Gigas (Thunberg, 1793), Roger L. Mann, Eugene M. Burreson, Patrick K. Baker

VIMS Articles

The Chesapeake Bay oyster fishery for Crassostrea virginica (Gmelin) is in a state of continuing decline. Two diseases, Haplosporidium nelsoni and Perkinsus marinus have effectively eliminated oysters from many sections of the Bay. Despite over 30 years of disease activity the native oysters have developed neither tolerance nor absolute resistance to these diseases, and do not exhibit any recovery in disease endemic areas in Virginia. Repletion programs have completely failed to recover to permanent production areas lost to disease. Present fishery management activities are limited to a controlled retreat away from the disease in an arena where disease distribution is ...


Settlement Patterns Of Crassostrea Virginica (Gmelin, 1791) Larvae In Relation To Tidal Zonation, G. Curtis Roegner, Roger L. Mann Jan 1990

Settlement Patterns Of Crassostrea Virginica (Gmelin, 1791) Larvae In Relation To Tidal Zonation, G. Curtis Roegner, Roger L. Mann

VIMS Articles

Experiments were conducted to determine the settlement distribution of the oyster Crassostrea virginica (Gmelin) in relation to tidal zonation in an area where adult populations are largely confined to the intertidal zone. Hatchery-reared pediveliger larvae were interned in PVC tubes positioned at known tidal heights. The influence of non-tidal factors was limited: mesh covering the ends of the tubes prevented loss of larvae to dispersal or predation, the settling substrate was not colonized by competitors, and the effects of light and horizontal currents were minimized. Settlement was found to occur throughout the intertidal zone but predominated at the bottom of ...


Effect Of Decreasing Oxygen Tension Of Swimming Rate Of Crassostrea Virginica (Gmelin, 1791) Larvae, Roger L. Mann, Julia S. Rainer Jan 1990

Effect Of Decreasing Oxygen Tension Of Swimming Rate Of Crassostrea Virginica (Gmelin, 1791) Larvae, Roger L. Mann, Julia S. Rainer

VIMS Articles

Four sizes of Crassostrea virginica Gmelin larvae (mean lengths 76.8, 118.1, 139.7 and 290.2 [Lm) were exposed to ·stepwise decreases in oxygen concentration from I 00% saturation (5 .38 mill at 22°C and 22 ppt salinity) to as low as 10% saturation and their swimming rates (net vertical movement per unit time) were recorded at each oxygen concentration. No cessation of swimming was observed and in only two conditions, that of 76.8 [Lm larvae at 10% saturation and 290.2 j.Lm larvae at 21% saturation, was swimming rate significantly lower than that of ...


Development And Evaluation Of Techniques To Study Acquired Immunity To Perkinsus Marinus In The Oyster, Crassostrea Virginica (Gmelin), Fu-Lin Chu Jan 1988

Development And Evaluation Of Techniques To Study Acquired Immunity To Perkinsus Marinus In The Oyster, Crassostrea Virginica (Gmelin), Fu-Lin Chu

VIMS Articles

This paper describes a radiometric technique developed to measure phagocytosis of Perkinsus marinus zoospores by oyster hemocytes. The spores of P. marinus were radiolabeled by culturing P. marinus presporangia and sporangia in estuarine water (22%o) containing 14C-glycine. The percent of spores phagocytized by hemocytes was determined by the uptake of radioactivity by hemocytes.

Results from preliminary experiments to test the efficiency of using an osmotic infiltration method for immunizing oysters are also reported. It was found that oysters can take up both dissolved antigen (radiolabeled bovine serum albumin) and particulate antigen ( 14C-labeled zoospore homogenate) through osmotic infiltration. The uptake ...


A Comparison Of Paraffin Histology And Hemolymph Analysis For The Diagnosis Of Haplosporidium Nelsoni (Msx) In Crassostrea Virginica (Gmelin), Eugene M. Burreson, M.Elizabeth Robinson, Antonio Villalba Jan 1988

A Comparison Of Paraffin Histology And Hemolymph Analysis For The Diagnosis Of Haplosporidium Nelsoni (Msx) In Crassostrea Virginica (Gmelin), Eugene M. Burreson, M.Elizabeth Robinson, Antonio Villalba

VIMS Articles

Diagnosis of the oyster pathogen Haplosporidium nelsoni (MSX) by paraffin histology is compared with a technique in which hemolymph drawn from the oyster adductor muscle sinus is examined for parasite plasmodia. Oysters from seed beds of the James River, Virginia imported to an MSX endemic area in May, 1986 were sampled monthly through December, 1986 and in February, 1987. A sample of 25 oysters was bled each month and then processed for sectioning. Of the 200 oysters sampled, 89 (44.5%) were diagnosed as infected using histology and 61 (30.5%) were diagnosed as infected using hemolymph examination. All the ...