Interaction Between Circulation of the Estuary of the James River and Transport of Oyster Larvae

Hydraulic model dye test results are examined to provide estimates of nontidal horizontal circulation and movement/retention of oyster larvae in the James River Estuary. Test conditions maintained a constant mean tide and average summer low freshwater discharge. It was assumed that movement of dye in the model would approximate movement of the planktonic (larval) stages of oysters (Crassostroa virginica) in the prototype. Test results were used to rank six dye release points (candidate brood stock locations) with respect to relative quantities of dye retained in areas of the model representing commercially important seed oyster beds during the period 20-40 tidal cycles after release (the time, after spawning, when oyster larvae will permanently attach to a suitable substrate). Under the test conditions, nontidal circulation in the model was similar to that found in a weak partially mixed estuary: upstream motion along the bottom and over the right hand shoals (looking upstream) and downstream motion elsewhere. The pattern was modified by cyclonic motion of surface waters in the upstream and downstream reaches which increased residence time of material in the seed oyster bed region. Greatest retention during the 20-40 tidal cycle period was from releases over upstream and right hand side shoals and is reflected in release point ranking.https://scholarworks.wm.edu/vimsbooks/1031/thumbnail.jp

The Effect of Tropical Storm Agnes on Oysters, Hard Clams, Soft Clams, and Oyster Drills in VIrginia

Tropical Storm Agnes had a major effect on the molluscan fisheries of Virginia. One effect was the direct mortality of oysters, Crassostrea virginiaa, in the upper parts of many estuaries. Typical losses on leased bottoms were: the James River, 10%; the York River, 2%; the Rappahannock River, 50%; and the Potomac River tributaries (Virginia) 70%. Economic loss was in excess of 7.9 million dollars. There was a nearly complete absence of oyster larvae attachment (setting) in 1972. Other effects of Agnes included a nearly complete loss of soft clams, Mya arenaria, in the Rappahannock River. Hard clams, Meraenaria meraenaria, were killed in the upper part of the York River. Oyster drills, Urosalpinx ainerea, were eliminated from the Rappahannock and reduced greatly in numbers in the York and James Rivers.https://scholarworks.wm.edu/vimsbooks/1074/thumbnail.jp

Hydrography and hydrodynamics of Virginia estuaries. XVII, Mathematical ecosystem modeling study of the York River

The York River drainage basin is rural, with an economy based on farming, logging, fishing and recreation. Water quality conditions are generally good, with low chlorophyll and nutrients and low fecal coliform counts. Dissolved oxygen concentrations are high except for periodic deoxygenation of the water deeper than 8 m in the reach extending 10 km upstream of the mouth. A quasi-three dimensional tidal average model was constructed and calibrated using intensive field data collected in June and July, 1976 and verified using slack water run data from September, 1976. The model components are: salinity, fecal coliform, chlorophyll, CBOD, dissolved oxygen, organic nitrogen, ammonia, nitrate plus nitrite, organic phosphorus and inorganic. phosphorus. Model runs revealed that the deep-water deoxygenation is a natural condition little influenced by human activity and that the York is insensitive to point source loadings, owing to its enormous volume