Efforts to restore the native oyster in the Chesapeake Bay enjoy enormous public support and have consumed and continue to consume vast, some would argue unreasonable and unjustifiable, amounts of funding. Despite this support the stated goals of restoration efforts are poorly defined and consequently provide no realistic measures of success in terms of time, space, or biomass. Quantitative approaches used successfully in management of and rebuilding plans for other marine and estuarine species have not been appropriately applied. Basic information in oyster population dynamics and ecology has been inadequately appreciated in defining the quantitative problem. Given these limitations it is not surprising that little success has been achieved despite the massive investment. We note a lack of ability to predict recruitment, and limit the ingress and impact of disease. Without control of both of these functions, populations cannot be managed in a self-sustaining rebuilding mode within the footprint that they either currently occupy or formerly occupied. Sustained expansion of that footprint through substrate provision is prohibitively expensive, beyond the limits set by availability of substrate material, and futile in the presence of disease and susceptible oysters. Without attaining a substantially increased and rebuilding population, ecological services will be limited. Water quality impacts will, in reality, be modest, local and seasonal, and still subject to being overwhelmed by periodic storm events. Coherent and rational evaluation of biological limitations will lead to more realistic, and indeed very modest goals for ecological restoration. We must accept the fact that efforts to date to restore native oyster populations have failed and the prognosis for improvement of this situation is continued failure. The argument is proffered that stabilizing the present bed footprint with a realistic and sustainable population and the promotion of aquaculture to increase commercial yield is a more predictable and stable economic investment. Each of these options is consistent with the most realistic ecological outcome and should take priority in future efforts.

The eastern oyster, Crassostrea virginica (Gmelin, 1791) has been in decline along the eastern seaboard, and especially in Chesapeake Bay, for decades because of over-harvesting, disease and declines in water quality and suitable habitat. Eutrophication has also been increasing over the past half century, leading to increases in hypoxia and harmful algal blooms (HABs). The effects of two common Chesapeake Bay HAB dinoflagellates, Karlodinium veneficum, and Prorocetnrum minimum were tested on larvae of C. virginica and the Asian oyster being considered for introduction to Chesapeake Bay, C. ariakensis. When embryos from freshly spawned C. virginica and C. ariakensis were exposed immediately to K. veneficum at 10⁴ cells mL⁻¹, virtually all of the developed larvae were deformed within 48 h in one experimental trial, but not in a second trial in which algae were at a different growth stage. No deformities, and mortalities of <45%, were observed in controls to which a standard diet of the haptophyte Isochrysis was added. When 2-wk-old larvae of both species were exposed to the same HAB species, the effect was a severe reduction in motility with K. veneficum, but with P. minimum only C. ariakensis was affected and not C. virginica. Comparisons were made of the frequency of these HABs in Chesapeake Bay from long-term data analysis and the temporal period of spawning. Whereas both blooms are more common during the summer months, the frequency of blooms of K. veneficum and the period of oyster spawning, June to September, coincide more strongly. To compare spatial similarity, results of a larval transport model were compared with observational data for K. veneficum. This comparison demonstrated a significant overlap in July, particularly in the northern reaches of the Bay. These eutrophication-related HABs thus have the potential to reduce survival of early life history stages of oysters and hence to reduce oyster recruitment. Any reduction in recruitment either spatially or temporally, combined with an overall reduction in sheer numbers of larvae that survive, will make restoration or establishment of significant, self-sustaining populations of natural or introduced oyster species much more difficult.

Landings of eastern oysters (Crassostrea virginica) along the United States East Coast (mainly Rhode Island through South Carolina) increased to nearly 27 million bushels by 1890s, but they then declined by nearly 60% to 11.5 million bushels by 1940 and by almost 99% to 0.35 million bushels by 2004. Though overharvesting usually has been cited as the primary factor for the decline in landings from 1890 to 1940, the principal causes were: (1) a fall in demand for oysters, because consumers became aware that oysters could contain pathogens and competition from other foods increased in markets; (2) three economic depressions; and (3) biological and physical damage to the oysters and their beds (predation, siltation, severe storms, channel dredging, and harvesting by dredges). As a consequence of a huge decline in oyster landings in Delaware and Chesapeake Bays during and after the 1960s because of high oyster mortalities caused by the diseases MSX and Dermo, space became available in the United States national oyster market. The oyster industries of Prince Edward Island, Long Island Sound (Connecticut and New York), and the United States Gulf Coast took advantage of this and increased their production.

Recurrent larval and spat mortality (>80%) occurring in most Sydney rock oyster, Saccostrea glomerata, hatchery-runs since 1980 has prevented reliable commercial hatchery supply of spat and ultimately precluded the industry from accessing stock from breeding programs for faster growth and disease resistance. To overcome larval and spat mortality, the interactive effects of temperature and salinity on early life stages (embryos, larvae, and spat) of S. glomerata were investigated to optimize rearing conditions and thereby improve survival and growth. The early ontogenetic stages of S. glomerata were held at temperatures in the range from 16°C to 30°C and salinities in the range 10–35 ppt. Development of embryos to D-veliger larvae was significantly affected by temperature (P < 0.001), salinity (P < 0.001) and the interaction of these factors. Most rapid embryonic development occurred at a salinity and temperature of 35 ppt and 26°C. Growth of D-veliger, umbonate and pediveliger larvae was also significantly affected by salinity (P < 0.001) and temperature, as was the growth of spat. Salinity had a significant effect (P < 0.001) on D-veliger larvae and spat survival, whereas temperature had a significant effect (P < 0.001) on D-veliger and pediveliger survival. Survival and growth of umbonate larvae were not affected by either salinity or temperature within the range tested. Surface-response plots were also used to examine interactions between salinity and temperature. The optimal temperature for growth of D-veliger larvae was 28°C and for umbonate and pediveliger larvae was 30°C. Greatest length increases for D-veliger and umbonate larvae occurred at the maximum salinity level (34 ppt) whereas the salinity at which this occurred for pediveliger larvae was 26 ppt. Survival of larvae at these optima exceeded 95%. Best spat growth was at a salinity of 35 ppt and a temperature of 30°C. Spat survival at this salinity and temperature combination was 82%. Maximum spat survival was 93% and was measured at a temperature and salinity combination of 23°C and 30 ppt.

A tool in the form of a habitat suitability index model (HSI) for the eastern oyster, Crassostrea virginica, was adapted to evaluate and compare the effects of alternative restoration plans in southwest Florida. A component of a large forecasting model, this tool simulates system response by examining the impact of freshwater inputs into the system. The eastern oyster is a good indicator species for modeling because of its sedentary nature and its susceptibility to natural and artificial changes. In addition, oysters form a complex three-dimensional reef structure, which provides habitat and food for numerous species of fish and invertebrates. The model focuses on salinity, temperature, depth, substrate, and high flow frequency as the particular requirements to determine habitat suitability for the eastern oyster. A geographic information system (GIS) incorporates the oyster HSI model, which includes larval and adult components, to determine responses spatially and temporally to facilitate the decision making process. This paper evaluates four hydrologic and land use scenarios for the C-43 West Basin Reservoir Project. Model results indicate that the Preferred Flow scenario and the future conditions with the Comprehensive Everglades Restoration Plan have higher HSI values then either the existing conditions or the future without the Comprehensive Everglades Plan.

Oyster size and morphology affect individual oyster physiology, reproductive biology, and habitat production as well as population ecological services and availability for commercial harvest. Options for oyster restoration and fishery facilitation for eastern oyster (Crassostrea virginica) populations in the Chesapeake Bay include the use of disease resistant diploid eastern oysters (DEBY strain), triploid eastern oysters, and triploid Suminoe oysters (Crassostrea ariakensis) with the objective of providing a marketable product in a reasonable time frame. Shell height-at-age, growth in shell height in relation to environmental conditions, ontogenetic changes in morphology, and changes in biomass for groups of triploid Suminoe, triploid eastern, and diploid DEBY eastern oysters held at identical grow out conditions for the first two years of their lives were evaluated.

Triploid Suminoe oysters reached shell heights of 76 mm (market size in Virginia of 3 in) at 1.1 y with triploid eastern oysters and diploid DEBY oysters attaining the same size at 1.2 y and 1.5 y, respectively. Increases in shell height were positively correlated with water temperature and salinity with the largest increases in shell height typically occurring in warmer months. Holding density significantly affected ratios of shell height (SH) to shell width (SW) and SH to shell inflation (SI) for all three oyster populations. Oysters at lower densities showed a decrease in SH:SI ratio indicative of increased cupping as well as a reduction in SH:SW indicating a trend toward more discoid or rounded form. Tissue dry weight (g) and ash free dry tissue weight (g) increased nonlinearly with size within each population and were statistically different across the three populations examined. Triploid Suminoe oysters had higher tissue weights than either triploid or diploid DEBY eastern oysters