conducted done from small, flat-bottomed 

 skiffs (bateaus). 



(3) The majority of the (clumped) 

 oysters collected today are of a quality 

 that makes them less suitable for the raw 

 bar trade than for canned oysters. Thus 

 the oyster industry in the study area 

 traditionally has been an oyster steam- 

 canning industry. 



(4) Of the intertidal oysters har- 

 vested, the most valuable, in terms of 

 their shape, size, and condition, are 

 found low in the intertidal zone rather 

 than in mature reefs, or oyster rocks, as 

 they are called locally. 



(5) Oyster production or total har- 

 vest apparently peaked in the early 1900's 

 and has steadily declined for numerous 

 reasons as follows: over-harvesting and 

 generally poor management; pollution, re- 

 sulting in closing many local areas to 

 oystering; labor problems, i.e., a dwin- 

 dling number of people willing to work in 

 the labor-intensive oyster industry; and 

 changes in the hydrology of local area. 



(6) Total oyster production from the 

 study area (principally South Carolina) 

 accounts for about 8% of total U. S. pro- 

 duction (Lee and Sanford 1963). Table 2 

 from Gracy et al. (1978) summarizes recent 

 oyster production from the study area and 

 includes both subtidal and intertidal oys- 

 ters. Presently it is unclear if the de- 

 cline in intertidal oyster harvest indi- 

 cates a decline in mature oyster reef den- 

 sity. For example, the closure of coastal 

 areas to oystering because of pollution by 

 human pathogens is in some respects bene- 

 ficial to natural oyster reef populations 

 that are thereby assured of nonexploita- 

 tion. On the other hand, hydrologic 

 changes accompanying marsh alteration and 

 increased coastal activities are likely to 

 be extremely damaging to the somewhat 

 fragile reefs. In Section 4.2 we discuss 

 the historical change in reef density in 

 the study area. 



In summary, the true mature oyster 

 reef subunit of the coastal ecosystem in 



the study area is not of commercial inter- 

 est because the reef oysters are of poor 

 market quality. The exception to this is 

 that high reef oysters can be removed and 

 replanted lower in the intertidal zone. 

 The increased efforts at oyster management 

 in the study area could benefit natural 

 reefs in that additional sources of oyster 

 larvae could be created. The commercial 

 exploitation of intertidal oysters ulti- 

 mately will depend on the study area's 

 economic climate. Increased mechanization 

 that would solve the labor problem (Hixson 

 1975) is constrained by continual rise in 

 energy costs. 



2.5 ENERGY SUMMARY 



A summary of estimates of energy flow 

 in oyster reefs in the study area appears 

 in Figure 12. These estimates were based 

 on the most reliable available information 

 (see the Appendix for details and ration- 

 ale). The numbers shown in Figure 12 are 

 the values for standing oyster biomass and 

 for oyster respiration rate. The respira- 

 tion estimate is particularly important as 

 an index of oyster function because it 

 represents the energy "tax" paid by reef 

 oysters to support their other activities. 

 The ratio between average biomass (kcal/ 

 m2) and respiration (kcal/m^/yr) gives the 

 turnover time of the oyster portion of the 

 reef as 0.38 yr (or 2.6 times/yr). This 

 is the average time that any given organic 

 carbon molecule "survives" as a constitu- 

 ent of oyster tissue before becoming oxi- 

 dized to CO2 and recycled. Gamete produc- 

 tion represents another high energy expen- 

 diture, and the typical watery tissue of 

 "coon" oysters in reefs is symptomatic of 

 oysters that are continually spawned out 



(or subjected to a po 



itinual ly 

 or diet). 



The extremely high ingestion and 

 egestion (biodeposition) estimates are ap- 

 proximate but indicate the qualitative im- 

 portance of reef oysters in the study area 

 for transferring suspended organic matter 

 to the reef surface. This process supports 

 the high bacterial metabolism noted in 

 Section 3.3, which in turn accelerates the 

 rate of carbon flux through the ecosystem. 



32 



