Management and rebuilding of finfish resources, a field where we have enjoyed reasonable success, is based on a simple principle that recruitment will support population expansion at a rate in excess of population loss to the combination of natural mortality and fishing mortality. Thus R > (M+F) where R is recruitment, M is natural mortality and F is fishing mortality. Indeed this simple relationship is the basis of US federal sustainable fisheries management under the Magnuson Stevens Fishery Conservation and Management Act. This approach is, however, inadequate to ensure rebuilding and stability of oyster populations because any such effort must ensure rebuilding of BOTH the live oysters and the shell habitat component of the oyster reef complex. Stated simply, if the shell structure of a reef degenerates and disappears then any restorative action focused solely on live oysters will fail. A successful restoration and stable resource program must meet the guidelines of both R > (M+F) for live oysters and Sm > (Sd + Sb + Sf) where Sm is the addition of shell to the reef structure resulting from natural mortality, Sd is the loss of that shell to degradation associated with physical breakdown by biology (borers and surface microbiology) and dissolution (shell gradually dissolves), Sb is the loss of shell to burial (it thus becomes unavailable as a settlement substrate for additional generations of oysters even though it may stabilize the foundation of the reef), and Sf is the loss of shell to fishing, wherein it is removed from the system as either shell of live product or cultch where seed oysters are harvested for relocation. Thus oyster management is dictated not just by reference points for live oysters, but also for shell substrate – the dual reference point approach. The history of failure of many, indeed most prior restoration efforts and fisheries has been due to the lack of attention to the reference points for shell management. It is notable that even the restoration reference point developed by an expert panel for use in monitoring progress towards the “twenty estuaries by 2025” goal expressed in the Presidential Executive Order 13508 – Strategy for Protecting and restoring the Chesapeake Bay watershed (2011) lacks a quantitative reference to shell budgets.
