Powell et al.: Multiple stable reference points in oyster populations: Crassostrea virgimca in Delaware Bay 
127 
Figure 17 
The broodstock-mortality relationship for the eastern oyster ( Crassostrea virginica ), 
1953-2006, time period for the natural oyster beds of Delaware Bay, showing low-abun- 
dance consolidated years (1960-1963 and 1996-2006), high-abundance consolidated 
years (1971-1978), high-abundance dispersed years (1979-1984), and low-abundance 
dispersed years (1987-1995). The solid line is the curve fitted from Equation 6. The 
dotted lines represent the 54-yr medians which define the four quadrants (Fig. 10). 
Consolidated and dispersed refer to the proportion of the population on medium-mortality 
beds (Fig. 5) above or below the 54-yr median, respectively. The upper graph presents 
the entire dataset and the lower graph focuses on years of abundance <5 x 10 9 . 
abundance regime is noteworthy for low mortality 
and high recruitment, regardless of stock disper- 
sion. However, during low-abundance intervals, the 
consolidated stock is in a relatively stable state and 
characterized by low mortality and low recruitment. 
The dispersed state is moderately less stable, char- 
acterized by higher mortality and higher recruit- 
ment. The interesting coincidence of similar trends 
in mortality and recruitment in both instances is 
noteworthy. 
