Powell et al.: Multiple stable reference points in oyster populations 
135 
75 ° 30 ' 
75 ° 20 ' 
75 ° 10 ' 
39 ° 25 ' 
39 ° 20 
39 ° 
39 ° 10 ' 
39 “ 25 ’ 
39 ° 20 ' 
39 ° 15 ' 
39 ° 10 ' 
75 ° 20 ' 
75 ° 10 ' 
Figure 1 
The twenty natural oyster beds of the eastern oyster (Crassostrea virginica) in the New Jersey waters of 
Delaware Bay may be characterized in terms of high-quality (dark shade) and medium-quality (light shade) 
grids. The term “quality” refers to a relative differential in long-term average oyster abundance (Powell et al, 
2008). The footprints for the Middle bed (upper portion of figure) and the beds downbay from it, exceptNew 
Beds, Egg Island, and Ledge, were updated with data from surveys in 2005 and 2006. The footprints for the 
remaining beds were based on historical definitions. 
Throughout this contribution, we will refer to these bay 
regions where necessary, but in general, we will model 
the entire stock. In the following section, we summarize 
the biological relationships identified by Powell et al. 
(2009) without further discussion. 
Natural mortality fractions were obtained from box 
counts (be) under the assumption that 
^ oysterSf_i ~ ^ boxeSf + ^ live oysters t > HI 
where N = the number of individuals. 
Hence, 
= NboxeSt ( 2 ) 
bc N, + N, 
boxes f live oysters f 
where <P hc = the fraction of the individuals alive at the 
end of year t that died during the next year. 
