Shell Volume

Shell volume (L m-2) has been collected since 1998 coincident with the measurement of all boxes (articulated valves of dead oysters).  Since 2002 (since 2000 on a subset of reefs) shell has additionally been categorized as brown shell that has been exposed to oxic water above the sediment water interface, and black shell that was exhumed during the collection process. 

Wet shell weights (WSW, g) were collected from the same 73 oysters used in biomass determinations in the James River after the tissue had been removed and before the shells had air-dried.  The relationship between SL and WSW is described in Mann et al (2009) as follows:

Wet shell weight (WSW, g) = 0.002374 * Shell length (SL, mm) 2.21; R2 = 0.64, n = 73

This relationship was used to estimate the amount of live shell (g) observed in each patent tong on the basis of the available live oyster and demographics. Note that the exponents in equations describing (a) biomass versus SL and  (b) wet shell weight versus SL are remarkably close, indicating that a traditional meat weight: shell weight condition index (e.g., Walne and Mann, 1975; Mann, 1978) is approximately constant with size.

Wet shell volumetric conversion: a volumetric conversion was also estimated by weighing 1 L shell samples, including a range of shell types from whole shells to shell hash, collected from 5 reefs in the James River in November 2006. 

1 L of wet James River shell = 587.3 g +/- 22.6 g

Biomass to shell volume conversion: Combining the above relationships allows estimation of shell volume of live oysters from biomass using the relationship:

Volume (L) = 7.66 * 10-2 * biomass (DW, g) – 0.0014

This final relationship allows comparison of live animals associated shell to oxic brown shell at any chosen location. 

Link to Section 4 - Population Estimates