Oyster Density & Biomass

Oyster density (number m-2) was estimated for each oyster reef by averaging the number of oysters collected from all samples on a reef within a year. These data are available back to 1993.

Biomass (DW, g dry tissue weight): Data from a size range (30-139 mm shell length) of live oysters (n= 73) collected from Swash in the James River  (JR, Reef 13, Figure 1 in Mann et al. 2009) in November 2004 (n = 24), 2005 (n = 24) and 2006 (n= 25) were used to estimate the relationship between oyster shell length (SL, mm) and biomass or dry tissue weight (g).  After the oysters were measured to the nearest mm, the tissue was removed and dried to constant weight (DW, g) at 80°C (72 hrs).  The resulting relationship is: 

  • Biomass (DW, g)  = 7.12 * 10-5 * Shell length (SL, mm) 2.15; (JR)

Additionally shell length to biomass relationships were developed for the Great Wicomico (GWR) and Piankatank River (PR) oyster populations. These were as follows:

  • Biomass (DW, g)  = 9.63 * 10-6 * Shell length (SL, mm) 2.743 (GWR)
  • Biomass (DW, g)  = 4.92 * 10-5 * Shell length (SL, mm) 2.299 (PR)

Biomass calculations were made for each size class (YOY, small at <75mm SL, and market at SL >75 mm), for each 5mm size class, and for each age class (see below) across all data as required (see later discussion in stock versus recruit relationship). The biomass values were estimated for each reef and river system/area as required.

Link to Age Structure