Fig 1.
Modular reef was deployed subtidally in 7 m depth at Steamer Rock in the Rappahannock River, Virginia in October 2000 and sampled in late May 2005.
Fig 2.
Schematic design of a single module.
Total surface area of each module was 74.17 m2, with 3.11 m2 each on the Top and Bottom faces, 2.89 m2 on the Side faces, and 5.73 m2 on the Hole faces. Five modules were stacked to comprise one modular reef. Schematic was based on dimensions provided by Retired Naval Captain Robert Jensen (deceased) and McLean Construction Company.
Fig 3.
Top three modules of the modular reef that were sampled and immediately returned to the same location.
Individuals in the photo are, from left to right, Captain R. Jensen, R. Lipcius, and K. Knick. Photo by L. Latane.
Table 1.
Characteristics of the five potential cohort structures for eastern oyster examined with the R package mixtools.
There were four year classes with either one or two cohorts, except in 2003 when spatfall and oyster abundance were too low to distinguish more than one cohort. Nominal = starting values entered into mixtools for mean size of each cohort; μ, σ and proportion = estimates of cohort mean size, standard deviation, and proportion of the population in each cohort generated by mixtools.
Fig 4.
Visible are oyster clusters, hooked mussels and redbeard sponges Clathria prolifera, which are characteristic of a healthy subtidal oyster reef. Inset: closeup of a large, live eastern oyster of approximately 130 mm shell height.
Table 2.
Results of the AIC analysis for live oyster density, mussel density, and oyster biomass m-2.
In all three cases, the best-fitting model provided a significantly better fit than all other models (Log-likelihood X2 test, p < 0.0001).
Fig 5.
Live oyster density and mussel density.
Density m-2 by face of the modular reef.
Table 3.
Live oyster and mussel density standardized to (i) surface area of each face (density m-2 surface area, (ii) density m-2 river bottom on each module, which is a product of the density m-2 surface area and total surface area per face on a module, and (iii) density m-2 river bottom on the five-module modular reef.
Total surface area of each module was 14.84 m2, with 3.11 m2 each on the Top and Bottom faces, 2.89 m2 on the Side faces, and 5.73 m2 on the Hole faces.
Table 4.
Live oyster density, standardized to density m-2 river bottom on the five-module modular reef, for the typical categories in oyster fisheries.
Fig 6.
Relationship between live mussel density and oyster density.
The curve is sigmoid and statistically significant (Nonlinear least squares regression, SigmaPlot 13, p < 0.0001).
Table 5.
Results of the AIC analysis for size structure of live oysters using the only two realistic models, both with four year classes, and one with five and the other with six cohorts.
The best-fitting model with six cohorts provided a significantly better fit (Log-likelihood X2 test, p < 0.0001).
Fig 7.
Size frequency of live (a) and dead (b) oysters on the modular reef.
The cohorts were distinguished using the R package mixtools. Cohort parameters are in Table 1.
Fig 8.
Size frequency of live (a) and dead (b) mussels on the modular reef.
Fig 9.
Live oyster DM as a function of SH.
Fig 10.
Live oyster biomass, as dry mass (DM), by face of the modular reef.
Table 6.
Oyster biomass, as dry mass (DM), by module-face stratum combination.