Stratified-random sampling methods were employed to collect data on oyster abundance, survival and growth on the reef structures. Little published work existed at the onset of this project detailing monitoring protocols for Oyster Castles®, thus methods were adjusted to obtain more accurate data as the project progressed. Despite these adaptations, similar metrics were collected throughout 2016-2022 using a stratified random sampling design. Moody et al. 2020b demonstrated that the less labor-intensive random sampling method generated shellfish densities and total abundance estimates similar to counting all shellfish on the structure. Monitoring was conducted in November-December of each year.

2016: Four calibrated transect lines were placed perpendicularly over each structure at randomly chosen locations. Three 10x10 cm flexible quadrats, made of nylon seatbelt material, were placed at random locations along each transect line. The location (interior or exterior) and orientation relative to the shoreline were recorded for each quadrat location. All live and dead oysters (still retaining articulated valves) within each quadrat (12 per structure) were enumerated and the shell heights of five oysters were measured. If there were not five animals present in the quadrat, the next closest five to the quadrat were selected. Percent coverage of ribbed mussels and other sessile, encrusting organisms was evaluated.

2017: An augmentation was made to the sampling method that stratified the samples by deck (course of block) to reduce bias from differences in density among strata and ensure that an equal number of quadrats were assessed from each deck. In total, 3 quadrats were counted per deck. Shell bag reefs were treated as having two decks: (1) the base and (2) top/crest. Additionally, only a subset of reef structures were sampled

2018-2022: An augmentation was made to use 25 x 25 cm flexible quadrats to accommodate larger oysters. At each selected sampling point, the nylon quadrat was positioned so that the opening allowed for viewing of the side and associated internal area of the block along the changing contour of the structure. Shellfish attached to the interior and exterior of the blocks were not examined separately.