Fig 1.
Geographical map showing the 80 field sampling locations (red dots) in this study for oyster habitat suitability model development in the South-eastern coastal waters of Bangladesh.
Table 1.
Example of distinct environmental variation (mean ± standard deviation based on four observations during the monsoon period and three observations during the non-monsoon period) in monsoon and non-monsoon months (Location: Kutubdia channel;Year 2016).
DO = Dissolved oxygen; Chla = Chlorophyll a; PIM = Particulate inorganic matter.
Fig 2.
Tree diagram illustrating the relationships among environmental variables, life stages, and habitat types used to setup the Habitat Suitability Index (HSI) for the rock oyster S. cucullata.
Fig 3.
Relationships between environmental variables and associated habitat suitability values for the rock oyster S. cucullata.
Top two graphs (V1, V2) were used for larval settlement, while the other graphs (V3-V8) were used for the post-settlement period in the model (see Table 2 for sources).
Table 2.
Data sources used to generate suitability index graphs for oysters.
Fig 4.
Environmental variables (salinity, water flow velocity, temperature, pH, dissolved oxygen, PIM, and chlorophyll-a) showed both spatial and seasonal (monsoon vs no-monsoon period) variations along the investigated sites.
Sites are ordered from south to north (see Fig 1).
Fig 5.
Map summarizing the results of the HSI indicating the suitability of the investigated sites (coloured lines), and verification of the model results with observed oyster density (coloured circles).
Data not measured are sites (n = 27) where no substrate was available and therefore omitted from the oyster population survey.
Table 3.
Estimated length of the coast corresponding with HSI scores.
Fig 6.
Habitat suitability index (HSI) scores derived from seven environmental datasets correlated against: live oyster density (top left), shell height (top right), condition index (bottom) shown with standard deviation (n = 53). The 0.95 confidence bounds (grey coloured) were calculated with the bootstrap (quantile) method.
Fig 7.
Scatter plots and correlation coefficients (correlations > 0.7 are shown in bold) among the independent (Temperature, dissolved oxygen, pH, salinity, PIM, chlorophyll-a, water flow rate) and dependant variables (CI, shell height, oyster density).
Table 4.
Summary of linear regression models that were used to correlate among the dependant variables (oyster density, condition index and shell height) with independent environmental variables (for more details including the beta values of each predictors, see S2 Table).