Modeling the filter-feeding behavior of the Pacific oyster (Crassostrea gigas) in response to natural variations in seston availability in Santa Catarina, Brazil

This study investigated the feeding behavior of the Pacific oyster ( Crassostrea gigas ) in response to natural variations in seston availability in Santa Catarina, Brazil, to inform assessments of ecological carrying capacity and sustainability certification. Field experiments were conducted at two sites using a flow-through biodeposition system to measure clearance, filtration, ingestion, rejection, and absorption rates under variable seston conditions. Organic and inorganic contents of feces and pseudofeces were quantified to estimate feeding efficiencies. A deterministic, nonlinear model was developed using STELLA software to simulate oyster feeding processes, integrating 18 equations and 26 variables driven by time series of total, organic, and inorganic particulate matter. Clearance and filtration rates decreased as seston concentration and organic content increased, showing a parabolic relationship. Net organic ingestion and absorption rates were highest at intermediate seston quality and quantity, with absorption efficiency declining at very low or high filtration rates. The model accurately reproduced observed trends and predicted annual biodeposit production of 74.15 tons of pseudofeces and 18.13 tons of feces for a typical 3-ha farm. A sensitivity analysis revealed feces production was the most responsive output to changes in seston properties. The model provides a robust framework for predicting the ecological effects of oyster aquaculture and can be applied to evaluate farm-scale impacts on water quality and sediment enrichment. This approach supports evidence-based certification and management of bivalve farming by quantifying biological processes and their environmental interactions under realistic field conditions.