INTRODUCTION
Aquaponics is a sustainable food production system that integrates aquaculture and hydroponics, enabling the simultaneous production of aquatic animals and plants while reducing environmental impact. However, limited information is available on the role of stocking density in marine aquaponic systems, particularly regarding its effects on shrimp performance and halophyte productivity. This study aimed to evaluate the effects of different stocking densities on survival, growth performance, product quality of whiteleg shrimp (Penaeus vannamei), and biomass production of Salicornia in a coupled aquaponic system.
METHODS
The experiment was conducted in a greenhouse aquaponic facility at the University of Padua using a completely randomized design with three stocking densities: low (LD: 65 shrimp/m2), medium (MD: 123 shrimp/m2), and high (HD: 182 shrimp/m2), each with three replicates. Shrimp were reared in recirculating aquaponic systems integrated with vertical Salicornia cultivation using nutrient film technique (NFT). The trial lasted 50 days. Water quality parameters (temperature, dissolved oxygen, pH, nitrogen compounds, turbidity, chlorophyll) were regularly monitored. Growth performance (final body weight, specific growth rate, feed conversion ratio, survival), shrimp quality traits (morphometrics, lesion incidence, texture, color, pH), and plant biomass were measured. Statistical analyses included general linear models, logistic regression, and survival analysis.
RESULTS & DISCUSSION
Water quality remained within optimal ranges across all treatments. Turbidity (P = 0.049) and chlorophyll (P = 0.011) increased with stocking density, indicating higher suspended solids and phytoplankton biomass at higher densities. Survival averaged 85% and was not affected by treatment. Growth performance differed significantly (P < 0.001), with shrimp at low density reaching the highest body weight (~13–14 g) compared to medium (~10 g) and high density (~8 g). Conversely, total biomass increased with density (P = 0.010), reaching 559.6 g (LD), 783.4 g (MD), and 930.7 g (HD), with biomass growth also higher in MD and HD (P = 0.014). Feed conversion ratio was unaffected (P = 0.823). Lesion incidence did not differ among treatments but increased with body weight (P < 0.001). Shrimp at low density showed higher carcass weight and body size (P < 0.001), while most meat quality traits were unchanged; however, cooked redness (a*) was higher at lower densities (P = 0.011). Salicornia yield increased with stocking density, reaching 12.05, 10.49, and 9.87 kg m-2 in HD, MD, and LD, respectively.
Overall, a clear trade-off emerged: lower densities improved shrimp growth and quality, whereas higher densities maximized total biomass and plant production