Growth performances of gilthead seabream (Sparus aurata) fed alternative diets for “circular” land-based IMTA production

Developing alternative and sustainable fish diets and alternative farming systems such as the SIMTAP (Self-sufficient Integrated Multi-Trophic AquaPonic) system, are possible strategies to improve aquaculture sustainability. In the present study, three consecutive trials were carried out on gilthead seabream (Sparus aurata), aiming to develop possible sustainable diets to be used within an Integrated MultiTrophic Aquaculture or SIMTAP systems (www.simtap.eu). The three tested diets consisted mainly of detritivores and/or filter-feeders organisms (on dry matter basis): M1) 50 % mussels (Mytilus platensis) and 50 % clams (Chamelea galina) used in the Experiment 1 (initial fish body weight 6.78 g); M2) 50 % mussels, 30 % clams (C. galina), and 20 % polychaetes (Nereis virens), used in the Experiment 2 (initial fish body weight 37.21 g); M3) 49 % mussels, 30 % clams (Paphia textile), 20 % polychaetes (N. virens), and 1 % of mineral premix, used in the Experiment 3 (initial fish body weight 249.17 g). In both Experiments 1 and 2, the groups fed the experimental diets showed lower growth performances than the groups fed the commercial feeds, notably for final body weight and specific growth rate. On the contrary, when the same mineral mix included in the commercial feed was added to the experimental diet (diet M3, Experiment 3), the fish fed the alternative diet (M3) showed better Body Weight gain (101.54 ± 2.016 vs 84.18 ± 2.478) and Specific Growth Rate (0.55 ± 0.009 vs 0.44 ± 0.014), among others. Moreover, in the Experiments 1 and 2 the groups fed the alternative diets showed a better viscerosomatic index, while in the Experiment 3 both viscerosomatic (5.76 ± 0.146 vs 6.37 ± 0.235) and hepatosomatic (1.94 ± 0.053 vs 2.37 ± 0.086) index were improved significantly. In conclusion, the experimental diets may improve the growth performances of gilthead seabream, when a proper mineral dietary integration is considered. Finally, new studies should be carried out for further optimize nutritional traits of the diets alternative to commercial feeds, and properly assess their sustainability.