# Mediterranean Aquaponics: Fasting and Refeeding in a Polyculture Aquaponic System
## 4 Discussion
### Fish Growth Performance  
Previous studies [41; 42] examined a similar feeding pattern. According to [PERSON] et al. [42], when _Aciepenser dabryanus_ ([PERSON], 1869) was subjected for 28 days to zero, three, and seven days of fasting per week, followed by 14 days of refeeding, the final weights of fish subjected to zero or three days of fasting were similar. The same results reported by [PERSON] et al. [41] for _Tropheus_ sp. Over a study period of 80 weeks, fish were subjected to zero or four days of fasting per week for 20 weeks (followed by 60 weeks of refeeding); at the end of the study, the body size of the fish was similar. This feeding trial was based on the results of these studies [41; 42]. The results of the fish growth performance study indicated a significant impact of fasting on compensatory growth. The sea bass subjected to fasting treatments (B and C) demonstrated superior growth and total compensatory growth compared to the fish that were provided with daily nonurishment (A). It is crucial to consider the impact of refeeding on compensatory growth. In instances of complete compensation, starved fish ultimately attain the same size and age as their continuously fed counterparts [43; 44]. The findings of this study are at odds with those of [PERSON] [44] for _Gadus morhua_, where weight did not demonstrate a compensatory effect at the end of the three weeks of refeeding. In the present study, fish grown in a multi-culture aquaponic system and fed according to the treatment B protocol exhibited the highest weight gain (WG, g) and the highest specific growth rate (SGR, %/days) (ANOVA, \(p\) > 0.05). The survival rate of the fish at the conclusion of the experiment ranged from 93.3% to 84.5%, a figure that was significantly lower than the survival rates reported by [45] for _Acanthopagrus latus_ ([PERSON], 1782) (96.7-100%) and _Sparidentex hasta_ ([PERSON], 1948) (83-96%). The Fulton condition factor (K), which serves as an indicator of fish well-being, demonstrated no statistically significant differences between treatments (ANOVA, \(p\) > 0.05), indicating that short-term food deprivation does not exert a considerable impact on fish welfare. Subsequently, the Fulton condition factor value at the conclusion of the 75-day growing period was compared with values obtained from other studies. The value obtained in this study was found to be lower than the K value reported for Atlantic cod (K: 1.31 \(\pm\) 0.11 g/cm\({}^{3}\), 1.27 \(\pm\) 0.11 g/cm\({}^{3}\), and 1.22 \(\pm\) 0.11 g/cm\({}^{3}\)) when one-, two-, and three-week fasting periods were followed by a one-week refeeding program [44]. Ref. [45] reported higher K values (1.1 to 1.4 g/cm\({}^{3}\)) for _A. latus_ subjected to a two-week refeeding period. The Fulton Factor (K) serves as a verification method for the level of energy reserves and the health status of the fish. Fluctuations in its value may be indicative of alterations in the nutritional status of the fish [46]. It has been reported that fasting can induce oxidative stress in fish, which in turn results in a reduction in stored antioxidants and nutrients [47]. Protein degradation can be increased in order to provide amino acids for vital body functions [47]. Moreover, the findings indicated that sea bass cultivated in a brackish water aquaponic system and nourished in accordance with the feeding protocol of treatments B and C demonstrated a markedly elevated mean final weight in comparison to the values observed in treatment A (daily feeding). The findings of the present study are consistent with those of [48], where it was observed that gilthead seabream with an initial mean weight of 5.85 \(\pm\) 0.54 g reached a mean final weight of 27.08 \(\pm\) 0.8 g after eight days of feeding followed by two days of fasting. It was reported that the grey mullet exhibited a four times increment in mean final weight when starved for 5 and 20 days [48].