الفهرس 
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Abstract
Aquaculture is one of the most rapidly expanding food-producing sectors. However, the threat of plastic pollution in the environment is currently gaining international attention. Furthermore, contamination of aquatic ecosystems by bulk plastics and plastic debris is currently one of the most serious global problems. So, this study was carried out to clarify the ecotoxicological effects of microplastic pollution coupled with applying feed restriction strategies on the freshwater aquatic environment under biofloc system conditions” growth performance, health assessment indices, water quality, zooplankton community, feeding and ventilatory behaviour, stress related genes and neurobehaviour” of common carp (Cyprinus Carpio). A total 180 fish with an average weight of 36.3 g ± 0.15 g were stocked at nine 1000 L fiberglass tanks (Each tank was filled with 400L (40 L matured biofloc and 360 L of well water)) (20 fish each) and installed inside a polycarbonate greenhouse. All tanks were exposed to microplastics for 5 months with an average concentration of 15.9 mg/L per tank with three different feed restriction strategies (each with triplicates) were set as follows: the first treatment (T1); feed was provided 4 days a week and 3 days fasting; the second treatment (T2); feed provided 3 days a week and 4 days fasting; and the control group; feed was supplied 6 days a week and 1-day fasting. The obtained results indicated that microplastics with feed restrictions significantly (P≤0.05) impaired the growth performance parameters (average body weight and weight gain) in all treatments in particular in the feed-restricted groups. Also, the feed-restricted groups showed a decrease in the sensitivity toward the added feed and increased feeding time, it indicated that microplastics significantly (P≤0.05) hindered the feeding activity, especially under fasting conditions. In addition, our study showed that the microplastic significantly(P≤0.05) increased the deformity percent of zooplankton and markedly decreased in its count in feed-restricted groups, especially T2 when compared to their control counterparts. Furthermore, microplastic particles accumulated in the vital organs like gills, intestine, liver, and brain causing remarkable pathological alterations, particularly in feed-restricted groups. Malondialdehyde (MDA) and hydrogen peroxide (H2O2) levels were significantly (P≤0.05) increased in feed-restricted groups, especially in T2, while total antioxidant capacity (TAC) was significantly (P≤0.05) decreased in feed-restricted groups. Over the experimental period a sort of microplastic degradation occurred that lead a reduction of the particles size due to biological degradation where the smallest particles were in T2 group while the largest were in the control group. Finally, microplastic pollution with feed limitations made remarkable neurobehaviour alterations represented by changes in locomotor activity, aggression, exploratory nature, and predator avoidance behavior in all groups and significantly (P≤0.05) upregulated the m-RNA levels of TNFα, Hsp70, Cas-3, Cyp1a, and Mt1 genes. In conclusion, the obtained results refer to the role of lengthening the fasting period in aggravating the impacts of microplastic pollution on fish and under biofloc system conditions.