Leila Abdoli

Citrus ( Citrus limon ) by‐products, particularly lemon peel, are rich in bioactive compounds with known antioxidant and anti‐inflammatory properties. This study evaluated the effects of lemon peel extract (LPE) supplementation on growth performance, immune responses, and antioxidant activity in Pacific white shrimp ( Litopenaeus vannamei ). Over a 60‐day period, shrimp were fed four diets: a control diet (0%) and three diets with varying levels of LPE (0.5%, 1%, and 2%). The results showed that shrimp fed the 1% LPE diet exhibited significantly higher weight gain (WG), specific growth rate (SGR), and lower feed conversion ratio (FCR) compared to the control group ( p < 0.05). Additionally, shrimp fed 0.5% and 1% LPE showed significantly enhanced activities of antioxidant enzymes (catalase [CAT], glutathione peroxidase [GPX], superoxide dismutase [SOD]), lysozyme, total protein, and hemocyte counts, including large granular cells (GCs), semi‐granulocytes, and hyaline cells (HCs) ( p < 0.05). Total hemocyte counts (THCs) were also significantly higher in all LPE‐treated groups compared to the control ( p < 0.05). Plasma glucose levels were reduced in the 0.5% and 1% LPE treatments, though the decrease in cholesterol was not statistically significant. Moreover, the expression of integrin β , PX , and α2-M mRNA was significantly upregulated in shrimp fed the 2% LPE diet, while LGBP and proPO1 mRNA expression were higher across all LPE treatments. In conclusion, dietary supplementation with LPE, particularly at 0.5% and 1%, enhances growth performance, immune response, and antioxidant activity in L. vannamei . Therefore, LPE presents a promising and cost‐effective feed additive for shrimp aquaculture, with the potential to enhance disease resistance, support immune function, and ultimately improve shrimp health and productivity under farming conditions.

The stomach contents of Pomadasys stridens were studied monthly in the Persian Gulf (Hormozgan province) from October 2020 to October 2021. The stomach contents analysis of 591 fish included a wide variety of food items such as bony fish, crustaceans, molluscs, echinoderms, plant materials, annelid worms, and miscellaneous materials. Although the food component percentage differed marginally between sexes, it was not statistically significant (P=0.19). The vacuity index revealed that P. stridens is a gluttonous species (19.5 %) and the amount of this index was not significantly different in both sexes, length classes, or months. The food preference varied by size: in younger fish, the dominant food item was fish prey, followed by unknown materials, crustaceans, and plant material, and in larger fish (often including sex-determined fish), the food preference shifted to mostly molluscs, crustaceans, and mixed food groups. These preferences also differed significantly across sexes and months (P<0.05). The Penaeid shrimps made up a major portion of P. stridens` diet. Therefore, any change in the stocks of each prey and their predators can have a significant effect on their exploitation potential in the region.