University of Guilan Caspian Journal of Environmental Sciences 1735-3033 24 1 2026 01 01 Optimum growth, enzymatic and biochemical reactions of stellate sturgeon, Acipenser stellatus juveniles in response to the feeding frequency and exposure to environmental salinity 239 251 7563 10.22124/cjes.2024.7563 EN Seyedeh Maryam Ahmadi Department of Fisheries, La.C., Islamic Azad University, Lahijan, Iran Habib Vahabzadeh Roudsari Department of Fisheries, La.C., Islamic Azad University, Lahijan, Iran Hossein Khara Department of Fisheries, La.C., Islamic Azad University, Lahijan, Iran Zabih Ollah Pajand International Sturgeon Research Institute of the Caspian Sea, Iranian Fisheries Sciences research, Agricultural Research, Education and Extension Organization (AREEO), Rasht, Iran Mohammad Sayad Borani Inland Waters Aquaculture Research Center, Iranian Fisheries Sciences research, Agricultural Research, Education and Extension Organization (AREEO), Bandar Anzali, Iran Journal Article 2024 02 15 The salinity and feeding frequency are two fundamental challenges in breeding stellate sturgeon, <em>Acipenser stellatus</em> juveniles both for aquaculture and restocking purposes. We evaluated growth indices, biochemical and digestive enzymes, osmoregulation indices, and gill tissues of 810 stellate sturgeons (10.96 ± 0.89 g in weight and 12.64±0.96 cm in length) in 9 treatments including three salinity levels with three types of feeding during eight weeks of rearing. The treatments included two, four and six times (2T, 4T and 6T) of feeding in combination with zero, 6 and 12 ppt salinities (0‰, 6‰ and 12‰). The main growth indices and food efficiency exhibited an upward trend by increasing in salinity and feeding frequency. The average final weight and length in 6T + 12‰ were higher than in other treatments. In addition, the highest average condition factor was measured in 4T + 6‰ (p < 0.05). The average food conversion ratio of all treatments decreased compared to 2T + 0‰. Alkaline phosphatase (ALP) in 2T + 0‰, alanine aminotransferase (ALT) in 6T + 6‰, 2T + 12‰, 4T + 12‰, 6T + 12‰, and aspartate aminotransferase (AST) in 4T+12‰ and 6T+12‰ were higher than in the other treatments (p < 0.05). The highest amount of amylase was measured in 2T + 6‰ and lipase in 6T + 0‰, 2T + 6‰, and 4T + 12‰ (p < 0.05). The results of the investigated indices showed that it is not necessary to increase meals at higher salinities. In addition, raising the salinity of the breeding environment to 6 ppt is favorable for safety factors and fish growth. https://cjes.guilan.ac.ir/article_7563_76c1a904083669b6586c3fbaa00338f0.pdf