https://janb.guilan.ac.ir/ Aquatic Animals Nutrition en daily 1 Sun, 09 Aug 2026 00:00:00 +0330 Sun, 09 Aug 2026 00:00:00 +0330 https://janb.guilan.ac.ir/article_9757.html Introduction: The ability of fish to digest food particles depends on the presence of digestive enzymes in the gastrointestinal tract. In gastric fish species, proteolytic enzymes especially pepsin, trypsin, and chymotrypsin appear to play a very important role in catalyzing hydrolysis process of certain peptide bonds. Trypsin, as a serineprotease, complete the acid predigestion of protein delivered to the stomach in combination with other alkaline proteases and peptidases where specifically cleaves at the carboxylic side of lysine and arginine residues. Therefore, trypsin activity could be a sensitive and reliable indicator of nutritional and physiological status of fish at different stages of growth. The aim of this work was to study the effect of some physicochemical factors on the activity of extracted trypsin from pyloric caeca and intestine of Siberian sturgeon (Acipenser baerii).Materials and Methods: The collected fish viscera from 10 samples (5 ± 0.4 kg) were transported to the laboratory and after separating the pyloric caeca and intestine, those samples were washed with cold distilled water (4 °C), pooled and then homogenized in 50 mM Tris-HCl buffer. After centrifugation at 4 °C, the resulting supernatant from each sample was collected and finally, the physicochemical factors including optimum temperature, thermostability, optimum pH, pH stability, inhibitors and metal ions were evaluated on the extracted trypsin according to the standard protocols. Data obtained from the experimental assessments was analyses by a One-Way ANOVA and the comparison of means was carried out by Duncan’s multiple range tests with a statistical significance at P<0.05.Results and Discussion: According to the results, optimum temperature of the trypsin from pyloric caeca and intestine was recorded at 55 °C. Similar optimum temperature was recorded for trypsins in silver mojarra, unicorn leatherjacket, beluga and sevruga. The optimal temperature of trypsin is in the range of 30-60 °C and the differences could be attributed to the temperature of fish habitat or experimental conditions used in assessments. The stability of the trypsin was well preserved at temperatures of up to 50 °C. The results of thermostability were in accordance with those of mandarin fish, mrigal carp, common dolphin fish, beluga and sevruga. In general, thermostability of the trypsin enzyme might vary by some factors such as fish species and experimental conditions. The optimum pH of trypsin from both samples was recorded at 8.0 and the results were similar to data reported from trypsin in other species such as mrigal carp and common dolphinfish. The pH stability of trypsin from both samples was highly preserved at pH values comprised between 7.0 and 11.0. Similar results were reported for trypsins from grey triggerfish, zebra blenny, catfish, common dolphin fish, beluga and sevruga. The high ranges of pH may change the net charge and conformation of an enzyme and inhibit to bind to substrate properly, resulting in the abrupt loss of enzymatic activity. Trypsins are mainly known to be more activity within a range of pH values comprised between 7.5 and 10.5. The inhibitors SBTI, TLCK, PMSF, TPCK, pepstatin A, iodoacetic acid, and EDTA significantly inhibited the enzyme activity, whereas SBTI and TLCK had a completely inhibitory effect on the enzymatic activity (P<0.05). The sensitivity of protease enzymes to various inhibitors is a valuable tool for their proper functional characterization. Our findings were in agreement with data reported in the brownstripe red snapper, silver mojarra, zebra blenny, mrigral carp, Asian seabass, beluga and sevruga. The enzyme activity was significantly increased in the presence of Ca+2 and Mg+2 and decreased by Cu+2, Ba+2, Zn+2, and Al+3 (P<0.05). Our results were in agreement with data reported in mandarin fish, zebra blenny, common dolphin fish, beluga and sevruga. Metal ions can affect enzyme-catalyzed reactions by changing the electron flow in a substrate or enzyme and play a key role in binding to the substrate, depending on the functional groups present in the active site of enzyme.Conclusion: Based on the obtained results, the extracted trypsin activity from Siberian sturgeon pyloric caeca and intestine was significantly affected by the evaluated physicochemical factors that can be effective on the optimal activity of the enzyme in the digestive physiology of the fish. https://janb.guilan.ac.ir/article_9755.html Introduction: Algae are rich in bioactive compounds and can grow in harsh environments, producing secondary metabolites with high biological value. They are considered natural sources of antioxidants, offering safer alternatives to synthetic compounds like Butylated hydroxyanisole (BHA) and Butylated hydroxytoluene (BHT). Brown algae generally exhibit higher antioxidant activity than green or red algae. Green algae, such as the genus Ulva, are rich in proteins, minerals, fatty acids, and antimicrobial compounds. Materials and Methods: Microalgae (Tetraselmis tetrathele and Scenedesmus quadricauda) and macroalgae (Sargassum ilicifolium and Ulva lactuca) were collected, cleaned, dried, and powdered. Ethanolic and acetone extracts were prepared using maceration. Antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH), Ferric Reducing Ability of Plasma (FRAP), and 3-ethylbenzothiazoline-6-sulfonate)2/2- azinobis (ABTS) assays. All experiments were performed in triplicate, and data were analyzed using t-tests in SPSS. Results: Antioxidant activity varied significantly with algae species, solvent, and assay type. For macroalgae, S. ilicifolium showed higher antioxidant activity than U. lactuca, with acetone extracts more effective in DPPH, while ethanol extracts were stronger in ABTS. For microalgae, ethanol extracts of T. tetrathele and S. quadricauda showed higher DPPH and FRAP activity, while ABTS results showed high antioxidant capacity for both solvents. Solvent type influenced the extraction of different antioxidant compounds. Discussion: The results confirm that antioxidant capacity depends on species, extraction solvent, and assay method. Brown algae like S. ilicifolium contain diverse phlorotannins, enhancing free radical scavenging. Microalgae contain polar compounds like carotenoids and chlorophylls, which are better extracted with ethanol. Differences among assays reflect distinct mechanisms of antioxidant action. Conclusion: All algae studied are valuable natural sources of antioxidants. S. ilicifolium and T. tetrathele are particularly potent, highlighting the importance of species selection and extraction methods. Algae can be sustainably used in food, pharmaceutical, cosmetic, and biotechnological applications. https://janb.guilan.ac.ir/article_9754.html Introduction: Ornamental fish are aquatic animals primarily reared in aquariums and decorative ponds for aesthetic purposes rather than human consumption. Among freshwater ornamental species, koi carp (Cyprinus carpio var. koi) is one of the most popular due to its remarkable diversity of colors and patterns, which significantly determine its market value. Therefore, understanding pigments and their dietary sources is essential in ornamental aquaculture. Carotenoids are the main compounds responsible for coloration in ornamental fish, however, fish species such as koi cannot synthesize them independently and must obtain them through feed. Astaxanthin, an important carotenoid with strong antioxidant properties, supports health, immunity, and skin coloration. Lysophospholipids may enhance fat-soluble compound absorption, improving astaxanthin uptake. This study evaluated their effects on pigment absorption, immunity, and antioxidant indices in koi carp. Materials and Methods: A total of 150 koi carp (with an initial mean weight 3.63 ± 0.05 g) were purchased from a local farm and transferred to a private rearing facility. After a two-week acclimation period on a commercial ornamental fish diet, the fish were randomly distributed into 15 glass aquaria (60 L; 60 × 45 × 20 cm) with 5 treatments, 3 replicates, and 10 fish per aquarium. Water quality was maintained by filtration, at temperature 26 ± 1°C, pH 7.5 ± 0.5, and dissolved oxygen 7 ± 0.5 mg/L. Synthetic astaxanthin (>98% purity) and lecithin-based lysophospholipid were added to the basal diet by spraying with canola oil. Treatments included: control, 0.01% astaxanthin, 0.02% astaxanthin, 0.01% astaxanthin + 0.1% lysophospholipid, and 0.02% astaxanthin + 0.1% lysophospholipid. Fish were fed at 5% body weight, three times daily, for 56 days. At the end of the feeding trial, serum lysozyme, alternative complement activity (ACH50), immunoglobulin, and antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were measured using standard spectrophotometric methods. Serum, skin, and fillet carotenoids were also assessed. Data were analyzed using One-Way ANOVA followed by Duncan’s test in SPSS version 19, with significance set at P<0.05. Results: According to the immune parameters, lysozyme activity was significantly lower in the control and diet containing 0.01% astaxanthin compared to other groups (P<0.05). Immunoglobulin and complement activities were also significantly influenced by the different diets, with the combined astaxanthin–lysophospholipid groups showing the highest values (P<0.05). The highest CAT activity was recorded in fish fed the diet containing 0.01% astaxanthin supplemented with 0.1% lysophospholipid (P<0.05). The lowest SOD activity was observed in the control and 0.01% astaxanthin groups, while the addition of lysophospholipid to diets containing astaxanthin significantly increased SOD activity (P<0.05). Likewise, fish receiving the combination of lysophospholipid and astaxanthin, as well as the diet containing 0.02% astaxanthin, showed higher GPx activity than the control group (P<0.05). Carotenoid accumulation in the skin and fillet was significantly higher in fish fed astaxanthin-supplemented diets, particularly when combined to lysophospholipid (P<0.05). Discussion: Assessment of immune parameters in fish is an important indicator of health and immune efficiency, since these markers reflect both innate and acquired defense capacity. In the present study, adding astaxanthin to lysophospholipid synergistically improved lysozyme, complement, and immunoglobulin activities. This effect was probably due to better astaxanthin absorption caused by lysophospholipid, which enhances bioavailability through mixed micelle formation and facilitation of lipid transport. Antioxidant enzymes such as SOD, CAT, and GPx play crucial roles in mitigating oxidative stress and maintaining fish health. Here, astaxanthin-containing diets increased antioxidant enzyme activities compared to the control, and the best antioxidant performance was observed with combination of 0.01% astaxanthin and 0.1% lysophospholipid. This suggests a synergistic effect between the two additives. Similar improvements in antioxidant capacity have been reported in trout, tilapia, shrimp, and other aquatic species. Astaxanthin also increased carotenoid deposition in koi skin and fillet, improving pigmentation and likely market value. The inclusion of lysophospholipid further enhanced carotenoid accumulation in tissues, probably by improving emulsification and intestinal uptake of this fat-soluble pigment. In contrast, lower serum carotenoid levels in combined treatments may indicate faster transfer from blood to target tissues. Conclusion: Based on the present research, it can be stated that the combination of lysophospholipid and astaxanthin, particularly at the 0.01% level, likely enhanced tissue deposition of astaxanthin, which may reflect improved bioavailability, and concurrently improved antioxidant capacity and immune function. https://janb.guilan.ac.ir/article_9756.html Introduction:Saccharomyces cerevisiae fermentation product is a new fermented product. This product comprise rich source of nutrients that can possibly enhance immunity and growth fish.Materials and methods: In this experiment, the effects of various level of Saccharomyces cerevisiae fermentation product on the growth performance, survival and some Haemato-immunological responses in juvenile Asian seabass (Lates calcarifer) were investigated. The first, 240 healthy fish with an average body weight of 9/08±0/41g were randomly were distributed to 12 polyethylene tanks with a capacity of 300 L and density of 20 fish per tank. The fish were divided into four experimental groups in three replications and were fed with four diets as follows; control (without adding Saccharomyces cerevisiae fermentation product), FP1:0/5%, FP2:1% and FP3:2% Saccharomyces cerevisiae fermentation product. The fish were fed three times a day until satiation for 8 weeks. Growth performance and Haemato-immunological indices were conducted at end experimentResults and Discussion:The results indicated that adding Saccharomyces cerevisiae fermentation product in the diet significantly enhanced the Growth performance juvenile Asian seabass (Lates calcarifer). %WG, PER, SGR in FP1, FP2 and FP3 were significantly higher than control. In contrast, the lowest FCR values of 1,1/05,1/09 were recorded in FP3, FP2and FP1, respectively, indicating a positive effect of these Saccharomyces cerevisiae fermentation product on improving FCR. The present results showed that Hematological indices had no significant differences than the control group (p>0.05). However, The number of neutrophil in the treatments FP3 did show significant differences compared to the control group (P<0.05). Immunological assessments demonstrated significant increases in lysozyme activity, total protein, immunoglobulin levels, and albumin in serum Lates calcarifer fed with Saccharomyces cerevisiae fermentation product (P<0.05).Conclusion: The findings of this study suggest that using 1-2% Saccharomyces cerevisiae fermentation product in diets could improve the growth and immunity of juvenile Asian seabass (Lates calcarifer) https://janb.guilan.ac.ir/article_9811.html Biological information on commercially important fishes remains limited in many parts of the northern Persian Gulf despite increasing fishing effort in recent years. This study examined the length-weight relationship, condition factor, and length-frequency distribution of Longnose Trevally, Platycaranx chrysophrys, collected from the Basaidu area, northwest of Qeshm Island, Iran. A total of 42 individuals were sampled in December 2025. Total length was measured to the nearest 1 mm and body weight to the nearest 0.01 g. Length-weight relationship parameters were estimated using log-transformed linear regression, and Fulton’s condition factor was calculated for each specimen. The mean total length and weight were 37.60 cm and 613.10 g, respectively, and the mean condition factor was 1.19. The length-weight relationship was estimated as W = 0.2622L^2.13 (R² = 0.81), indicating negative allometric growth. Most individuals were concentrated in the 34-36 cm length class, and the observed size range was smaller than that reported in several previous studies from the region. These findings provide preliminary evidence of size truncation in the exploited stock and may reflect the effects of fishing pressure; however, broader seasonal and spatial sampling is required for robust assessment. https://janb.guilan.ac.ir/article_9826.html The proliferation of various pollutants, including heavy metals, has negatively affected numerous marine and freshwater ecosystems and their inhabitants. Heavy metals are non-degradable pollutants, and their measurement in water, sediments, and fish serves as an indicator of environmental contamination and its impact on human communities. The bioaccumulation of heavy metals across the food chain poses significant threat to human society. Considering the crucial role of fish muscle tissue in human nutrition, ensuring its safety is of particular importance.In this study, 24 wild common carp (Cyprinus carpio) weighing 1450±161g were randomly collected in April 2022 from fish markets in the cities of Astara, Hashtpar, Anzali, Rasht, Kelachai, and Kiashahr in Guilan Province. They were examined for the levels of four heavy metals: lead, zinc, cadmium, and mercury. Measurements were performed using an atomic absorption spectrophotometer.Following biometric measurements and coding, 100 g of muscle tissue was stored at −20 °C until digestion. The results showed no significant differences in the accumulation of heavy metals between male and female fish, nor between the heavy metal levels and the measured biometric traits of the experimental samples. The mean concentrations of zinc (24.73±14.24 µg/g dry weight), cadmium (0.003±0.00020 µg/g), lead (0.0252±0.001 µg/g) and mercury (0.0842±0.0659 µg/g) were found to be well within the permissible limits of international standards (FAO/WHO) and the Iran national standard (Iran Veterinary Organization). Since common carp larger than 18 mm are predominantly benthic feeders, sediment contamination can lead to pollution of small benthic organisms and subsequently transfer contamination to benthic and bottom-feeding fish. The lower levels of zinc, cadmium, lead, and mercury contamination observed in this study may indicate low contamination in sediments and small benthic organisms in the region.