Summary Blood chemistry profiles of cultured sturgeon hybrids Acipenser naccarii female × Acipenser baerii male were assessed in order to acquire basic data for evaluating fish health status on‐farm. Sixty healthy fish (11.0 ± 3.2 Kg weight; 117.8 ± 8.6 cm total length) were randomly captured from 600 m3 concrete tanks and sampled from April to June. Blood samples were analyzed for the following 22 biochemical parameters using standard clinical methods: cortisol, glucose, lactate, non esterified fatty acids, triglycerides, cholesterol, albumin, creatinine, urea, total bilirubin, total protein, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, creatine phosphokinase, lactate dehydrogenase, calcium, phosphorus, magnesium, sodium, potassium and chloride. Biochemical values were found to be consistent with data from the parental species A. naccarii. Cortisol, cholesterol, albumin, urea, total bilirubin, CK, LDH and magnesium were significantly affected by sampling time and the differences are probably related to sexual maturation of the fish. Blood chemistry analyses afforded an accurate evaluation of sturgeons’ health status, also providing information on their reproductive conditions. Evidence resulting from cortisol and lactate values indicated that pre‐sampling operations, including capture and confinement of these large‐sized fish, must be carefully managed in order to minimize handling stress. This study provides knowledge on blood chemistry of hybrid sturgeon A. naccarii × A. baerii and the results corroborate the validity of the test panel performed in evaluating the physiological functions of sturgeons. Reference values for 22 biochemical parameters were identified for the purpose of evaluating health and welfare in cultured sturgeons.

Sex and stage of gonad maturity in 6 year-old sturgeon hybrids (Acipenser naccarii female · Acipenser baerii male) were examined by means of ultrasonography, histology and sex steroid analyses during the reproductive season. Ultrasound images of gonads revealed male and female sturgeons at different stages of maturity, distinguished by gonad morphology and tissue echogenicity. Sexing and staging were found to be more difficult in immature fish, especially males, and ultrasounds were combined with sex steroids and histological analysis to confirm the sex and gonad developmental stage. Histology identified males and females at different developmental stages. Serum testosterone differed significantly between mature males and females (321 vs 15.4 ng ml )1 ) as well as 17b estradiol (0.4 vs 4.2 ng ml )1 ). High testosterone concentration was found also in immature sturgeon females. The male : female sex ratio was 1 : 1.5. Size was found to be significantly different between males (9.2 kg and 114.8 cm) and females (12.9 kg and 121.6 cm). Results indicate ultrasounds as a reliable, rapid and non invasive method to determine sex and maturity stages in hybrid sturgeon A. naccarii · A. baerii during the reproductive period, affording benefits to farmers for sex selection and breeding purposes. Further investigations are needed, in particular in immature individuals and outside the reproductive season, to identify sturgeon sex as early as possible.

Three anaesthetic agents were tested in sturgeon hybrid Acipenser naccarii female · Acipenser baerii male: clove oil at 100 mg L )1 (CLO); tricaine methanesulfonate at 150 mg L )1 (MS-222); combined medetomidine and ketamine hydrochloride (MK) administered by intravenous injection at 0.04 mg kg )1 + 4 mg kg )1 , respectively. Efficacy of the anaesthetics was evaluated as well as physiological effects on blood gas status, acid-base balance and stress response by measuring blood PCO 2 , PO 2 , pH, HCO À 3 , haematocrit and serum cortisol, glucose, NEFA, lactate, Na + , K + , Cl ) concentration. Anaesthetic dosages were safe and effective in order to rapidly anaesthetize the sturgeons: induction time was significantly shorter with MS-222 (3.2 min) compared with CLO (4.7 min) and MK (5.4 min). Recovery time was significantly longer in MK anaesthetized fish (16 min) in comparison with CLO (5.8 min) and MS-222 (3.8 min). Anaesthesia induced blood hypercapnia, respiratory acidosis and stress response, with differences among anaesthetics. Blood PCO 2 and cortisol levels were significantly higher in MS-222 (11 mmHg; 97.0 ng ml )1 ) and CLO (9.6 mmHg; 65.3 ng ml )1 ) anaesthetized groups compared to MK (7.8 mmHg; 39.6 ng ml )1 ) and control (7.0 mmHg; 10 ng ml )1 ). Overall results indicated that anaesthesia with MS-222 produced a greater physiological impact in sturgeons compared to the other anaesthetics. The effects were slightly attenuated in fish anaesthetized with clove oil, indicating that the use of this chemical was better than MS-222 in reducing handling stress. MK anaesthesia affected physiological parameters to a lesser extent. Intravascular administration of medetomidine at a dose of 0.04 mg kg )1 in combination with ketamine at a dose of 4 mg kg )1 proved to be a safe and effective anaesthetic protocol in this hybrid sturgeon, suitable for experimental studies and diagnostic procedures related to broodstock management and artificial reproduction.

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This study compared the nutrient-energy retention, digestive function, growth performance, and welfare of rainbow trout (ibw 54 g) fed isoproteic (42%), isolipidic (24%), fishmeal-free diets (CV) over 13 weeks. The diets consisted of plant-protein replacement with graded levels (10, 30, 60%) of protein from poultry by-product (PBM) and black soldier fly H. illucens pupae (BSFM) meals, either singly or in combination. A fishmeal-based diet was also tested (CF). Nitrogen retention improved with moderate or high levels of dietary PBM and BSFM relative to CV (p < 0.05). Gut brush border enzyme activity was poorly affected by the diets. Gastric chitinase was up-regulated after high BSFM feeding (p < 0.05). The gut peptide and amino acid transport genes were differently regulated by protein source and level. Serum cortisol was unaffected, and the changes in metabolites stayed within the physiological range. High PBM and high BSFM lowered the leukocyte respiratory burst activity and increased the lysozyme activity compared to CV (p < 0.05). The BSFM and PBM both significantly changed the relative percentage of lymphocytes and monocytes (p < 0.05). In conclusion, moderate to high PBM and BSFM inclusions in fishmeal-free diets, either singly or in combination, improved gut function and nutrient retention, resulting in better growth performance and the good welfare of the rainbow trout.