This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.A C C E P T E D M A N U S C R I P T Skeletal anomalies in reared dusky grouper juveniles ACCEPTED MANUSCRIPTThe first attempts to reproduce dusky grouper (Epinephelus marginatus, Lowe 1834) under controlled conditions started in 1995, but the egg and larvae quality was very low. Mass production is still encountering many difficulties, mainly concentrated in the larval period when very high mortality rates are observed, confirming what has been observed in the rearing of other grouper species. The main bottlenecks have been identified as the difficulty to properly nourish the larvae, stress shock syndrome, and the high deformation rates.We analysed 633 dusky grouper larvae and juveniles (0.2-7.2 cm total length, TL), sampled during two larval rearing cycles carried out in 2001 and 2002 in Italy. The specimens at different development stages were stained in toto for bone and cartilage and examined for skeletal anomalies during dusky grouper ontogenesis. The incidence of anomalies in groupers hatched from the same egg batch but reared using two different methods (green waters and semi-intensive rearing) and three stocking densities (8, 16 and 28 larvae/l) was compared, with a view to providing tools for identifying the most appropriate larval rearing method in order to at least limit the onset of skeletal anomalies.Our results suggest that during development no particular skeletal anomaly patterns (or fate) can be clearly identified as a high variability was observed in malformation typologies and the regions affected.No significant differences in the morphological quality between groupers reared using semi-intensive (LV02 lot) and green water (GW02-01 lot) methodologies were observed, whilst groupers reared at the highest stocking density (28 larvae/l) showed the highest frequency of deformed individuals (75.8%), the highest malformation charge (average of 5.5 anomalies per deformed individual), the largest range of anomaly typologies (38), and the highest incidence of individuals with at least one severe anomaly (30.9%). Whilst in green waters no evident effects of larvae density were observed on survival rates, the survival rate in large volume reared individuals (17.5%) was considerably higher with respect to those reared in green waters (0.2%) at 7-8 larvae/litre. This indicates that the semi-intensive methodology should be considered more effective in enhancing the survival rate of dusky grouper larvae.
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.
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