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Survival rate, sex ratio and zootechnical performances were evaluated on 168 kg of Anguilla anguilla elvers (0.45 gj weaned into three groups (Al, A2, A3) at initial densities of 800, 1600 and 3200g m-j, respectively. In order not to modify the sex ratio, animals weaned at the different densities were maintained separately during the trials, and no size grading was performed at the fattening phase.Final mean weight achieved by females belonging to the different groups showed no statistically significant differences; weight of males was higher (P < 0.05) in A1 than in A3 where a higher percentage of males was observed. Sex ratio of eels was different among the groups, with a higher percentage of males in A3 (96%) than in A2 (78%) or in Al (69%). This finding testifies to a sex differentiation strongly affected by pre-fattening stocking density of elvers. Final load showed an increase in males corresponding to a significantly reduced biomass between A1 and A2 (10.97 and 10.24kg m-3) and A3 (8.44kg m-3). Final survival rate ranged from 87% ( A l j to 90% (A3). As to food conversion, a better rate was found in A1 (1.9:l) compared to A2 (2.1:l) and A3 (2.3:lj eels.

Seabass (SBS) and seabream (SBM) juveniles were reared with the goal of obtaining three different final densities (SINT ¼ 40 kg m )3 ; INT ¼ 20 kg m )3 ; SEM ¼ 0.2 kg m )3 ) to ascertain the effects thereof on the welfare of the fish. Significant blood metabolites and hepatic glycogen were determined every 3 months and at harvest. Trials lasted 18 months in seabass and 17 months in seabream. At the end of experiment the main biometric productive parameters and quality of body composition were also recorded. Regarding intensively reared seabass (SINT-SBS, INT-SBS), the plasma triglycerids, total cholesterol and transaminases (AST, ALT) were always significantly higher than in semi-intensively maintained fish (SEM-SBS). At the final sampling in the SINT-SBS batch, the total protein and glucose were also markedly increased. Conversely, at harvest the liver glycogen content decreased in SINT-SBS (34 ± 8 mg g )1 liver) with respect to INT-SBS (57 ± 12 mg g )1 liver) and SEM-SBS (63 ± 11 mg g )1 liver). No differences among groups were observed for creatine kinase (CK) and lactate dehydrogenase (LDH). With regard to seabream, SINT-SBM and INT-SBM constantly showed plasma triglycerids and total cholesterol as being significantly higher when compared to SEM-SBM. In the final two blood samplings, SINT-SBM exhibited the most elevated values for LDH. At harvest, AST, ALT, total protein and glucose markedly increased in SINT-SBM, whereas liver glycogen content was reduced (22.5 ± 9 mg g )1 liver), more than in INT-SBM (70 ± 16 mg g )1 liver) and SEM-SBM (75 ± 20 mg g )1 liver). In both seabass and seabream, body composition was very similar in the different stocking densities, except for total cholesterol. Total n-3 polyunsaturated fatty acid (PUFA) in seabream was significantly different from fish of the semi-intensive groups; however, nutritional values and fatty acid profiles were equally good. The intermediate final density of seabass and seabream at 20 kg m )3 seemed to give the best results in terms of their well being when compared to fish reared at 40 kg m )3 . The absence of differences in blood metabolites and hepatic glycogen levels between the intensive batch and the semi-intensive groups until harvest was a reference to the positive status of the fish. A density of 20 kg m )3 can be considered acceptable for farm strategy planning for raising healthy on-growing seabass and seabream juveniles.

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This study aimed to compare the fertility of eggs between artificially matured female silver eels that spawned spontaneously and those that were spawned by manual stripping. The effects of the two methods of spawning on ovulation and fertilization rate were also investigated. For this purpose, 18 wild female European eels captured in Bonello lagoon (North Adriatic Sea) were carp pituitary extract‐injected to undergo sexual maturation and ovulation; a final injection of 17,20β‐dihydroxy‐4‐pregnen‐3‐one (DHP) was administered when at least 30% of the oocytes were fully transparent. After the DHP‐injection, nine eels were transferred to a new closed recirculating aquaculture system, where they were housed with spermiating males (sex ratio 4/1) to allow spontaneous spawning (SPT‐group); the remaining nine eels were transferred to a 250 L tank and ovulation was checked at four‐hourly intervals by manual stripping (STR‐group). The number of eggs per female in the SPT‐group was significantly greater than that in the STR‐group. Furthermore, fertilization rates in the SPT‐group were notably higher than those observed in the STR‐group. Significantly, the best performances were obtained among eels in which at least 50% of oocytes were fully transparent at the time DHP was administered. We conclude that the fertility of eggs from spontaneously spawning eels is superior to that of eggs acquired by strip‐spawning and artificial fertilization.