Search

The reproductive performance of Octopus vulgaris broodstocks fed two different diets (mixed fish [F group, BW 1,048.14 g] or mixed crustaceans [C group, BW 998.44 g]) was analyzed using an experimental recirculating aquaculture system consisting of a tank equipped with spawning and incubation chambers. A total of 8 females (F1–4; C1–4), and 8 males (M1–M8) were selected. DI of the C group females was significantly (p

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 els captured in Bonello lagoon (North Adriatic Sea) were carp pituitary extract-injected to undergo sexual maturation and ovulation; a final injection of 17,20b-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 STRgroup. 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.

Inclusion of sustained-release androgen implants into fertility treatment regimes of female freshwater eels has been proposed to benefit artificial maturation outcomes. This study sought to test whether co-administration of the androgen 17-methyltestosterone (17-MT) in combination with ‘traditional’ hypophysation of female European silver eels would affect egg quality and subsequent larval survival. Implants, containing 1 mg 17-methyltestosterone (17α-methyl-4-androsten-17β-ol-3-one in a matrix of cholesterol:cellulose = 95:5), were administered twice, at 1 and 5 weeks after onset of experimentation (MTA- and MTB-groups); control eels (Ctrl) were given a blank implant. Female eels received weekly injections with carp pituitary homogenates (CPH) from either Week 1 (MTA- and Ctrl groups) or Week 5 onwards (MTB-group). First 4 injections were made with 10 mg CPH/kg body weight (BW) in sterile physiological saline (0.9% NaCl); the subsequent 12 injections with 30 mg/kg CPH and thereafter, 40 mg/kg CPH was injected until fish were considered ready for induction of final maturation. Bi-weekly blood samples were collected (Day 0 onwards) and analyzed for levels of testosterone (T) and estradiol-17β (E2) by radioimmunoassay. After reaching maturity, fertilized eggs were obtained upon spontaneous spawning of co-housed breeders and egg performance (fertilization, hatching, survival rates) was recorded. No differences were observed between eels from the MTA- and MTB-groups; however, egg performance was notably better in eels treated with 17-MT + CPH compared to eels receiving CPH only, with hatching rates reaching mean values as high as around 70% for both 17-MT and CPH co-treated groups, but only averaging 21.0 ± 8.4% for eggs from the Ctrl-group. Furthermore, 17-MT treated eels displayed a more distinct pre-spawning peak for levels of plasma T and E2 and for body weight, the latter being indicative of increased batch fecundity. We conclude that androgen co-treatment holds promise for future development of eel captive breeding technologies. Statement of relevance Artificial propagation of the European eel is increasingly urgent to release the strain on natural populations. This study presents a novel approach to artificial maturation of female eels: centered around the incorporation of androgens during fertility treatment. Accordingly, increased performance was observed in terms of fertilization, hatching and survival rates, which contributes to completing the life cycle of this fish in captivity. © 2017 Elsevier B.V.

The objective of the present study was to obtain spontaneous reproduction in captivity of the European eel ( Anguilla anguilla ) by using a new closed recirculating aquaculture system provided with spawning and incubation chambers. The influence of two levels of water-flow rates (Low-Flow: 0.8 ± 0.05 L/s and High-Flow: 2.4 ± 0.05 L/s) on the spawning, fecundity and egg quality was also investigated. For this purpose 12 silver eel females were induced with increasing doses of carp pituitary extract (10, 20, 30 and 40 mg CPE/kg BW). Twenty-four hours after the last CPE injection, each female ovulation was induced by injecting a DHP-solution and then transferring them to a new closed recirculating aquaculture system, where they were maintained for 16 h with spermiating males (sex ratio 4/1) in order to obtain spontaneous reproduction. The reproduction was tested with 6 females in Low-Flow rate conditions and 6 females in High-Flow rate conditions. The results showed that the designed closed-loop system made it possible to carry out a more spontaneous reproduction for more than 80% of the females that underwent standardized gonadotropic treatment and favored the automatic and complete transfer of the eggs to the hatchery. The results also point out that high or low water current conditions in the tank do not hinder the mating and the emission of gametes by the breeders, but the High-Flow rate in the two incubation chambers showed unsuitable hydrodynamic conditions for embryonic development resulting in a constant loss of viable eggs which reached a mortality of 100% among females with the highest incubation density.

A trial was conducted to evaluate the growth performance and survival of common catfish, Ameiurus melas. A total of 54,420 catfish juveniles (5.1 ± 1.2 g; 6 ± 1 cm) were reared in two groups: PN group, represented by 3-1,000 m2 ponds; RC group composed by 3-2 m3 indoor tanks working in closed recirculated system. In these two groups, catfish were reared at two different densities (PN=15 fish m3 ; RC=1,570 fish m3 ) for 181 days. The main water physico-chemical parameters were monitored and the main blood metabolites and growth performances were evaluated. Catfish exhibited a final mean body weight similar in the two groups (PN=142.7 ± 30 g; RC=151.5 ± 34 g). The survival rate was high for both PN (86.6%) and RC (99%). A very high stocking density was reached in the RC system (235.5 kgm3 ). The presence of multi-trays in the RC tanks may be helped the specimens to reduce aggressiviness and territorial competition as demonstrated by blood metabolites which did not affect by rearing conditions. This trial showed that common catfish can be successfully cultured in indoor systems without negatively affecting productive performances (growth and survival) and the natural resources.

This study evaluated the growth performance and survival rate of Anguilla anguilla glass eels reared in 4750 m2 earthen ponds and dependent on trophic resources provided by natural macrobenthic populations. Two ponds (M ponds) had mostly muddy-soil bottom whereas the other two (S ponds) had mostly sandy-soil bottom. A total of 4795 pigmented glass eels (0.73 ± 0.26 g) were stocked, at a density of 1.6 fish/m2 . After 360 days of growth, in S ponds eels exhibited a final mean body weight (15.57 ± 5.36 g) significantly higher than those seeded in M ponds (9.85 ± 4.11 g). Mean final length of S eels (21.55 ± 3.33 cm) was statistically higher than that of M eels (17.85 ± 2.42 cm). In M ponds, relatively higher abundances of Crustacea appeared to promote higher survival of glass eels in the post-seeding phase. Consequently, the relatively higher densities of eels in M ponds could have resulted in slower growth compared to eels in S ponds; however, eels grown in M ponds exhibited a significantly higher conditioning factor at the end of the growth period. We conclude that M ponds host highly viable macrobenthic prey populations that better sustain the early growth phases of A. anguilla . Furthermore, this study demonstrated that artificial feed supplements are not necessary for the rearing of A. anguilla juveniles in earthen ponds.

This study aimed to describe the response variability of females silver eels in terms of gonad development and eggs production to standardized gonadotropic treatment (Carp pituitary extracts -CPE), and to relate this variability to population characteristics. For this purpose, sexual maturation, ovulation and fertilization were induced in two eel populations coming from different locations in Adriatic Sea (Comacchio -CM and Marano-Grado -MG lagoons), and after that, their reproductive capacity was valuated. External (Silver index -SI, Eye index –EI, Pectoral fin length index –PFLI, Condition factor -K) and hormonal (17β-estradiol -E2, testosterone -T) parameters were measured and some subject/group were sacrificed for histological and lipid analysis and age determination. Morphometric parameters showed the CM-Group to have highest values of Body weight (BW), Body length (BL) and K, while MG-Group presented highest PFLI and Gonadosomatic index (GSI) values. Regarding hormonal analysis, the CM-Group showed significantly higher T and E2 levels than the MG-Group, both groups showed considerably rapid increase at T5 (5th injection). A positive trend in gonadal development was found through histological evaluation; a more regular maturation was observed in the MG-Group whereas the CM-Group presented an exponential oocytes development starting from T10 (10th week), which led to an anticipated spawning. Lipid content showed significant differences in T0 (start study), post-ovulation and Control (30th week) between CM and MG eels. As to zootechnical performances, while MG eels released spontaneously into the water the CM’s were stripped in order to check ovulation. The MG eels were statistically the most productive with 40.1±6.33% BW of eggs released. Furthermore CM females ovulated mainly between the 19th and 22nd week (77.8% spawned eels) instead in the MG’s ovulation goes from the 24th to the 28th week (100% spawned eels). As fertilization is of concern, in both groups fertilized eggs were obtained with no difference in larvae production. These results seem to indicate that bigger dimensions, higher K and larger lipid content (Comacchio eels) could fasten gonadic maturation without positively influence reproductive performance of animals, both in term of quantity and quality of produced eggs. Smaller females with a highest SI (Marano-Grado eels) presented a more regular gonadic development, leading the animals to spontaneous spawning

Summary Seabass (SBS) and seabream (SBM) juveniles were reared with the goal of obtaining three different final densities (SINT = 40 kg m−3; INT = 20 kg m−3; SEM = 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.

Growth performances of sunshine bass (initial m.b.w.=200±50 g) were examined in 3 different rearing conditions: concrete square basins (HSB-1); raceways (HSB-2); natural ponds (HSB-3). Fish received the same extruded feed (prot. 48.8%; lip. 17.8%). The trial lasted 16 months in HSB-1 and HSB-2 and only 12 months in HSB-3 due to unfavourable welfare status and low growth performances. At harvest (after 16 months), sunshine bass reached a satisfactory mean weight with- out significant differences between groups. HSB-2 fish were longer with a smaller circumference, prob- ably due to different hydrodynamics of the raceway. Glucose, cholesterol, triglycerides, protein, lactic dehydrogenase (LDH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), creatine kinase (CK), glycogen of plasma or tissue were not affected by rearing conditions as well as the proximate composition and the fatty acid profile of the fillet.

Summary 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% (Alj 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.

Two experiments were performed in an hatchery; in the first 520 sole larvae, average live weight (a.l.w.) 37 mg, 52 dah, were distributed among 8 net cages and fed two microdiets, for 55 days (d). Protein, fat, EPA contents were: 64.1 and 62.6; 21.9 and 18.5% on d.m.; 8.9 and 9.0% of fat respectively for diet A and B. Artemia enriched naupli (AEN) were distributed for 28 d, at 5 (1st week), 3 (2nd w.) and 2 units/ml (3rd and 4th ws.). In the secon trial 1040 sole larvae, a.l.w. 69 mg, 87 dah, were distributed among 16 net cages (4 replicates, diet A and B,8

The productive performances and morphological traits of 60 000 Dicentrarchus labrax L. weighing 2.4 ± 0.6 g and obtained from intensive rearing were compared with 60 000 sea bass of the same age (110-day-old) weighing 2.1 ± 0.7 g obtained from a fish farm using the mesocosm technique during the larval phase. The trial lasted throughout the fattening period until harvest. Fish from the mesocosm system (SB-II) had a better final survival rate (69%) in comparison to those obtained from the intensive larval system (64.2%) (SB-I). No significant differences emerged between the two groups concerning the specific growth rate (SGR) or the feed conversion ratio (FCR). Although the weights were the same as the SB-I group, the final total length result was higher in the SB-II group (P