Effects of illumination on early life development and digestive enzyme activities in common pandora Pagellus erythrinus L. larvae

The activities of main digestive enzyme (proteases, amylase and lipase) and animal husbandry (mainly growth and survival) were studied in common pandora Pagellus erythrinus larvae until 30 days after hatching (DAH). Three different illumination levels (10, 30 and 100 lx) were compared in triplicate and green water technique was carried out. At the end of the experiment, illumination did not affect neither survival nor growth except 10 lx treatment. Similarly, specific growth rate (SGR) was different in 10 lx treatment (p < 0.05), although no differences were found in group 30 and 100 lx treatments (p > 0.05). In all groups, trypsin and chymotrypsin specific activities were firstly detected on day 3 related with mouth opening and slightly increased until 20 and 25 DAH respectively, and after this date specific activities of those decreased. Although, there was a significant difference between 10 lx treatment and other experimental groups (p < 0.05), no differences were found in other treatments (p > 0.05). Pepsin was firstly detected on day 25 related with stomach formation and sharp increase was observed until 30 DAH and then slight decrease was measured from this date and no differences were found between all groups. Amylase was firstly determined on day 2 and increased to day 5. After this date, slight decreases were measured in all groups and continued until end of experiments. The highest specific activity of amylase was determined in 30 lx treatment and no significant differences were found between groups (p > 0.05). Lipase was firstly detected on day 4 and increased to day 10. Then, activity of lipase decreased until day 15 and increased again until 25 DAH. Slight decreases were found in all groups until day 30 and continued to end of experiments. No significant differences were detected among groups (p > 0.05).

Finally, the significant improvement in survival, larval development and specific enzyme activities of larvae were determined in 30 lx treated group. It is thought that this phenomenon is related to optimal keeping conditions provided by the medium illumination level for Pagellus erythrinus larvae.     

Microsatellite variability in natural populations of the blackspot seabream Pagellus bogaraveo (Brünnick, 1768): a database to access parentage assignment in aquaculture

Eight microsatellite loci previously reported were assessed for their utility in parentage assignment in 96 individuals belonging to natural populations of the blackspot seabream Pagellus bogaraveo (Brünnick, 1768) from the Mediterranean and Northeast Atlantic regions. At the mtDNA level, no differentiation was found between these two regions but based on microsatellite data an overall discrete genetic differentiation is perceivable between the two regions separated by the Strait of Gibraltar. The number of alleles per locus ranged from 8 to 30. A database constructed with allele frequency data from six populations was used in a simulation parentage assignment test using the software cervus . The test showed that the number of markers used is enough to perform parentage assignments with real data. The polymorphic information content for each locus was very high (mean value of 0.849), with a total exclusionary power of 0.9995. In summary, seven of the eight microsatellites analysed proved to be sufficient and powerful tools for parentage assignment in hatcheries and the allele frequency data given here can be used to perform pedigree analysis against which real data may be tested.     

Temperature Preference of Early Developmental Stages of Pagellus erythrinus

Pagellus erythrinus culture was carried out from the fertilizable egg to the larval stage at different temperatures: 15°, 18°, and 21°C for the embryonic stage and 16°, 18°, and 21°C for yolk-sac and larval stages. Total length and variability, growth rate, duration of each stage, hatching percentage, survival of each developmental stage, efficiency of vitelline and lipid utilization, and the percentages of morpho-anatomical abnormalities were used as criteria for the evaluation of temperature's influence on culture of Pagellus erythrinus. A temperature of 18°C favors the early life stages culture of Pagellus erythrinus.     

Pagellus erythrinus (Common Pandora): A Promising Candidate Species for Enlarging the Diversity of Aquaculture Production

The euryhaline species Pagellus erythrinus was investigated for potential use in aquaculture. The research focused on the biological aspects of the species examining its adaptability in captivity, examining reproduction, brood stock construction, larval rearing and on-growing of the fingerlings, produced in cage culture under different diets and feeding regimes. Natural spawning resulted in the production of 150,000 viable eggs/kg with an average hatching rate of 85%, whereas spawning induced with injection of HCG hormone (500 and 250 IU/kg) produced 16,140 and 29,940 viable eggs/kg for the high and low dosage, respectively, with an average hatching rate of 75%. The culture of the fingerlings in floating cages in the region of Galaxidi (east central Greece) is also described. The results are encouraging in terms of a possible intensive culture of the species, but nonetheless further research on the reproduction and the larval rearing of the species is imperative.     

Effects of carbohydrate sources on growth,body composition and tissue lipid deposition of blackspot seabream,Pagellus bogaraveo (Brunnich)

Rearing blackspot seabream has been associated with low growth rates and excessive lipid accumulation, resulting in a reduction of the edible yield. The effect of extruded diets containing different carbohydrate sources (wheat vs. wheat bran) was evaluated on 100 g blackspot seabream growth performance, feed utilization and fat deposition, taking into consideration the optimal dietary protein and lipid level described for smaller‐sized fish. A fish meal‐based diet was also tested as a control to assure maximal growth rates were achieved. The experiment was held in sea cages at environmental conditions. Duplicate groups of fish were distributed among six cages with a stocking density of 1.3 kg/m³ and hand‐fed each diet for 7 months. At the end of the experiment, fish in all groups doubled their body weight attaining 190–230 g. Specific growth rate (0.3–04), feed conversion ratio (1.3–1.6) and protein gain (0.5–0.6 g/kg/day) were similar among treatments. The Hepatosomatic Index, the Viscerosomatic Index and final whole body composition did not vary significantly among dietary treatments; nevertheless, the inclusion of wheat bran induced a significant increase of liver lipid content and the highest mesenteric fat index. All diets were effective in reducing whole body and mesenteric fat compared with initial values.     

Deep water longline selectivity for black spot seabream (<Emphasis Type="Italic">Pagellus bogaraveo</Emphasis>) in the Strait of Gibraltar

Species and size selectivity of the deep water longline traditionally used in commercial fishing of the black spot seabream (Pagellus bogaraveo) were studied in the Strait of Gibraltar with four sizes of hooks. Black spot seabream contributed up to 88% of the catch by number. Catch and by-catch rates differed for the different hooks and fishing trials. Significant differences in average fish length between all hooks, except in one case, were found. The comparison of two experimental fishing trials within 4 years indicates a displacement towards smaller sizes in the size frequency distributions. The results of this study show that the fishing gear can be size selective depending on hook size. The fitted selectivity models for each experiments were very different despite having two hooks in common. This is probably due to the very different catch size distributions in the two periods, which suggests that the population size structure changed significantly between 2000/2001 and 2004/2005.     

Nutritional quality of amino acid in farmed,farm‐aggregated and wild Axillary seabream (Pagellus acarne) with implications to Human Health

This study evaluated the nutritional quality of farmed and wild axillary seabream (Pagellus acarne R., 1827) focusing on amino acid profiles, with regards to possible interactions with wild fish aggregating around the cage facility. Total amino acids (∑AA), essential amino acids (∑EAA), non‐essential amino acids (∑NEAA) and neutral amino acids (∑NAA) in farmed fish were lower than those in the wild individuals (p > .05). Amino acid pattern in cage‐aggregated fish showed a slight decline from the wild populations, but still higher than the farmed fish. Based on the amino acid scores (AAS), lysine and leucine could be underlined as the ‘first limiting amino acids’, but all other AASs were over ‘1’, in accordance with reference amino acid contents of FAO/WHO (>1.00), showing that farmed axillary seabream provides high nutritional quality and can be considered as a favourable protein source. The ratios of ∑EAA/∑AA (44%–46%) and ∑EAA/∑NEAA (79%–86%) exceeded the minimum recommendation of 40% and >60% by FAO/WHO for all three groups. It can be concluded that axillary seabream either farmed, farm‐aggregated or distant wild fish presented high‐quality protein generating a healthy source for human food.     

Influence of temperature on muscle fibre hyperplasia and hypertrophy in larvae of blackspot seabream,Pagellus bogaraveo

The effects of temperature on Pagellus bogaraveo muscle cellularity were investigated, by morphometry, throughout the endogenous feeding stage, testing two rearing temperatures: 14 and 18 °C. The following parameters were estimated in transversal body sections at post‐opercular and post‐anal body levels: the total cross‐sectional muscle area, the total number of fibres and the mean cross‐sectional fibre area. At hatching, no significant influence of the temperature was observed on the morphometric parameters measured in the white muscle. At mouth opening, an increase in the number of post‐opercular white fibres was promoted by the highest temperature. During embryonic development, the red muscle fibre number in the post‐anal part of the larvae increased with higher temperature, but it appears that the difference was no longer present at mouth opening. An increase in the fibre area and in the total cross‐sectional area of red muscle at the post‐anal level was promoted by a 4 °C increase in the temperature during the vitelline phase. In conclusion, the axial musculature of blackspot seabream embryos/larvae reacted differently to temperature influence according to the body location, strongly supporting the need to look at and account for different body locations when evaluating muscle cellularity in fish, namely in growth/aquaculture‐related studies.     

Ontogenic development of the digestive enzymes in common pandora, Pagellus erythrinus, L. larvae

Ontogenic development of some digestive enzymes (proteases, amylase and lipase) in common pandora Pagellus erythrinus larva was assayed during larval development. The green‐water technique was employed for larval rearing, and whole‐body homogenates were used for enzymatic assays in triplicate. Important alterations in specific activities of all digestive enzymes measured during the period of this study were mostly related to metamorphosis and weaning. Mouth opening was observed on day 3 at 2.23±0.01 mm total length synchronously with the first determination of trypsin and chymotrypsin activities. After this date, the specific activities of these slightly increased until 25 days after hatching (DAH), respectively, and then slightly decreased and changed. The pattern determined for pepsin was strongly related to stomach formation on day 25 at 9.72±2.3 mm total length and a sharp increase was found until 30 DAH and then a slight decrease was measured from this date until the end of the experiment. Both amylase and lipase were measured for the first time on days 2 and 4, respectively, and also the specific activities of these showed similar patterns during the first week of the study. Then, slight variations were observed until 30 DAH and while lipase‐specific activity had declined, an increase in the specific activity of amylase was found until the end of the experiment. Finally, it is thought that the variations observed in the specific activity in the profile of digestive enzymes were related to either metamorphosis such as formation of stomach (25 DAH) or to changes in characteristics of food (30 DAH). The pattern of development of the main digestive enzymes found in P. erythrinus is similar to that described in other Sparid species.