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Abstract The egg quality of two common dentex captive broodstocks were monitored for two consecutive years during their natural spawning season. Volume of spawned eggs, volume of buoyant eggs, fertilization rate, egg weight, hatching rate and mortality of larvae were recorded. According to the volume of spawned eggs, the ratio of buoyant eggs spawned, the number of spawning days and the fertilization rate pointed to an improvement from Year 1 to Year 2. But data on hatching rate and larval mortality lead to the opposite conclusion. Highlights • Two common dentex captive broodstocks have been monitored during their natural spawning season for two consecutive years. • The quality of the spawned eggs has been assessed using different quality criteria based on egg production or larval performance. • Criteria used for assessing the spawning quality lead to different conclusions. • In conclusion, all criteria should be used in order to obtain a reliable assessment, including criteria based on larval performance. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this study was to assess the potential effects of replacing part of the dietary protein by lipid or carbohydrate on the characteristics of dentex muscle. Dentex were hand-feed four isoenergetic diets (22.6 MJ kg−1 gross energy) with protein:lipid:carbohydrate ratios 43/16/28 (D1); 43/24/4 (D2); 38/19/28 (D3), and 38/24/13 (D4). At the end of the feeding period, biometric parameters, textural properties of muscle, as well as protein, lipid and collagen contents, and electrophoretic protein profiles of this tissue were studied. The decrease in dietary protein content improved textural parameters (increased firmness and water holding capacity). Within each dietary protein level, diets with high carbohydrate and low lipid contents resulted in lower values of muscle firmness than diets with low carbohydrate and high lipid contents. This increase in firmness matched with a lower muscle lipid and higher muscle collagen contents. SDS-PAGE separation of muscle extracts showed a higher relative contribution of myosin to total optical density in muscle from those animals fed lower dietary protein, although no significant difference in fish texture could be attributable to this finding. Results indicate a favourable effect of replacing protein by alternative energy sources (lipids or carbohydrates) on the rheological properties of muscle in this species, this improvement was more noticeable when protein was replaced by lipid than by carbohydrate. [Copyright &y& Elsevier]

Abstract: The digestive physiology of common dentex was studied by assessing the activity of different pancreatic (trypsin, chymotrypsin, amylase and lipase), intestinal (alkaline phosphatase, aminopeptidase N, maltase and leuncine–alanine peptidase) and gastric (pepsin) enzymes from hatching until the juvenile stage (50 dph at 19 °C). Enzymes involved in the digestion of protein, lipid and carbohydrate were present in common dentex larvae at hatching and before the onset of exogenous feeding. The specific activity of trypsin and chymotrypsin in newly hatched larvae was higher than that of amylase and lipase, indicating the importance of these enzymes in the cleavage of yolk proteins and hatching, while after hatching, the activity of these serine proteases dramatically decreased, whereas lipase showed the opposite trend. A progressive shift in activity from alkaline to acid proteases was observed during larval development, reflecting that alkaline proteases were not longer the main digestive enzymes involved in protein digestion after the development of gastric glands and onset of acidic digestion. Lipase total activity in common dentex peaked at 35 dph and decreased after weaning. Diet change due to weaning might partially explain the decrease in lipase activity, although this change might be also indicative of a change in the nutritional requirements of this species, since the juveniles prefer diets with high protein levels than those with lower protein and higher lipid content. Regarding intestinal enzymes, leucine–alanine peptidase and alkaline phosphatase and aminopeptidase N were found in newly hatched larvae, while maltase was detected after the onset of exogenous feeding. The achievement of an efficient brush border membrane digestion takes place much earlier (6–12 dph) than in any of the studied species which might reflect the different metabolic profile and rapid growth of this species. [Copyright &y& Elsevier]

Abstract: The spawning quality, in terms of hatching rate, larval mortality at 3 and 5 days post-hatching (dph) and day of total mortality of two broodstock groups of common dentex was evaluated for 1 month in 2005. Several biochemical parameters including total lipid content, lipid class and fatty acid composition, carbohydrate content and metabolic enzyme activities were analysed in all the egg batches collected. Comparison was carried out between low- (mortality at 3 dph higher than 35%) and high-quality (mortality at 3 dph lower than 10%) batches. No differences were observed in lipid content and/or lipid class and fatty acid composition although a slightly higher content of neutral lipids was detected in high-quality batches. However, significant differences were obtained regarding carbohydrate composition and the activity of enzymes such as alkaline phosphatase and pyruvate kinase being higher in low-quality egg batches. [Copyright &y& Elsevier]

Abstract: Skin coloration patterns in fish are of great physiological, behavioural and ecological importance, can be considered as an index of animal welfare in aquaculture and as an important quality factor for the retail value, especially of red skinned fish. In the present study we developed an appropriate method for comparisons of the skin chromaticity parameters in wild (Pagrus pagrus, Pagrus caeruleostictus, and Dentex gibbosus) and farmed red skin Sparidae and investigated the effect of storage time on skin colour of farmed Pagrus pagrus. The three-dimensional characteristics of colour appearance (lightness — L ⁎, hue — H° ab and chroma —C ab ⁎) were calculated. A new index, named Entire Colour Index (ECI), was developed to express hue and chroma which as combined variables, cannot be considered separately. In all species there was a remarkable dorsoventral gradient in mean L ⁎ and H° ab , with the ventral area being statistically significant brighter than the dorsal one. ECI value was species specific but did not show any statistically significant dorsoventral gradient, with the exception of P. pagrus. Skin melanin and carotenoids content presented differences between the Pagrus and the Dentex species that may explain the differences in the observed chromaticity pattern. Storage time affected lightness and hue only in the dorsal skin area. However, the effect of storage on ice was better reflected in mean ECI value which showed a marked decrease from Day 3 to Day 7 in both the dorsal (Day 0: 8.96±0.40; Day 7: 2.86±0.29) and ventral (Day 0: 8.97±0.18; Day 7: 4.10±0.29) skin area. Our results provide data for a non-subjective determination of skin colour pattern and show that ECI offers a good index of the actual colour in a meaningful and objective way. [Copyright &y& Elsevier]

This study describes the evolution of tissue composition and serum metabolites of common dentex (Dentex dentex) in different maturity stages. During maturation, diet and perivisceral fat provide the materials needed for the development of gonads. Female and male fish had higher total proteins, total fat, triglycerides (TG) and cholesterol in their serum, at spawning and spermiation, respectively. The examination of dentex tissues (muscle, liver and gonad) revealed no statistically significant differences (P<0.05) in energy density and lipid content during different maturity stages and there was no conclusive evidence that energy density and lipid content differ between sexes. In muscle, liver and gonad triglycerides fraction, the proportion of saturated fatty acids (FA) was greater than the proportion of polyunsaturated fatty acids (PUFA), whereas the reverse observation was made (with the exception of liver) in the polar lipid (PL) fraction of the above tissues. In muscle and liver, the main polyunsaturated fatty acids (n-3 PUFA) were docosahexaenoic (DHA, 22:6n-3) and eicosapentaenoic (EPA, 20:5n-3) acids. The main n-6 polyunsaturated fatty acids were linoleic (18:2n-6) and arachidonic (20:4n-6) acids. Palmitic (16:0) and oleic (18:1n-9) acids were the main saturated fatty acids and monoenes, respectively. The relative concentration of the major fatty acids varied seasonally and a pattern can be seen in both mature and immature dentex. In the PL fraction of muscle, higher values of total saturated and n-3 fatty acids, palmitic acid and DHA were obtained during summer in comparison to winter samplings; this trend was also shown by the total saturated fatty acids in the TG fraction. [Copyright &y& Elsevier]

Dentex is considered suitable for aquaculture due to its ready adaptation to culture systems, acceptance of formulated feeds and rapid growth rates. However, little information on the nutritional requirements or growth rates under controlled conditions has been reported for this fish. Thus, two feeding trials were performed, at different growth stages, to identify suitable protein and lipid (energy) levels to be used in formulating dry diets for this species. As the first step, a 3×2 factorial experiment was conducted to determine the optimum protein-to-energy (P/E) ratio for fingerling dentex. Triplicate groups were fed to satiation one of six practical diets with increasing levels of protein (50%, 53% and 57% DM) and two energy levels (20 and 22 kJ g-1) within each protein level. Protein utilization was enhanced by a sparing effect of dietary lipid at 19.7%. These data suggest that, when the energy level of the diet is maintained at 22 kJ g-1, the dietary protein level for fingerling dentex can be lowered from 57% to 50%. In the second experiment, with larger fish, triplicate groups of fish were fed one of six diets with two energy levels (20 and 22 kJ g-1) and three P/E ratios (19, 21 and 23 g MJ-1). Thus, the dietary protein level tested ranged from 38.7% to 51.14% DM. The results in the second trial suggest that, when protein efficiency or retention are considered, even dietary levels of 43.4% CP and 19 g protein MJ-1 of P/E, and a calculated available energy level (22 kJ g-1) could be assumed to be adequate levels for formulating practical diets for this species at this growth stage. It can be concluded that, for the two size classes of dentex used, dietary lipid had a protein-sparing effect. [Copyright &y& Elsevier]

Dentex fingerlings weighing 2.5 g initial live weight were fed 12 extruded diets containing four crude protein levels (40%, 45%, 50% and 55%) and three crude lipid levels (12%, 17% and 22%) according to a factorial design, for 6 weeks. Survival was high (84–92%) and specific growth rate (SGR) values were 3.4%, 3.9%, 4.3% and 4.1% day−1 and food conversion ratio (FCR) were 2.2, 2.1, 1.5 and 1.9 for fish fed the diets containing 40%, 45%, 50% and 55% crude protein, respectively. With respect to lipid levels, SGR values were 4.2%, 4.0% and 3.6% day−1 and FCR were 1.7, 1.8 and 2.3 for 12%, 17% and 22% crude lipid, respectively. The effects of protein and lipid levels were significant; final live weight, SGR, FCR and PER values were best for fish fed 50% crude protein and poorest for those fed 22% lipid diets. The best growth performance was observed in fish fed diets containing 50/12 and 50/17 protein/lipid ratios. The results indicate that optimum growth and nutrient utilisation of dentex fingerlings can be obtained when they are fed a diet containing around 50% crude protein with a lipid level ranging from 12% to 17%, and having a crude protein/gross energy ratio from 22 to 25 g MJ−1. [Copyright &y& Elsevier]