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- Improving weaning strategies for Senegalese sole: effects of body weight and digestive capacityPublication . Engrola, S.; Conceição, L. E. C.; Dias, L.; Pereira, R.; Ribeiro, Laura; Dinis, Maria TeresaTo optimize Senegalese sole-weaning strategies, three experiments were performed.The first trial tested four weaning strategies with a10mg sole. Artemia-fed sole grew threefold less than fish fed an inert diet. Sudden weaning (abrupt change from Artemia to inert diet) and weaning with co-feeding produced larger sole than did a late weaning treatment; delayed weaning negatively affected ¢sh growth. In the second experiment, the digestive capacity of early-weaned 1, 2 and 4mg sole was investigated. The highest growth was observed in sole weaned at 4mg. Digestive enzyme pro¢les suggest that sole have an adaptation period to inert diets, with reduced feed intake. This adaptation period is inversely proportional to post-larvae weight. The third experiment examined weaning with cofeeding at di¡erent weights (2,5 and11mg).These studies demonstrate that sole of 5^10mg can be weaned, with high survival rates. On the basis of the digestive enzyme pro¢les, the early introductionof inert diets in co-feeding with Artemia seems to affect intestinal processes in smaller postlarvae. This study also suggests that trypsin and alkaline phosphatase may be used as indicators of nutritional status in sole ofo5mg.
- High stocking density induces crowding stress and affects amino acid metabolism in Senegalese sole Solea senegalensis (Kaup 1858) juvenilesPublication . Costas, B.; Aragão, C.; Mancera, J. M.; Dinis, Maria Teresa; Conceição, L. E. C.; Refojos, B. C.Fish held at high stocking densities are generally exposed to chronic stress situations that impose severe energy demands and may predispose the ¢sh to infection. Senegalese sole Solea senegalensis (Kaup) juveniles (78.8 18.9 g body weight) were maintained at low (LSD; 4 kg m2 at the end of the experiment), medium (MSD; 9 kg m2 ) and high (HSD;14 kg m2 ) stocking densities during a period of 63 days. Although disease outbreaks were observed in ¢sh reared at HSD, growth and food consumption did not vary among di¡erent treatments. Results from plasma cortisol and free amino acids (FAAs) showed signi¢- cant di¡erences among di¡erent rearing densities pointing to HSD as stressful rearing condition.
- Comparing skeletal development of wild and hatchery-reared Senegalese sole (Solea senegalensis, Kaup 1858): Evaluation in larval and postlarval stagesPublication . Gavaia, Paulo J.; Domingues, S.; Engrola, S.; Drake, P.; Sarasquete, C.; Dinis, Maria Teresa; Cancela, LeonorThe Senegalese sole is a marine pleuronectiform that naturally occurs in Southern Europe and Mediterranean region where it is being produced in aquaculture, in particular in Portugal and Spain. The aim of this study was to assess the quality of hatchery-reared larvae in comparison with those reared in the wild, and determine to which extension wild growing larvae are also affected by skeletal deformities. The main structures affected included those forming the axial skeleton, the caudal fin complex and both anal and dorsal fins, with the most prevalent anomalies affecting caudal vertebrae and arches. Hatchery-reared fish presented a higher incidence of deformities (79%) compared with the 19% observed in wild specimens. In wild postlarvae collected in Autumn no deformities were observed. This work clearly shows that wild Senegalese sole present less skeletal deformities than those hatchery-reared during larval stages, indicating a selective mortality of wild deformed fish and/or an effect of aquaculture-related rearing conditions in the development of skeletal deformities in sole.
- Effect of pre-weaning feeding regime on weaning performance of Senegalese sole, Solea senegalensis (Kaup, 1858)Publication . Engrola, S.; Conceição, L. E. C.; Gavaia, Paulo J.; Cancela, Leonor; Dinis, Maria TeresaDespite much interest in the production of Senegalese sole (Solea senegalensis) in southern Europe, weaning of this species onto artificial diets is problematic and varying results are obtained. The aim of this study was to test two feeding frequencies during a 13-day pre-weaning period and assess their impact on the growth and survival of Senegalese sole. Postlarvae were fed Artemia metanauplii with a peristaltic pump every hour for 12 hours per day or twice daily (morning and late afternoon). Both groups were suddenly weaned onto a commercial diet for an additional 30 days. At the end of the experiment, the relative growth rate and final dry weight were significantly higher and the survival significantly lower in the 12-hour treatment than in the twice-daily treatment. The feeding frequency had no effect on condition factor. The incidence of deformities was about 80% in both treatments.
- Effects of pre-weaning feeding regime on weaning performance of Senegalese sole, Solea senegalensis (Kaup, 1858)Publication . Engrola, S.; Conceição, L. E. C.; Gavaia, Paulo J.; Cancela, Leonor; Dinis, Maria TeresaDespite much interest in the production of Senegalese sole (Solea senegalensis) in southern Europe, weaning of this species onto artificial diets is problematic and varying results are obtained. The aim of this study was to test two feeding frequencies during a 13-day pre-weaning period and assess their impact on the growth and survival of Senegalese sole. Postlarvae were fed Artemia metanauplii with a peristaltic pump every hour for 12 hours per day or twice daily (morning and late afternoon). Both groups were suddenly weaned onto a commercial diet for an additional 30 days. At the end of the experiment, the relative growth rate and final dry weight were significantly higher and the survival significantly lower in the 12-hour treatment than in the twice-daily treatment. The feeding frequency had no effect on condition factor. The incidence of deformities was about 80% in both treatments.
- Co-feeding in Senegalese sole larvae with inert diet from mouth opening promotes growth at weaningPublication . Engrola, S.; Figueira, L.; Conceição, L. E. C.; Gavaia, Paulo J.; Ribeiro, Laura; Dinis, Maria TeresaThe aim of this study was to determine if sole larvae co-fed with inert diet at mouth opening would perform better than larvae fed with live prey and if such a feeding regime would produce better quality juveniles. The experiment was separated in to two phases: pelagic and benthic. In the pelagic phase, treatments consisted of the standard feeding regime (rotifer and Artemia feeding), the standard feeding regime and inert diet, and rotifer for a longer period than the standard feeding regime until larvae reached 9 days after hatching (DAH). By the end of the pelagic phase, when the postlarvae were 20 DAH, sole that were co-fed with inert diet from mouth opening, were significantly smaller in weight than postlarvae fed exclusively with live prey. Sole digestive maturation was improved by co-feeding the inert diet. Survival rates, skeletal deformities and quality evaluation were not affected by the feeding regimes. In the benthic phase, the postlarvae from standard feeding regime (pelagic phase) were separated in to two treatments: standard live Artemia metanauplii until weaning and standard frozen Artemia metanauplii until weaning. Remaining treatments were the follow up of treatments from the pelagic phase. At the end of the experiment i.e. 68 DAH, the postlarvae co-fed with inert diet from mouth opening were significantly larger than all the postlarvae from remaining feeding regimes. The results of the present study demonstrate that it is possible to offer inert diet to sole at mouth opening in a co-feeding regime and to produce better quality postlarvae. Co-fed sole were larger and had a better tail condition at the end of the weaning.
- Cloning, tissue and ontogenetic expression of the taurine transporter in the flatfish Senegalese sole (Solea senegalensis)Publication . Pinto, W.; Rønnestad, I.; Jordal, A. E. O.; Dinis, Maria Teresa; Aragão, C.Flatfish species seem to require dietary taurine for normal growth and development. Although dietary taurine supplementation has been recommended for flatfish, little is known about the mechanisms of taurine absorption in the digestive tract of flatfish throughout ontogeny. This study described the cloning and ontogenetic expression of the taurine transporter (TauT) in the flatfish Senegalese sole (Solea senegalensis). Results showed a high similarity between TauT in Senegalese sole and other vertebrates, but a change in TauT amino acid sequences indicates that taurine transport may differ between mammals and fish, reptiles or birds. Moreover, results showed that Senegalese sole metamorphosis is an important developmental trigger to promote taurine transport in larvae, especially in muscle tissues, which may be important for larval growth. Results also indicated that the capacity to uptake dietary taurine in the digestive tract is already established in larvae at the onset of metamorphosis. In Senegalese sole juveniles, TauT expression was highest in brain, heart and eye. These are organs where taurine is usually found in high concentrations and is believed to play important biological roles. In the digestive tract of juveniles, TauT was more expressed in stomach and hindgut, indicating that dietary taurine is quickly absorbed when digestion begins and taurine endogenously used for bile salt conjugation may be recycled at the posterior end of the digestive tract. Therefore, these results suggest an enterohepatic recycling pathway for taurine in Senegalese sole, a process that may be important for maintenance of the taurine body levels in flatfish species.