Optimal dietary protein levels in juvenile Senegalese sole (Solea senegalensis)

A study was undertaken to determine the dietary protein level for optimal growth performance and body composition of juvenile Senegalese sole. Five experimental extruded diets were formulated to contain increasing levels of protein [430, 480, 530, 570 and 600 g kg^?1 dry matter (DM)] and a constant lipid level, ranging from 100 to 130 g kg^?1 DM. Triplicate groups of 35 sole (initial body weight: 11.9 ± 0.5 g) were grown over 84 days in 60‐L tanks supplied with recirculated seawater. Fish were fed by means of automatic feeders in eight meals per day. At the start and end of the trial, whole‐body samples were withdrawn for proximate composition analysis. At the end of 84 days of experimental feeding, daily weight gain and specific growth rate in fish fed diets P43 and P48 were significantly lower than those found in fish fed higher protein level diets (P53, P57 and P59). Similarly, feed efficiency was also significantly lower in fish fed diet P43 than in fish fed all other dietary treatments. Sole juveniles fed lower protein level diets (P43 and P48) showed a significantly lower protein content than fish fed the higher dietary protein level treatments (P53, P57 and P60). Changes within the tested dietary protein levels did not affect significantly protein productive value or total nitrogen (N) losses in fish. However, daily N gain was significantly higher (P < 0.05) in fish fed diets P53 and P60 than in fish fed the lowest protein level diet (P43). Data from the present study indicate that diets for juvenile Senegalese sole should include at least 53% crude protein to maintain a good overall growth performance. Based on a second‐order polynomial regression model, the daily crude protein requirement for maximum whole‐body N gain as estimated here for Senegalese sole juveniles was 6.43 g kg^?1 body weight day^?1 which corresponds to a value of 1.03 g N intake kg^?1 body weight day^?1. If the present data are expressed on a dietary crude protein concentration basis, the allowance for maximum protein accretion (N gain) would be met by a diet containing a crude protein level of 600 g kg^?1.     

Occurrence of demersal fishes in relation to near‐bottom oxygen levels within the California Current large marine ecosystem

Various ocean‐climate models driven by increased greenhouse gases and higher temperatures predict a decline in oceanic dissolved oxygen (DO) as a result of greater stratification, reduced ventilation below the thermocline, and decreased solubility at higher temperatures. Since spreading of low oxygen waters is underway and predicted to increase, understanding impacts on higher trophic levels is essential. Within the California Current System, shoaling of the oxygen minimum zone (OMZ) is expected to produce complex changes. Onshore movement of the OMZ could lead to habitat compression for species with higher oxygen requirements while allowing expansion of species tolerant of low bottom DO. As part of annual groundfish surveys, we sampled catch across a range of conditions from the upper to the lower limit of the OMZ and shoreward across the continental shelf of the US west coast. DO ranged from 0.02 to 4.25 mL L^?1 with 642 stations (of 1020 sampled) experiencing hypoxic conditions in 2008–2010. Catch and species richness exhibited significant and positive relationships with near‐bottom oxygen concentration. The probability of occurrence was estimated for four species (spotted ratfish, petrale sole, greenstriped rockfish and Dover sole) using a binomial Generalized Additive Model. The models for each species included terms for position, day of the year, salinity, near‐bottom temperature and the interaction term between depth and near‐bottom DO. Spotted ratfish and petrale sole were sensitive to changes in near‐bottom oxygen, while greenstriped rockfish and Dover sole show no changes in probability of occurrence in relation to changes in oxygen concentration.     

Effects of raw corn starch levels on growth, feed utilization, plasma chemical indices and enzyme activities in juvenile yellowfin seabream Sparus latus Houttuyn

A 10‐week growth trial was conducted to evaluate the effect of raw corn starch levels on the growth, feed utilization, plasma chemical indices and metabolic enzyme activities of juvenile yellowfin seabream Sparus latus. Four semi‐purified experimental diets with different raw corn starch levels (5%, 10%, 20% and 26%) and a high‐protein control diet were prepared before the experiment and hand‐fed to triplicate groups of juvenile yellowfin seabream Sparus latus. Weight gain and specific growth rate for fish fed the diet containing 26% raw corn starch were significantly lower than those for fish fed 10% or 20% corn starch diets or the high‐protein control diet. Fish fed 10% or 20% corn starch diets had a slightly better growth performance than those fed the 5% corn starch diet. Feed efficiency ratio and protein efficiency ratio (PER) for 20% raw corn starch fed fish were the highest among all groups, although no statistically significant differences were found among the experimental groups. The high‐protein control group had a significantly lower PER value than other groups. Protein productive values for fish fed the 5% raw corn starch diet and the high‐protein control diet were significantly lower than those of fish fed the 20% raw corn starch diet, but not significantly different from the values of any other group. The values of intraperitoneal fat ratio, viscerosomatic index and condition factor, as well as body and muscle compositions, were unaffected by corn starch levels. The hepatosomatic index and liver glycogen level for fish fed 5%, 10%, 20% raw corn starch and the high‐protein control diets were equal but significantly lower compared with that of fish fed the 26% raw corn starch diet. Plasma values of the fish were not affected by various dietary treatments, except that a significantly higher plasma glucose concentration was measured in the high‐protein control group compared with the values in the other groups. There were variations in the activities of hepatic hexokinase and pyruvate kinase of the yellowfin seabream after they had been fed different dietary raw corn starch levels for 10 weeks. The overall results showed that a 20% inclusion level of raw corn starch in the diet was better utilized by juvenile yellowfin seabream than 5%, 10% or 26% levels and had a protein‐sparing effect.     

Culture of Senegal Sole Larvae without the Need for Rotifers

Two groups of Senegal sole (Solea senegalensis) larvae were cultured. One used rotifers for the first 10 days after hatching (dph) and enriched Artemia metanauplii from 6 to 30 dph and the other without rotifers, using enriched Artemia metanauplii as the sole food source. The quantity of metanauplii used was the same (group A), twice (group A2) and three times (group A3) the quantity of live prey (in dry weight) of the group fed with rotifers (group R). At the end of the experiment, the growth, in terms of total length and individual dry weight was significantly higher for the larvae on group A2 whilst rotifer fed larvae (R) showed the poorest results. Eye migration was also delayed by approximately 2 days in the group R. No significant differences were found in survival rates. The influence of diet on Senegal sole metamorphosis and its relationship with the size rather than the age of the fish are discussed.     

Comparing skeletal development of wild and hatchery-reared Senegalese sole (Solea senegalensis, Kaup 1858): evaluation in larval and postlarval stages

The 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.     

First results on spawning, larval rearing and growth of the wedge sole (Dicologoglossa cuneata) in captivity, a candidate species for aquaculture

The wedge sole is a target species in the fisheries of the Gulf of Cadiz (Spain). Having reared them to commercial size, we have studied reproduction and breeding in captivity of the wedge sole in this work here. The breeders adapt easily to captivity, and they can spawn in less than 1 year in captivity. The relative fecundity is relatively high, 1.06–2.33 · 10⁶ eggs kg⁻¹ per spawning season (mean 1.6 ± 0.1). Larval SGR is high, 7.2 ± 0.2% day⁻¹ (range 5.8–9.1), similar to other cultured flatfish species. In 1 year, some individuals reach market size and can release eggs, registering SGRs of 1.39–1.66% day⁻¹ (mean 1.56 ± 0.01). This species presents some very different characteristics with respect to other farmed flatfishes (turbot, halibut and Senegal sole, mainly), so that it is necessary to develop new techniques to optimise its cultivation. In the present work, the first results are presented on the biology of the wedge sole in captivity.     

Immune responses and gut morphology of Senegalese sole (Solea senegalensis,Kaup 1858) fed monospecies and multispecies probiotics

The current study aimed to determine the effects of dietary probiotic supplementation on growth, gut morphology and non‐specific immune parameters in Senegalese sole (Solea senegalensis) juveniles during a 1‐month trial. Fish were fed for 1‐month two diets with 1.0 or 4.6 × 10⁶ CFU kg^?1) of probiotic A (Bacillus sp., Pediococcus sp., Enterococcus sp. and Lactobacillus sp.) and two diets with 3.5 or 8.6 × 10⁵ CFU kg^?1 of probiotic B (Pediococcus acidilactici) and tested against an unsupplemented diet (control). Growth performance, as well as respiratory burst activity, nitric oxide (NO), alternative complement pathway (ACH50), lysozyme and peroxidase activities, was not affected by the dietary treatments. Probiotic supplementation tended to increased growth homogeneity between tanks having diet A₁ the best possible alternative to decrease costs associated to size grading. Villous length and number of goblet cells of the anterior intestine did not vary among treatments. Muscle duodenal layer was significantly thicker in fish fed probiotic A compared to probiotic B, when included at the lowest level (A₂ versus B₂). The current study indicate that the use of the multispecies probiotic at 1.0 × 10⁶ CFU kg^?1 might enhance protection against pathogen outbreak and increase nutrient absorption, whereas at the highest concentration could reduced size dispersion among tanks.     

草鱼养殖池塘生物膜固着微生物群落碳代谢Biolog分析

为了探索池塘生态系统中生物膜形成过程固着微生物对碳源的需求特征,以生态基为生物膜载体材料,以草鱼养殖池塘为生物膜培养环境,利用Biolog技术,分析了生物膜形成过程中(第0、15、30、45和60天)微生物群落碳代谢特征。结果表明,不同采样时间生物膜固着微生物样品平均颜色变化率(average well color development,AWCD)均在培养168 h后达到稳定,并且5个采样时间点的AWCD值即对单一碳源的利用能力存在显著差异,生物膜固着微生物的碳代谢能力在15、30、45 d时最强,显著高于0和60 d(P0.05);多样性指数也呈现出与AWCD值相同的规律,15、30和45 d生态基的4类多样性指数(Shannon指数、Pielou指数、Mc Intosh指数和丰富度指数)均显著高于0和60 d(P0.05);同一采样时间生物膜固着微生物对多聚物类和碳水化合物类的利用率明显高于胺类、氨基酸类、酚类和羧酸类;随着生物膜的形成,固着微生物提高了对α-D-葡萄糖-1-磷酸、L-丝氨酸、N-乙酰-D-葡萄糖氨、吐温40、D-甘露醇等碳源的利用率;生物膜微生物代谢特征PCA分析表明,主成分1(PC1)贡献度为33.9%,主成分2(PC2)贡献度为21.1%,15、30和45 d的固着微生物群落差异较小,碳源代谢差异不显著,而与0和60 d的碳代谢差异显著。池塘生态系统中生物膜固着微生物在15~45 d代谢能力最强,且对碳源的利用是有选择性的。     

Nutritional and culinary quality of bush bean populations intercropped with maize

Summary The intereropping of common bean (Phaseolus vulgaris L.) and maize (Zea mays L.) is a common practice in the Northwest of the Iberian Peninsula. In this experiment, 25 populations of bush bean were evaluated for nutritional and culinary traits of dry seed and immature pod in sole crop and in intercrop in two years and in two locations, in order to determine whether selection of bush bean in sole crop can result in genetic progress for intercrop.There were no differences in the population means between cropping systems. Significant differences were detected among populations for all traits tudied except starch content, crude ash, water absorption and coat proportion. Population x environment interaction was significant for pod thickness. Bean populations did not interact with cropping systems for any trait, although there were differences between cropping systems for crude protein. These results suggest that a sole crop system provides sufficient information to select bean populations efficiently for the bush bean-maize intercropping system, although the advanced generations of the breeding program should be tested for quantitative traits such as protein content in the appropriate cropping system (intercropping) to know the competitive ability with the associated species. This would permit to choose bush bean populations which complement more efficiently and would be less competitive with the maize population.