Self-feeding activity patterns in gilthead sea bream (Sparus aurata), red porgy (Pagrus pagrus) and their reciprocal hybrids

This study was conducted to monitor feeding activity of gilthead sea bream (Sa) and red porgy (Pp) and to investigate the hereditary effects on feeding in their hybrids (female Sa×male Pp, female Pp×male Sa), obtained after artificial crosses. All fish groups were held in 500-l tanks under ambient temperature (15–25°C) and light conditions (daylength from 9 h 30 min to 14 h 48 min). Fish (initial body weight 100–165 g) were fed by means of self-feeders, which were connected to a computer, recording fish feeding activity for a year. Results showed that there was a 24-h periodicity in all fish types over the experiment. In their daily feeding patterns, both parental species were diurnal: red porgies had a stable daily pattern over the experiment, while gilthead sea bream shifted their activity from a general daylight fluctuation in warm periods to an afternoon peak in cold periods. The Sa×Pp hybrids showed intermediate feeding patterns compared to their parents in warm periods and a pattern that was similar to the red porgy in cold periods, while the Pp×Sa hybrids had rather unchangeable daily feeding patterns, which were not related to the parental ones. The proportion of night feed demands increased in cold periods independent of fish group. The relationship between temperature and feed intake was species-dependent. Finally, this study indicated that feeding expression in hybrids was related to the combination of the parental genome, supporting our hypothesis for a hereditary influence on feeding activity in fish.     

饲料中添加纤维素酶对团头鲂生长的影响

在 A、B、C、C0 和 D五组团头鲂鱼种 (体均重 2 .35± 0 .2 0 g)的配合饲料中分别加 0、6 0 0、2 4 0 0、2 4 0 0和 4 2 0 0 U/ kg纤维素酶。其中 B、C、D组中加入的纤维素酶都经过适当的预处理 ,而 C0 组饲料则直接添加 2 4 0 0 U/ kg的纤维素酶。经 56天喂养试验 ,结果显示 :投喂 B、C两组饲料的鱼体增重率分别比 A组提高了 14 .59%和 34.18% ,饲料效率也分别提高 6 .0 6 %和13.6 4 % ;而 C0 和 D组的生长性能则与 A组之间没有显著性差异。     

Control of dissolved oxygen levels of water in net pens for fish farming by a microscopic bubble generating system

ABSTRACT:   A microscopic bubble generating system (MBGS) has been developed to control dissolved oxygen (DO) levels suitable for fish farming. The MBGS has been tested to confirm its capability in net pens. Water conditions in a fish farm were monitored every two hours from June to October 2004 by setting an online vertical profiling system (OVPS) close to the net pen. DO in the net pen water decreased to physiologically stressful levels for the fish during the night (4.84–5.51 mg/L), while the DO was kept in saturated conditions during the day, due to oxygen supply from phytoplankton. The MBGS was operated from the evening to the morning of the next day for 16 h, to successfully create DO-saturated conditions in the net pen water at night. By using microscopic bubbles during the warm seasons, DO levels in the net pen water could be improved to a level suitable for fish farming. However, the low DO levels (<5.0 mg/L) of the bottom water occasionally extended to the net pen layers, despite the supply of microscopic bubbles to the water. To maintain the DO of the net pen water at levels suitable for fish farming, DO supply to the net pen water and the bottom water needs to be increased, and the organically enriched sediment just below the net pens needs to be treated.     

Evaluation of corn gluten meal as a protein source in diets for gilthead sea bream (Sparus aurata L.) juveniles

A 12‐week growth trial was conducted to evaluate corn gluten meal as an alternative protein source to fish meal in diets for gilthead sea bream juveniles. The experimental diets were formulated to be isonitrogenous and isoenergetic and to have 20%, 40%, 60% and 80% of fish meal protein, the only protein source in the control diet, replaced by corn gluten meal. At the end of the growth trial only the group fed the diet with 80% corn gluten protein exhibited significantly reduced growth and feed efficiency compared with the fish meal‐based diet. This was most likely due to a dietary amino acid deficiency in that diet. A trend was noticed for feed efficiency to improve with the replacement of fish meal protein in the diets up to 60%. There were no significant differences among groups in protein and energy retention (as percentage of intake). At the end of the trial whole body water content of the experimental groups was significantly lower and the lipid content of groups including 60% and 80% corn gluten protein was significantly higher than that in the control. No other differences were observed in whole body composition among groups. Apparent digestibility coefficients (ADC) of the diets were evaluated in a separate trial. The ADC of dry matter of the experimental diets was significantly higher than in the control diet; there were no significant differences among diets in the ADC of energy and protein, except for the ADC of protein of diet with 80% corn gluten protein, which was significantly lower than the control. The results of this study indicate that corn gluten meal can replace up to 60% fish meal protein in diets for gilthead sea bream juveniles with no negative effects on fish performance.     

真鲷虹彩病毒引起养殖斑石鲷大规模死亡的研究

2017年8月,山东省烟台市某养殖场网箱养殖的斑石鲷(Oplegnathus punctatus)幼鱼突然发病并大量急性死亡。疾病调查显示,养殖海域水温为26℃~28℃;病鱼为4~5月龄,全长为(16.3± 1.6) cm,体重为(156.9±37.0) g;80万尾斑石鲷幼鱼2周内累积死亡率达90%以上,经济损失惨重。临诊检查发现,病鱼体表无明显损伤,但活力差、呼吸急促。剖检可见病鱼脾肿大、质地脆、易碎,肾糜烂,肝有出血点。组织切片观察发现,病鱼脾、肾造血组织中可见许多直径约为20 μm的肿大细胞,肿大细胞内含有大量直径约为145 nm、呈六边形的病毒颗粒。用过滤除菌的病鱼脾组织匀浆液,腹腔注射感染健康斑石鲷,感染组14 d内累积死亡率达95%。人工感染病鱼表现出与自然发病鱼类似的外观症状,且在脾、肾组织切片中也可观察到大量的肿大细胞及相似的病毒粒子。使用特异性PCR引物,从自然发病鱼和人工感染病鱼的肝、脾和肾组织中均检测到鱼类虹彩病毒的高强度感染。克隆、测序得到了1362 bp的病毒主要衣壳蛋白基因(MCP),序列比对显示,该病毒的MCP序列与真鲷虹彩病毒(RSIV) RIE12-1的相应序列完全相同。构建的虹彩病毒系统发育树也显示,该病毒属于虹彩病毒科肿大细胞病毒属RSIV类群,是RSIV的一个分离株。本研究首次证实RSIV可以导致斑石鲷大规模死亡,研究结果为诊断和防治斑石鲷病毒病提供了重要参考。     

淡水黑鲷染色体核型分析

以淡水黑鲷(Hephaestus fuliginosus)头肾组织为材料,采用腹腔注射植物血细胞凝集素(PHA)、秋水仙素和空气干燥法制备染色体标本,进行染色体核型分析。结果显示,淡水黑鲷染色体为48条,核型公式为2n=48=4m+44t,NF=52;未发现随体、次级缢痕及异形性染色体;其核型符合典型的高位类群鱼类核型特征。     

Natural abundance of 15N and 13C in fish tissues and the use of stable isotopes as dietary protein tracers in rainbow trout and gilthead sea bream

For developing efficient diets, two sets of experiments examined whether the use and allocation of dietary protein can be traced by labelling with stable isotopes (¹⁵N and ¹³C) in two culture fish ( Oncorhynchus mykiss and Sparus aurata) . In the first experiment, natural abundance and tissue distribution of these isotopes were determined, by measuring the δ¹³C and δ¹⁵N values by isotopic ratio mass spectrometry, in fingerlings (14–17 g) adapted to diets differing in the percentage of fish meal replacement by plant protein sources. For both species, δ¹⁵N and δ¹³C were greater in tissues with higher protein and lower lipid content. Delta ¹⁵N of diets and tissues decreased as replacement increased, suggesting δ¹⁵N can be used as a marker for dietary protein origin. The ¹⁵N fractionation (δ¹⁵N fish − δ¹⁵N diet) differed between groups, and could thus be used to indicate protein catabolism. In the second experiment, fish (75–90 g) of each species ingested a diet enriched with ¹⁵N-protein (10 g kg⁻¹ diet) and ¹³C-protein (30 g kg⁻¹ diet). These proportions were suitable for determining that the delta values of tissue components were high enough above natural levels to allow protein allocation to be traced at 11 and 24 h after feeding, and revealed clear metabolic differences between species.     

Purification and characterization of phospholipase A2 from the pyloric caeca of red sea bream, Pagrus major

A phospholipase A₂ was purified 55,000-fold in a yield of 10% from the lipid-free extract of powder of the pyloric caeca of red sea bream to near homogeneity by sequential column chromatography on S-sepharose fast flow, butyl-cellulofine, Asahipak ES-502C cation-exchange HPLC, TSK gel G3000SW gel-filtration HPLC, and Asahipak ODP-50 reversed-phase HPLC. The final preparation showed a single band with the apparent molecular mass of 14 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis, and an estimated specific activity was 717 µmol min^-1 mg^-1 protein. The purified enzyme had a pH optimum in the range of pH 8.0–9.0 and required the presence of both 8 mM of Ca²⁺ and from 2 to 10 mM of sodium deoxycholate for its maximal activity, using 2 mM of phosphatidylcholine as a substrate. The purified enzyme preferentially hydrolyzed the 2-acyl ester bonds of both phosphatidylglycerol and phosphatidylcholine in the presence of sodium deoxycholate, followed in order by phosphatidylethanolamine and phosphatidyl-serine. In contrast to porcine pancreatic PLA₂, pyloric caeca PLA₂ hydrolyzed mixed-micellar phosphatidylcholine substrate effectively, regardless of the kinds of bile salts used. These results indicate that Ca²⁺-dependent low molecular mass PLA₂, so called secretory PLA₂, occurs in the pyloric caeca of red sea beam.     

Nutrient digestibility profile of premium (category III grade) animal protein by-products for temperate marine fish species (European sea bass, gilthead sea bream and turbot)

Three trials, with classical experimental designs for in vivo digestibility studies, were conducted to determine the apparent digestibility coefficient (ADC) of protein (ADCp), lipid (ADCl), energy (ADCe) and amino acids (AA) in selected animal by-products fed to European sea bass, Dicentrarchus labrax (Trial 1), gilthead sea bream, Sparus aurata (Trial 2), and turbot, Psetta maxima (Trial 3). In each trial, five experimental diets [including a reference diet (RD)] where fish meal (FM) was used as the sole protein source were fed ad libitum to the fish for a period of 4 weeks. Test diets were based on the FM RD and obtained by replacing 30% of the RD with a category III designated European animal by-products (fit for human consumption), namely: steam hydrolysed feather meal (HFM), enzyme-treated feather meal (EFM), poultry meat meal (PMM) and spray-dried haemoglobin meal (SDHM). Faecal material was collected using the 'Guelph system', and nutrient and energy digestibility coefficients were related to the measurement of chromic oxide (Cr₂O₃) incorporated into the diet at a rate of 0.5%. Without any exception, FM diets yielded the best digestibility values for all macro-nutrients and by all fish. Among the test ingredients, ADCp was consistently higher for PMM and SDHM in the three species (85.5%, 91.1% in sea bass; 79.2%, 82.8% in sea bream; and 78.4%, 74.8% in turbot). Conversely, ADCp of HFM and EFM were less efficiently digested (67.2%, 68.2% in sea bass; 21.5%, 21.7% in sea bream; and 46.6%, 36.0% in turbot). However, the novel processing method applied to feather meal did not considerably influence the digestibility of most of the nutrients in this feedstuff. The current investigation yielded valuable numerical ADC for EAA considered to be of prime importance in generating balanced diet formulations.     

几种淡水商品鱼背、腹肉一般成分的季节变化

本文研究了鲢、鳙、草鱼、团头鲂、鲫背、腹肉蛋白质、脂肪等的季节变化及其有关营养、风味特点，发现5种鱼背肉脂肪含量12个月平均值均低于1％；蛋白质含量平均值在17．3—18．5％之间．不存在季节变化；是一种典型的高蛋白、低脂肪食物。反之，腹肉脂肪含量在2．2—9．7％之间．具有较多的脂肪和较好的风味。针对这种特点．鲢、鳙、草鱼等大型鱼采取背部、腹部分别加工是可取的。此外还测定证实鲢肌肉中含有较多的EPA和DHA。