黑龙江勤得利湾鱼类区系组成特征

初步调查勤得利湾鱼类共计58种，隶属于15科，其中鲤科鱼类为最多，43种，占水系鱼类总数74．13％；鳅科5种，占0．09％；偿科、鲶科各2种，各占0．035％；鲟科、狗鱼科、鳕科、鮨科、塘鳢科、鳢科、杜父鱼科各1种，共占0．017％。肉食性鱼类种类相对较多。通过比较分析，黑龙江勤得利湾鱼类组成与黑龙江中游表现出很大的相似性。     

Effects of docosahexaenoic, eicosapentaenoic, and arachidonic acids on the early growth, survival, lipid composition and pigmentation of yellowtail flounder (Limanda ferruginea): a live food enrichment experiment

The role of dietary ratios of docosahexaenoic acid (DHA, 22:6n−3), eicosapentaenoic acid (EPA, 20:5n−3) and arachidonic acid (AA, 20:4n−6) on early growth, survival, lipid composition, and pigmentation of yellowtail flounder was studied. Rotifers were enriched with lipid emulsions containing high DHA (43.3% of total fatty acids), DHA+EPA (37.4% and 14.2%, respectively), DHA+AA (36.0% and 8.9%), or a control emulsion containing only olive oil (no DHA, EPA, or AA). Larvae were fed differently enriched rotifers for 4 weeks post-hatch. At week 4, yellowtail larvae fed the high DHA diet were significantly larger (9.7±0.2 mm, P<0.05) and had higher survival (22.1±0.4%), while larvae fed the control diet were significantly smaller (7.3±0.2 mm, P<0.05) and showed lower survival (5.2±1.9%). Larval lipid class and fatty acid profiles differed significantly among treatments with larvae fed high polyunsaturated fatty acid (PUFA) diets having higher relative amounts of triacylglycerols (18–21% of total lipid) than larvae in the control diet (11%). Larval fatty acids reflected dietary levels of DHA, EPA and AA while larvae fed the control diet had reduced amounts of monounsaturated fatty acids (MUFA) and increased levels of PUFA relative to dietary levels. A strong relationship was observed between the DHA/EPA ratio in the diet and larval size (r²=0.75, P=0.005) and survival (r²=0.86, P=0.001). Following metamorphosis, the incidence of malpigmentation was higher in the DHA+AA diet (92%) than in all other treatments (50%). Results suggest that yellowtail larvae require a high level of dietary DHA for maximal growth and survival while diets containing elevated AA exert negative effects on larval pigmentation.     

渤海鱼类群落结构及其主要增殖放流鱼类的资源量变化

基于2010年5月和8月渤海渔业调查数据,结合1959年以来渤海鱼类相关文献资料,对渤海鱼类群落结构的演替、主要增殖放流鱼类的资源动态作了初步分析.结果表明,渤海鱼类群落优势种由个体大、营养层次高的带鱼Trichiurus haumela、半滑舌鳎Cynoglossus semilaevis等优质底层鱼类逐渐被黄鲫Setipinna taty、鳀Engra ulis ja ponicus等个体小、营养层次低的小型中上层鱼类所替代,并且除黄鲫外,其他小型鱼类优势种也在不断更替中.另外,生物健康度指数(BHI)分析显示,渤海鱼类群落处于相对不稳定状态.鱼类资源量急剧降低,尤其在5月,CPUE由1959年的186 kg/h下降至目前不足1 kg/h,鱼类资源密集区主要分布在莱州湾、渤海湾和渤海中部,而辽东湾分布相对较少,并且鱼类资源与海蜇呈交错分布.近年来,渤海增殖放流的鱼类仅有花鲈Lateolabrax japonicus和许氏平鲉Sebastes schlegeli的资源量有小幅度回升,其他种类从20世纪80年代开始资源量一直处于下降趋势.从渤海鱼类群落结构的演替和增殖放流鱼类的资源量变化来看,渤海鱼类群落依旧是小型经济价值较低的种类控制其能流结构.除花鲈外,其他增殖放流鱼类的资源量均不足历史最高资源量的1％,其资源量的恢复尚有很大的空间,增殖潜力很大.     

Production of Interesting Peptide Fractions by Enzymatic Hydrolysis of Tuna Dark Muscle By-Product Using Alcalase

ABSTRACT

A protein hydrolysate was prepared from proteins of tuna dark muscle by-product. The hydrolysis conditions (time, temperature, pH, and enzyme concentration) using Alcalase was optimized by response surface methodology (RSM). The regression coefficient close to 1.0, observed during experimental and validation runs, indicated the validity of the model. The hydrolysate produced under the optimum conditions determined by RSM has a low rate of peptide fraction of molecular weight of 4–1 kDa. Meanwhile, the results obtained by hydrolysis under optimal conditions determined by a complementary study (temperature 55°C, time 60 min, 1% enzyme concentration, and pH 8.5) show that the hydrolysate produced has a height rate of the peptide fraction of molecular weight of 4–1 kDa. The amino acid composition of the protein hydrolysate prepared proved to have the potential for application as an ingredient in balanced fish diets and as a source of nitrogen in microbial growth media.     

Tuna viscera protein hydrolysate: nutritive and disease resistance properties for Persian sturgeon (Acipenser persicus L.) larvae

The effect of fish protein hydrolysate (FPH) on the growth, feed utilization, digestive enzymes, gut microflora and resistance to bacterial challenge in Persian sturgeon (Acipenser persicus) larvae during a 45‐day feeding trial has been investigated. Artificial diets containing different levels of tuna visceral protein hydrolysate (PH0, PH10, PH25 and PH50) and live foods (Artemia: 5 days, Daphnia: 40 days) were fed to Persian sturgeon larvae. Larvae fed on the PH10 and PH25 had growth, feed utilization, protein content and trypsin activity significantly better than PH0 and PH50 groups (P < 0.05). Condition factors, survival rate and pepsin activity were not significantly different (P > 0.05). Brush border membrane enzymes to cytosolic enzyme ratio revealed that maturation had been occurred in 41 days post hatch (dph) at moderate FPH levels. In 54 dph larvae, this ratio was not affected by the level of FPH in the diet. No significant differences were observed in the total number of gut microflora or in the resistance to Aeromonas hydrophila (P > 0.05), whereas lactic acid bacteria was significantly higher in PH50 (P < 0.05). The results of this study show that application of moderate levels of FPH in Persian sturgeon diets could enhance larvae performance due to the early maturation in intestinal.     

Growth and production of the Amazonian tambaqui in fixed cages under different feeding regimes

Experimental culture of the native Amazonian fish tambaqui, Colossoma macropomum, in fixed cages was carried out over a period of 8 months, in Lake Urubu (Rio Grande do Norte, Brazil), to assess the viability of fixed cage culture of tambaqui and to test the influence of diet on growth rates. Nine synthetic net cages (1 m³) were each stocked with 45-day-old fish (mean weight 3 g; mean total body length 51 mm) at a density of 34 fry m^–3. During the first 2 months of culture, fish were fed a balanced formulated feed on an as-fed basis at the rate of 5% body weight day^–1. During months 3–8 this continued for fish in treatment 1 while those in treatment 2 were fed tropical regional fruits, on a wet weight basis at the rate of 5% body wt day^–1. Fish in treatment 3 were given no supplementary feed. Monthly biometric measurements were made on all fish. Fixed cage fish culture was shown to be a viable and simple technique. Survival in all treatments was 100%. With balanced supplementary feed, production was 14.4 kg m^–3, compared with 4.9 kg m^–3 and 2.1 kg m^–3, respectively, in the treatments where fish were fed with fruits and were not given any supplementary feed.     

Effect of dietary protein/carbohydrate ratio on activities of hepatic enzymes involved in the amino acid metabolism of Nile tilapia, Oreochromis niloticus (L.)

This study investigated the influence of different dietary protein/carbohydrate ratios on activities of enzymes involved in the amino acid metabolism as well as on growth performance and body composition of Nile tilapia (Oreo- chromis niloticus). Fish were fed semi-synthetic diets differing in their protein/carbohydrate ratio. The diets were formulated to be isolipidic and isoenergetic (on the basis of metabolizable energy). Fish were reared individually. After a prefeeding phase, tilapia were randomly assigned to three groups and were fed the experimental diets at a relatively low level. The study lasted 9 weeks. Proximate composition, gross energy content, and activities of aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT) in the liver of fish were determined. While the mean growth rate and feed conversion efficiency did not differ significantly among the feeding groups, the body composition showed significant differences. The dietary protein/carbohydrate ratio had no significant effect on the protein and energy gain, but the lipid gain was significantly higher in tilapia fed the low-protein diet. The activities of ASAT and ALAT per gram of liver and per gram of soluble protein were significantly increased in fish fed the high-protein diet. There was a significant positive correlation between the activities of ASAT and ALAT. The activities of both enzymes in the liver were significantly higher in fish with a higher protein gain. Measuring the activities of enzymes involved in the amino acid metabolism can provide more information about the metabolic utilized dietary protein.     

福建三沙湾鱼类群落组成特征及其多样性

根据2008年福建海区三沙湾春季和秋季两个季度月鱼类调查资料,分析和研究福建三沙湾鱼类群落结构及生态类型特点。结果表明:渔获鱼类经鉴定共有94种,其中,软骨鱼类的须鲨目、鲼形目和电鳐目各1种;硬骨鱼类的鲈形目最多,47种,其次鲱形目10种,鲽形目9种。以暖水性种类为主,占总种数70.2%,具有明显的热带和亚热带特征。从种类重量和数量组成看,整个调查港湾以具有一定经济价值种类为主,优势种为半滑舌鳎(Cynoglossus sem ilaevis)、硬头鲻(Mugil strongylocephalus)、棘头梅童鱼(Collichthys lucidus)、红狼牙虾虎鱼(Odontam blyopus rubicundus)、大黄鱼(Larim ichthys crocea)、孔虾虎鱼(Trypauchen vagina)、龙头鱼(Harpodon neherus)、棱鮻(Liza carinatus)、海鳗(Muraenesox cinereus)等;总平均资源相对密度为3.49 kg/h,种类多样性指数H为2.017,种类均匀度指数J′为0.820,种类丰富度指数D为2.434。整个海区优势种明显,平均资源相对密度低,多样性指数和均匀度指数分布处于中下水平。     

Shrimp and fish pond soils: processes and management

The pond bottom soil and the accumulated sediments are integral parts of ponds. Concentrations of nutrients, organic matter and microorganism density in the pond bottom are several orders of magnitude greater than in the water. The accumulation of organic sediments may limit pond intensification. The intensive organic matter degradation at the pond bottom and high sediment oxygen demand exceeds the oxygen renewal rate. This leads to the development of anoxic conditions in the sediments and at the sediment–water interface. A series of anaerobic processes, affected by the redox potential of the system, are taking place. A large number of potentially toxic materials are generated. Among those are organic acids, reduced organic sulfur compounds, reduced manganese and sulfides.

Shrimp, as animals that normally live on or near the bottom, are exposed to conditions on the pond bottom. Exposure to toxic materials endanger the well being of the cultured shrimp. Reduced feeding, slower growth, mortality and possibly higher sensitivity to disease are reported.

The rational use of aerators to minimize the area of sludge accumulation, construction of ponds to trap sludge, stirring sediments, chemical poising of the redox system and environmentally accepted treatment and reuse of drained sediments are means to control the conditions at the pond bottom.     

Regulation of growth, fatty acid composition and delta 6 desaturase expression by dietary lipids in gilthead seabream larvae (Sparus aurata)

The Δ6 and Δ5 desaturases and elongases show only very limited activity in marine fish, and little is known of the possibility of enhancing Δ6 desaturase gene expression in these fish. The use of plant oils in marine fish diets is limited by their lack of n−3 highly unsaturated fatty acids (HUFA) despite an abundant content of the 18C fatty acid precursor linoleic and α-linolenic acids. The objective of the present study was to determine the ability of larval gilthead seabream to utilize vegetable oils and assess the nutritional regulation of Δ6 desaturase gene expression. Seventeen-day-old gilthead seabream larvae were fed during a 17-day period with one of four different microdiets formulated with either sardine fish oil (FO), soybean, rapeseed or linseed oils, respectively, or a fifth diet containing defatted squid meal and linseed oil. Good larval survival and growth, both in terms of total length and body weight, were obtained by feeding the larvae either rapeseed, soybean or linseed oils. The presence of vegetable oils in the diet increased the levels of 20:2n−9 and 20:2n−6, 18:2n−9, 18:3n−6, 20:3n−6 and 20:4n−6, in larvae fed rapeseed and soybean oils in comparison to those fed FO. In addition, a sixfold increase in the relative expression of Δ6 desaturase-like gene was found in larvae fed rapeseed and soybean oils, denoting the nutritional regulation of desaturase activity through its gene expression in this fish species. However, feeding linseed oil did not increase the expression of the Δ6 desaturase gene to such a high extent.