Total arsenic and inorganic arsenic content in Norwegian fish feed products

Samples of complete feedingstuffs for fish, and fishmeals from the Norwegian Fish Feed Monitoring Programme in 2003 were analysed for their total arsenic and inorganic arsenic contents. Microwave assisted wet digestion with nitric acid and hydrogen peroxide was used for the sample preparation for total arsenic analysis by ICPMS. Microwave assisted alkaline‐alcoholic dissolution of the sample was used for liberation of inorganic arsenic prior to analysis by anion‐exchange chromatography High Performance Liquid Chromatography Inductively Coupled Plasma Mass Spectrometry (HPLC–ICPMS). Concentrations in the ranges of 3.4–8.3 and 0.010–0.061 mg kg^?1 for complete feedingstuffs were found for total arsenic and inorganic arsenic, respectively. The results are in accordance with typical arsenic levels for fish reported in the literature and indicate that no transformation of chemical arsenic species occurs during the processing of complete feedingstuffs. Several of the complete feedingstuff samples had total arsenic concentrations above the EU maximum content of 6 mg kg^?1 in complete feedingstuffs for fish and complete feedingstuffs for fur animals. However, the species of toxicological relevance, i.e. inorganic arsenic, constitutes less than 1.2% of the total arsenic concentration in these samples. The data illustrate that fish feed with high levels of arsenic, but low levels of inorganic arsenic are at risk of being unnecessarily rejected from the fish feed market. Additionally, the results suggest that the maximum level for total arsenic in fish feed should be re‐evaluated and future maximum levels should be based on the chemical species of toxicological relevance, namely inorganic arsenic, rather than on total arsenic.     

Effect of water temperature on the feeding activity and the resultant mercury levels in the muscle of cultured bluefin tuna Thunnus orientalis (Temminck and Schlegel)

Tuna muscle often contains high levels of mercury, and fish samples with mercury concentrations ten times higher than the specified safety standards have been reported. Here, we report on the relationship between water temperature and the concentration of mercury in the tail muscle tissue of cultured bluefin tuna Thunnus orientalis. The fish used in this study were cultured at Fisheries Laboratory of Kinki University (Amami Experimental Station, Kagoshima, Japan). One hundred fish weighing 26.2–89.4 kg were selected for analysis between February 2007 and January 2008. Water temperature during rearing ranged from 21 to 29 °C. The total mercury levels were measured using the reduction vaporizing atomic absorption method after acid digestion. Body weight increased approximately 1.5 times that observed in a previous study, despite feeding activity either being the same or less than that observed previously. The average mercury concentration in white muscle was 0.353 mg kg^?1, remaining almost constant and independent of body growth. Unlike previous studies, seasonality was not observed in this study. Based on these findings, water temperatures within a certain range were considered to stabilize feeding activity and increase feeding efficiency. Consequently, water temperature is considered to have a moderating effect on seasonal fluctuations in muscle mercury concentrations in cultured bluefin tuna.     

Physiological effects of stocking density on the fish Piaractus mesopotamicus fed with red seaweed (Pyropia columbina) and β‐carotene‐supplemented diets

This study aimed at investigating the physiological responses of Piaractus mesopotamicus exposed to high stocking density and the potential protective role of supplemented diets. Fish were fed with basal, red seaweed (Pyropia columbina) or β‐carotene‐supplemented diets for 90 days. Then, fish were distributed at low (1.5 g/L) and high (22 g/L) stocking densities for 15 days. Fish exposed to the high density showed increased hepatosomatic index, haemoglobin content and mean corpuscular haemoglobin concentration (all diets); decreased haematocrit, mean corpuscular volume (basal and seaweed) and white blood cells count (all diets) were observed. High density‐exposed fish showed decreased plasmatic metabolites as well as the hepatic lipids content in basal and seaweed diets. Regarding oxidative stress, increased activity of glutathione S‐transferase in high density‐exposed fish muscle (all diets), and lower lipid peroxidation in liver (basal and β‐carotene) and intestine (basal and seaweed) were evidenced. Interactions between diet and stocking density were recorded regarding the triglycerides (decrease in fish exposed to high density fed with basal and seaweed) and hepatic lipids (decrease in fish exposed to high density fed with basal). The major changes occurred in haematologic and metabolic parameters as strategies to cope with overcrowding stress. Fish response to stocking density was not affected by diets.     

Effect of varying closes of organic and inorganic fertilizers on plankton production and fish biomass in brackish water fish ponds

The effects of four different doses of organic (cowdung) and inorganic fertilizers (single super phosphate: SSP) in combination were studied on plankton production, species diversity and fish biomass in saline and freshwater fish ponds. Physico-chemical factors of pond waters were also monitored. Alkalinity and nutrients increased with increase in the dose of fertilizers. Dissolved oxygen (DO) also remained sufficiently high up to the third treatment; however, levels declined significantly in the ponds receiving the fourth treatment (20 000 kg ha^-1 year^-1 of cowdung and 3000 kg ha^-1 year^-1 of SSP). The highest plankton population, species diversity and higher fish biomass was also observed in ponds which received the third dose of fertilizers (10 000 kg ha^-1 year^-1 of cowdung and 1500 kg ha^-1 year^-1 of SSP). However, a decline in these parameters was observed in ponds which received the highest (fourth treatment) dose of fertilizers. Nutrients remained slightly lower in brackish-water fish ponds. When species diversity values were compared, it was observed that, although values werte higher in freshwater ponds, their abundance (no. 1¹) remained lower than in brackish-water fish ponds. Similarly, fish biomass also remained significantly higher in brackish-water ponds than in freshwater ponds. From these studies, it can be concluded that a combination of 10 000 kg of cowdung + 1500 kg ha^-1 year^-1 of SSP appears to be the optimum dose.     

以大口黑鲈和大黄鱼配合饲料应用为例谈 改变鱼类营养和饲料研究范式

鱼类营养和饲料研究始于70年前并借鉴陆生动物营养研究经验形成了研究范式。在过去70年中,鱼类营养和饲料研究取得了大量的成果,这些研究成果推动了水产配合饲料技术的进步,为水产饲料产业从无到有、从小到大做出了贡献。然而,随着全球水产养殖规模的不断扩大,水产养殖发展面临的资源和环境压力日益增加,对水产饲料也提出了更高的要求。事实表明,根据一些鱼类营养和饲料研究成果所配方的饲料在养殖生产实践中往往不能取得预期的应用效果,这意味着在已有范式下取得的研究成果有时难以很好地满足现代鱼类养殖产业的需要。本文叙述了具有重要经济价值的两种肉食性鱼类大口黑鲈和大黄鱼配合饲料研发与应用的历程,指出对饲料蛋白需求的低估是限制配合饲料长期未能在大口黑鲈和大黄鱼养殖生产中应用的主要原因。早期研究报道大口黑鲈的饲料蛋白需求为400-440 g/kg,大黄鱼的饲料蛋白需求为450-470 g/kg。经过重新评估后将大口黑鲈和大黄鱼的最适饲料蛋白水平分别提高到480-510 g/kg和490-520 g/kg。在适宜的饲料蛋白水平下,投喂配合饲料的大口黑鲈和大黄鱼生长与投喂冰鲜鱼时相当。作者认为对饲料蛋白需求的低估与已有鱼类营养和饲料研究范式存在的不足有关,其表现为：（1）强调食物对鱼类生长的作用,但忽视了实验鱼遗传背景和食物以外的环境条件对生长和摄食的影响;（2）强调鱼类个体生长对评价营养需求和饲料质量的重要性,但忽视了鱼类个体生长差异并不能完全反映养殖产量和效益的事实;（3）强调生长和饲料利用效率作为鱼类营养和饲料研究评价指标的重要性,但忽视了养殖对环境和自然资源的负面影响是限制水产养殖产业可持续发展的瓶颈;（4）没有足够重视基础饲料配方在评价营养需求或饲料质量方面的影响,一些研究因基础饲料组成不当而产生没有实际意义的评价结果。针对上述问题,作者建议从概念、理论和研究方法方面对已有的范式做如下修改：（1）重视鱼类遗传背景和食物以外的环境条件对鱼类生长的影响,明确鱼类营养需求取决于其生长需求;（2）重视食物中各种营养素之间的相互作用,明确不同饲料原料在实现配方的营养平衡方面发挥着不同的作用;（3）重视对实验鱼种质和种群结构的选择,重视对照组和处理组个体生长差异的幅度对判断饲料处理效应的指示作用,重视饲料配方对渔业资源和环境等水产养殖可持续发展相关的内容的影响。经过修改后的研究范式更符合养殖生产实际,在此基础上开展研究所获得的成果也能够更好地指导配合饲料生产,为鱼类养殖产业的可持续发展提供更好的科技支撑。     

A low prevalence of mycobacteria in freshwater fish from water reservoirs, ponds and farms

A survey of the occurrence of mycobacteria was conducted from 717 freshwater fish (25 species) in two water reservoirs, five ponds and two farms in the Czech Republic. A total of 2182 tissue samples from these fish were examined using the conventional culture method. Thirteen mycobacterial isolates were obtained from 12 (1.7%) fish belonging to nine species. Isolates were identified using sequence analysis of the 16SrRNA gene as: Mycobacterium algericum, M. fortuitum, M. gordonae, M. insubricum, M. kumamotonense, M. nonchromogenicum, two isolates of M. peregrinum, M. terrae and M. triplex. Mycobacteria were isolated more frequently from fish skin and gills than from internal organs or muscles.     

Enhancement of growth and feed utilization of the European sea bass (Dicentrarchus labrax) fed supplementary dietary salt in freshwater

The effects of increased dietary sodium chloride supplement on growth, feed efficiency (FE), feed dispensed rate and fillet composition and morphological indices of European sea bass (initial weight of 4.9 g) were investigated in freshwater using five different levels of supplemental salt (0 (control diet, with no salt supplemented), 1%, 3%, 5% and 9% of diet). Over the experimental period of 50 days, the final weight of dietary salt (DS) groups was found to be approximately 19% higher than the control group. The final weight, specific growth rate and FE were greatest at the moderate level (1–5%) of salt supplementation. Optimum level of DS inclusion was calculated as 3%. Feed efficiency was significantly enhanced with increasing salt level up to 5%. A negative relationship between daily feed intake and FE (r²=0.66) was observed. The average muscle ratio (MR) in groups fed 1–5% supplemented salt was around 51.4% whereas fish receiving control and 9% salty diets had 5.3% lower MR (48.7%) (P<0.05). However, no significant effects of salt inclusion were found on viscera or hepatosomatic indices. Muscle ash and dry matter content slightly rose with increasing DS in the diet, but with no statistical difference (P>0.05). Similarly, no significant changes were observed in either muscle protein or lipid content among the groups (P>0.05).     

两种液化蛋白及其在饲料中的应用

IntroductionFish silage has been produced and used as high nutrition protein resource in feed for many years in Nor-way.The main raw materials are fish offals from fish processing industry,dead fish from fish farming factoryand pelagic fish.It is now a successful and profitable industry and benefits environment protection.With therapid growth in fish farming in China,the demands for high quality protein resource are increasing.There isgreat potential for adopting silage technology in China.A…     

Fat content in turbot feed: influence on feed intake, growth and body composition

The influences of dietary fat concentration on growth and energy deposition were studied in two replicated groups of turbot, Scophthalmus maximus (L.). Individually tagged turbot (202.3 g) held at 15.6 °C were offered dry pellets in excess. These contained either high-fat (25.4%) or low-fat (16.6%) concentration and identical protein (43.2%). After 3 months, feed treatments were crossed in two replicates, and the remaining fish were offered a mix of feeds for a further 2 months. Fish were sacrificed for analysis of body composition at the start of the experiment, at the time of feed treatment changes and when the experiment was terminated. There were no significant differences in energy intake, specific growth rate or weight between treatments at any time during the experiment. At the time of the feed treatment change fish offered high-fat feed had a significantly higher relative body fat (8.2 vs. 6.3% w/w) and lower body water (71.2 vs. 73%), but there were no differences in protein or ash content. By the end of the experiment, differences in body composition had diminished. The results indicate that fat content in the turbot may be manipulated by changing the dietary fat content, apparently without major influences on weight gain.     

Radiological risk assessment of fish feed and feed raw materials

In this study, natural radioactivity concentrations of fish feed and feed raw materials were assessed. Several feeds and raw materials were provided from the suppliers who dominate the aquaculture sector. ²²⁶Ra, ²³²Th and ⁴⁰K concentrations were determined by using a high‐purity germanium detector. The measured activity concentrations of samples ranged from 3.28 ± 0.27 to 15.90 ± 1.36, from 1.27 ± 0.10 to 12.07 ± 1.21 and from 52.01 ± 2.60 to 1,158.96 ± 54.42 Bq/kg for ²²⁶Ra, ²³²Th and ⁴⁰K respectively. The gamma dose rate and annual effective dose rate of samples were calculated to be in the range of 1.99–50.47 nGy/h and 2.44–61.89 µSv/yr respectively. Since the calculated radiological risk parameters of the samples were lower than the world wide average values, the radiation hazard is insignificant for human handlers.     

Aquatic food security: insights into challenges and solutions from an analysis of interactions between fisheries,aquaculture, food safety,human health,fish and human welfare,economy and environment

Fisheries and aquaculture production, imports, exports and equitability of distribution determine the supply of aquatic food to people. Aquatic food security is achieved when a food supply is sufficient, safe, sustainable, shockproof and sound: sufficient, to meet needs and preferences of people; safe, to provide nutritional benefit while posing minimal health risks; sustainable, to provide food now and for future generations; shock‐proof, to provide resilience to shocks in production systems and supply chains; and sound, to meet legal and ethical standards for welfare of animals, people and environment. Here, we present an integrated assessment of these elements of the aquatic food system in the United Kingdom, a system linked to dynamic global networks of producers, processors and markets. Our assessment addresses sufficiency of supply from aquaculture, fisheries and trade; safety of supply given biological, chemical and radiation hazards; social, economic and environmental sustainability of production systems and supply chains; system resilience to social, economic and environmental shocks; welfare of fish, people and environment; and the authenticity of food. Conventionally, these aspects of the food system are not assessed collectively, so information supporting our assessment is widely dispersed. Our assessment reveals trade‐offs and challenges in the food system that are easily overlooked in sectoral analyses of fisheries, aquaculture, health, medicine, human and fish welfare, safety and environment. We highlight potential benefits of an integrated, systematic and ongoing process to assess security of the aquatic food system and to predict impacts of social, economic and environmental change on food supply and demand.     

Generalist feeding strategies in Arctic freshwater fish: A mechanism for dealing with extreme environments

Generalist feeding strategies are favoured in stressful or variable environments where flexibility in ecological traits is beneficial. Species that feed across multiple habitat types and trophic levels may impart stability on food webs through the use of readily available, alternative energy pools. In lakes, generalist fish species may take advantage of spatially and temporally variable prey by consuming both benthic and pelagic prey to meet their energy demands. Using stomach content and stable isotope analyses, we examined the feeding habits of fish species in Alaska's Arctic Coastal Plain (ACP) lakes to determine the prevalence of generalist feeding strategies as a mechanism for persistence in extreme environments (e.g. low productivity, extreme cold and short growing season). Generalist and flexible feeding strategies were evident in five common fish species. Fish fed on benthic and pelagic (or nektonic) prey and across trophic levels. Three species were clearly omnivorous, feeding on fish and their shared invertebrate prey. Dietary differences based on stomach content analysis often exceeded 70%, and overlap in dietary niches based on shared isotopic space varied from zero to 40%. Metrics of community‐wide trophic structure varied with the number and identity of species involved and on the dietary overlap and niche size of individual fishes. Accumulation of energy from shared carbon sources by Arctic fishes creates redundancy in food webs, increasing likely resistance to perturbations or stochastic events. Therefore, the generalist and omnivorous feeding strategies employed by ACP fish may maintain energy flow and food web stability in extreme environments.     

Melano-macrophage centres and their role in fish pathology

Melano-macrophage centres, also known as macrophage aggregates, are distinctive groupings of pigment-containing cells within the tissues of heterothermic vertebrates. In fish they are normally located in the stroma of the haemopoietic tissue of the spleen and the kidney, although in amphibians and reptiles, and some fish, they are also found in the liver. They may also develop in association with chronic inflammatory lesions elsewhere in the body and during ovarian atresia. In higher teleosts, they often exist as complex discrete centres, containing lymphocytes and macrophages, and may be primitive analogues of the germinal centres of lymph nodes. Melano-macrophage centres usually contain a variety of pigments, including melanins, and these increase in range and volume in older fish or in the presence of cachectic disease. Melano-macrophage centres act as focal depositories for resistant intracellular bacteria, from which chronic infections may develop. Iron capture and storage in haemolytic diseases appears to be a primary function, but antigen trapping and presentation to lymphocytes, sequestration of products of cellular degradation and potentially toxic tissue materials, such as melanins, free radicals and catabolic breakdown products are among other functions that have been ascribed. Recent work suggests that they are a site of primary melanogenesis rather than mere storage. Melano-macrophage centres increase in size or frequency in conditions of environmental stress and have been suggested as reliable biomarkers for water quality in terms of both deoxygenation and iatragenic chemical pollution.     

汞及甲基汞在栉孔扇贝全组织内的积累与净化

以栉孔扇贝Chlamys farreri为研究对象,暴露于不同浓度HgCl2溶液35d后,转入自然海水中净化30d,检测不同时间点栉孔扇贝全组织中总汞与甲基汞含量,研究二者在栉孔扇贝组织中积累与净化情况.实验采用Kahle的双箱模型,数据处理采用两组不同动力学参数的双曲线毒性动力学模型.拟合发现,总汞和甲基汞在栉孔扇贝组织内的积累与净化规律符合双箱动力学模型;浓度低于2μg/L的汞溶液对栉孔扇贝的慢性毒性较小;各实验组暴露35d后栉孔扇贝组织中的总汞含量达到最高,暴露浓度与扇贝组织内的总汞积累量呈正比例关系.总汞在栉孔扇贝组织内的富集高峰出现在第35天,与理论点一致,而甲基汞富集高峰出现在40d后,有延迟现象;对比总汞和甲基汞在栉孔扇贝组织内的积累与净化动力学参数发现,总汞在栉孔扇贝组织内的积累因子（BCF）总体上大于甲基汞在栉孔扇贝组织内的BCF;汞与甲基汞在扇贝组织内的BCF和生物学半衰期（B1/2）与暴露液浓度均呈正相关关系;海水环境中总汞浓度低于0.064 8μg/L时,对栉孔扇贝的食品安全性无影响（以甲基汞为限量）.     

Possibility for decreasing of mercury content in bluefin tuna <Emphasis Type="Italic">Thunnus orientalis</Emphasis> by fish culture

ABSTRACT:   The bluefin tuna tested were reared for 22 months from eggs before the beginning of the experiment, and sampling was performed every 3 months over the following year. The experimental results showed that the mercury concentration in the muscle ranged from 0.32 to 0.85 μg/g, which is lower than that found in wild bluefin tuna of a similar size. Increase in the mercury concentration corresponding to the increase in body weight was not shown, and it was quite different with wild bluefin tuna. Furthermore, no significant relationship was found between the lipid concentration and the mercury concentration in muscle. Among the internal organs of cultured bluefin tuna, the heart (0.32–0.66 μg/g), liver (0.43–0.99 μg/g) and spleen (0.59–1.0 μg/g) contained higher concentrations of mercury. It was estimated that the full-cycle cultured bluefin tuna had been fed small fish containing lower concentrations of mercury, and that the mercury concentration of tuna would be almost equal throughout the year because the effect of mercury accumulation would be weakened by body growth. Therefore, it was concluded that selecting diet fish species might decrease mercury contents in cultured bluefin tuna.     

原子荧光法联测海洋生物中砷和汞方法的改进

本文运用微波消解,对原子荧光法联测海洋生物中砷和汞的方法进行改进,对仪器条件、微波消解体系、还原剂硼氢化钾浓度等条件进行优化,消除亚硝酸根（NO2）对测定的干扰。本方法经研究改进后,砷和汞的检测限分别为0．02mg／Kg和0．002mg／Kg;相对标准偏差分别为2．83％和2．05％;通过分析验证,改进后的方法简单、灵...     

Dietary lipid requirement of whiteleg shrimp Litopenaeus vannamei juveniles cultured in biofloc system

An eight‐week feeding trial was conducted to evaluate the contribution of biofloc on dietary lipid requirement in whiteleg shrimp Litopenaeus vannamei. Five diets with graded levels of dietary lipid (45, 60, 90, 120 and 150 g/kg) were fed to juvenile shrimp. Final weight, weight gain and specific growth rate of shrimp fed diets with 60, 90 and 120 g/kg lipid levels were significantly higher than those of shrimp fed diets with lipid levels 45 and 150 g/kg (p < .05). Feed efficiency and protein efficiency ratio of shrimp fed 60, 90 and 120 g/kg were higher than those fed 150 g/kg diet. Plasma total cholesterol and triglyceride levels were lower in shrimp fed 45 g/kg compared with those fed the 90 g/kg (p < .05). Also, lysozyme activity for 90 g/kg group was higher than the 15 g/kg group. Hepatopancreas lipase and amylase activities of shrimp fed 90 and 120 g/kg diets were significantly higher than those of shrimp fed 45 and 150 g/kg diets. Broken‐line regression analysis for weight gain indicated that the dietary lipid requirement of whiteleg shrimp juveniles reared in a biofloc system was estimated to be higher than 56 g/kg but <60 g/kg.     

Essential oil of Lippia grata (Verbenaceae) is effective in the control of monogenean infections in Colossoma macropomum gills,a large Serrasalmidae fish from Amazon

This study investigated the efficacy of Lippia grata essential oil (EO) against monogeneans of Colossoma macropomum and effects on the haematology after immersion baths. In the in vitro assays, the efficacy of 100, 250, 350 and 700 mg/L of L. grata EO and two controls were tested, of which one control was with the cultivation tank water and the other was with the tank water and 70% ethyl alcohol. Composition of majority bioactive compounds in the EO was carvacrol (48.12%), p‐cymene (24.39%) and γ‐terpinene (2.49%). Anacanthorus spathulatus, Notozothecium janauachensis, Mymarothecium boegeri and Linguadactyloides brinkmanni obtained of fish gills showed 100% immobilization in the in vitro assays when exposed to 700 and 350 mg/L after 30 min and 2 hr respectively. Fish showed tolerance to 700 mg/L of the EO, which was used in therapeutic in three consecutive baths, which caused lamellar hyperplasia in C. macropomum gills. The 700 mg/L of the EO in the therapeutic baths showed an efficacy of 95.1% against the monogeneans and caused decrease in haemoglobin, whereas control fish showed a reduction in mean corpuscular haemoglobin concentration. Results indicated that 700 mg/L of L. grata EO is a safe and effective concentration to treat C. macropomum infected with monogeneans.     

Control and utilization of inorganic nitrogen in intensive fish culture ponds

One of the main obstacles toward the intensification of aquaculture systems is the accumulation of inorganic nitrogen in the water, A solution demonstrated in this work is to control inorganic nitrogen levels through the induction of microbial protein synthesis. This is achieved by adding a carbonaceous substrate, adjusted in a way so as to supply the needed carbon to immobilize all the non-utilized nitrogen. Inorganic nitrogen levels are reduced due to the resulting production of microbial protein. The in situ produced microbial protein is a substitute to the protein added with the feed. Fish growth in the treated ponds was higher than the growth in conventionally fed ponds. Protein utilization was doubled due to the recycling of nitrogen in the pond system, leading to diminution of the deleterious inorganic nitrogen accumulation. The price of feed was reduced to 50-67% of that common in conventional ponds, due both to replacement of protein and limited wash-out of feed.