BIODIVERSITY AND CONSERVATION OF FRESHWATER FISH IN HONG KONG, CHINA

We surveyed the distribution, composition and diversity of freshwater fish in Hong Kong, China from 2002 to 2004. Sites surveyed were mainly streams, marshes and estuaries. There are ponds for aquaculture and reservoirs in Hong Kong but no large natural water bodies. From the 220 sites surveyed, 114 species of 37 families were found. Gobiidae (with 24 species) and Cyprinidae (21 species) were the dominant families. This survey has increased the number of freshwater fish species recorded in Hong Kong to 167. Among these, 71 (42.5%) are primary freshwater fish, 44 are brackish and 46 are vagrants. The remaining 6 species are diadromous. In Hong Kong, freshwater fish are conserved by a combination of measures. About 38% of Hong Kong’s land area is designated as country parks and/or special areas, and is managed for nature conservation and educational purposes. In addition, another 5% of land area is zoned for conservation in the statutory land use zoning system to protect them from development and incompatible land uses. Major development projects have to go through the statutory environmental impact assessment process to ensure that they will not have adverse impact as far as practicable. There are conservation action plans for important species. For example, captive-bred individuals of the endemic Hong Kong Paradise Fish Macropodus hongkongensis have been released to suitable and secure sites inside country parks and their populations are regularly monitored. Other measures such as wetland creation, restoration and enhancement programmes are also implemented for freshwater fish conservation.

Bioaccumulation and depuration of chromium in the selected organs and whole body tissues of freshwater fish Cirrhinus mrigala individually and in binary solutions with nickel

Contamination of aquatic ecosystems with heavy metals has been receiving increased worldwide attention due to their harmful effects on human health and other organisms in the environment. Most of the studies dealing with toxic effects of metals deal with single metal species, while the aquatic organisms are typically exposed to mixtures of metals. Hence, in order to provide data supporting the usefulness of freshwater fish as indicators of heavy metal pollution, it has been proposed in the present study to investigate the bioaccumulation and depuration of chromium in the selected organs of freshwater fingerlings Cirrhinus mrigala, individually and in binary solutions with nickel. The results show that the kidney is a target organ for chromium accumulation, which implies that it is also the ＂critical＂ organ for toxic symptoms. The results further show that accumulation of nickel in all the tissues of C. mrigala is higher than that of chromium. In addition, the metal accumulations of the binary mixtures of chromium and nickel are substantially higher than those of the individual metals, indicating synergistic interactions between the two metals. Theoretically the simplest explanation for an additive joint action of toxicants in a mixture is that they act in a qualitatively similar way. The observed data suggest that C. mrigala could be suitable monitoring organisms to study the bioavailability of water-bound metals in freshwater habitats.

Length-weight relationships for six freshwater fish species in Iran

The aim of this study is to report the length-weight relationship parameters （a and b） for some economically important fish species from Iranian freshwaters. The length-weight relationships （LWR） are calculated for six freshwater fish species collected during 2006 and 2007 in Iran. The values of the exponent b in the LWR （W=aL^b） vary between 2.985 and 3.543. The LWR with high correlation coefficient （r^2） is significant for all the species. These parameters axe of great importance to evaluate the relative condition of populations, biology, species management and their fisheries and stock assessment. The application of the length-weight relationships presented here should be limited to the observed length ranges.

Development of Intermediate Foodstuff Derived from Freshwater Fish in China

According to the three-dimensional contour maps showing the gel-forming properties of surimi derived from freshwater fish, 8 species of surimi were classified into two types. The-valley type surimi （silver carp, big-head carp, Chinese snake head and blunt snout bream） shows easy setting, low resistance to gel collapse, high enhancement ability with two-step heating, and narrow optimum heating temperature and time area, which are of the same characteristics as the walleye pollack surimi. In contrast, the Plateau type surimi （tilapia, grass carp, mud carp and common carp） exhibits difficult setting, high resistance to gel collapse, no enhancement ability with two-step heating, and wide optimum heating temperature and time area. There are seasonal changes of gelling properties of silver carp surimi, and the setting ability of surimi gel is higher in winter and lower in summer. The marine fish meat gels and the freshwater fish meat gels have the same acceptability for inland Chinese according to the sensory evaluation results. A slight increase in sensory scorings of kamaboko gels occurred when the extract from walleye pollack muscle was added, especially in the odor scoring of silver carp kamaboko gels.

Microbial Load (Bacteria, Coliform and Mould Count/Flora) of Some Common Hot Smoked Freshwater Fish Species Using Different Packaging Materials

Three different packaging materials of (37 cm × 25 cm) size (Sealed Transparent Polythene Bag (STPB) Sealed Paper Bag (SPB) (Brown envelope), Open Mouth Polythene Bag (OMPB) (Black incolour)) were used for Oreochromisniloticus (O), Clariasgariepinus (C) and Mormyrusrume (M). Twenty fish samples per species (averaging 250 gm) were hot smoked dried whole for 36 hours at an average temperature of 100?C. Packaged hot at the rate of 6 fishes per package for each species (three packs for each packaging treatment i.e. 18 pieces were packed while the remaining 2 pieces were used for initial bacteria load and microbial load). Microbial load (Total Viable Count (TVC), Total Coliform Count (TCC) and Total Fungi Count (TFC)) for the fresh fish was initial hot smoked and finally at the end of 12 weeks was monitored. The TVC (bacterial load) of O. niloticus dropped from (10.6 - 8.4) × 104 (fresh state-hot smoked) and M. rume (9.8 - 7.0) × 104, while C. gariepinus slightly increased from (12.4 - 12.6) × 104. After hot smoking, highest TVC of 8.6 × 104 (OMPBC), 8.3 × 104 (SPBC) and 8.2 × 104 (STPBC) were recorded in C. gariepinus among the 9 packag- ing at 12 weeks. However highest tendency for heavy TVC is in all OMPB with highest bacteria load in the OMPBC (8.6 × 104), 7.6 × 104 (OMPBO) and 6.6 × 104 (OMPBM). After 12 weeks highest ranged TFC of (0.6 - 0.7) × 104 was recorded in M. rume as against 0.2 × 104 recorded in the initial smoked for all. TCC was highest in C. gariepinus (4.0 - 4.3) × 104. Packaging did not limit the existence of micro-organisms. Six bacteria species (Micrococcus (acidiophilus, luteus), Bacillus (subtilis, cereus, aureus), Staphylococcus aureus, Streptococcus lactis, Proteus (vulgaricus, morganii), Pseudomonas aureginosa) and three fungi species (Aspergillus (niger, tamari), Rhizopusnigricans, fusariumoxysporum) were represented in all the packages. On the average five bacteria and two fungi species were represented, excepting for OMPBM and OMPBO with six bacteria species.

Strategic Conception for Sustainable Development of Massive Freshwater Fish in China

[ Objective] To propose strategic conception for sustainable development of massive freshwater fish in China. [ Method] The current development status of massive freshwater fish industry in China was analyzed. On this basis, strategic conception for sustainable development of massive freshwater fish in China was proposed. [Remlt] In order to solve the present problems in the massive freshwater fish industry in China, basic strategies were proposed to develop the massive freshwater fish industry in China. The fishery resources should be capitalized to promote sustainable development of resources. Consumer demand of end-market should be used to drive stable development of the whole industry chain. Consumer demand should be guided to enhance the industrial market position. Processing and distribution channels should be constructed to promote sustainable development of seed and farming industries. Consumer demand at different levels should be used to promote multi-level multi-media health culture. Brand building and operating should be performed to enhance the competitive position of the industry in international and domestic markets. [ Condusion] The study has great theoretical and practical significance for promoting development of the massive freshwater fish industry in China.

Distribution and Relationships of Seven Trace Elements （Cr, Fe, Mn, Ni, Co, Cu and Zn） in Freshwater Fish from Five French Fishing Areas

The concentrations of seven essential trace elements in 149 freshwater fish from eight fish species （European eel, bream, common carp, European catfish, roach, perch, pike and pikeperch） from five different French fishing areas from contaminated and control sites were measured by inductively coupled plasma mass spectrometry after microwave digestion under pressure. Differences in the concentration of elements in the muscles of these species were examined and the mean levels were compared for each species with previous French and European studies. The condition factor and the differences between the control and contaminated sites and between predatory and non-predatory groups, with respect to the concentration of these elements, were also studied.

Sequence analysis and typing of Saprolegnia strains isolated from freshwater fish from Southern Chinese regions

Saprolegniasis,caused by Saprolegnia infection,is one of the most common diseases in freshwater fish.Our study aimed to determine the epidemiological characteristics of saprolegniasis in Chinese regions of high incidence.Saprolegnia were isolated and identified by morphological and molecular methods targeting the internal transcribed spacer(ITS)ribosomal DNA(rDNA)and building neighbor-joining(NJ)and maximum parsimony(MP)phylogenetic trees.The ITS sequences of eight isolated strains were compared with GenBank sequences and all strains fell into three clades:CLADE1(02,LP,04 and 14),CLADE2(S1),and CLADE3(CP,S2,L5 and the reference ATCC200013).Isolates 02 and LP shared 80%sequence similarity with S.diclina,S.longicaulis,S.ferax,S.mixta,and S.anomalies.Further,isolates 04 and 14 shared 80%similarity with S.bulbosa and S.oliviae.Finally,extremely high ITS sequence similarities were identified between isolates S1 and S.australis(100%);CP and S.hypogyna(96%);and S2,L5,ATCC200013 and S.salmonis(98%).This research provides insights into the identification,prevention and control of saprolegniasis pathogens and the potential development of effective drugs.

Productive Performance of Giant Freshwater Prawn （Macrobrachium rosenbergi） Fed Diet Containing Silkworm Pupae （Bombyx mon~ Replacing for Fish Meal

The productive performance of giant freshwater prawn （Macrobrachium rosenbergii de Man） fed diet containing silkworm pupae （Bombyx mori） replacing for fish meal was conducted by focusing on digestibility, growth performance and feed utilization. Five diets of an isonitrogenous of 35 ：e 1% crude protein and isocaloric of digestible energy of 3,200 ±100 kcal/kg were formulated by using silkworm pupae, 0%, 8.6%, 17.2%, 25.8% and 34.7% by weight, replaced for fish meal. Giant freshwater prawn of 19 ± 2.0 g were stocked at 5 ind./m3 in concrete tank of 2.25 ton for three months. The protein digestibility by pepsin enzyme was evaluated in fish meal, silkworm pupae, soybean meal and shrimp meal. The digestibility was significantly difference （P 〈 0.05）. The protein digestibility of fishmeal and soybean meal was higher than silkworm pupae and shrimp meal. The productive performance of prawn in terms of growth rate and feed utilization were not significantly different （P 〉 0.05）. Therefore, silkworm pupae can be replaced for fishmeal in giant freshwater prawn （Macrobrachium rosenbergii de Man） without any adverse effects on productive performance.

江苏省淡水渔业碳汇强度和经济价值估算

根据2014—2023年江苏省淡水渔业养殖产量和捕捞产量数据,计算淡水渔业碳移出量和碳汇价值,并讨论了江苏省碳汇渔业发展面临的问题及对策建议。结果表明,10年间,江苏省淡水养殖碳移出量为21.55万~24.13万t,碳移出总量为226.41万t,占比较高的有鲢、鳙、鲫、草鱼、虾和河蟹;淡水捕捞碳移出量为2.17万~4.07万t,碳移出总量为34.67万t,鱼类、甲壳类和贝类分别占比为66.38%、14.54%和17.36%。根据碳汇市场价格100元/t来计算,养殖碳汇和捕捞碳汇价值年际变化分别为7908.85万~8855.71万元和796.39万~1493.69万元,江苏省淡水渔业碳汇价值合计为9.58亿元。江苏省淡水渔业养殖碳移出量及碳汇价值大于捕捞碳移出量及碳汇价值。

广东省内陆江河鱼类多样性

广东省地属热带和亚热带季风气候区,是我国鱼类资源丰富且社会经济最为活跃的地区之一,其鱼类生物多样性受到较大威胁。在近十几年调查的基础上,系统整理了广东省珠江水系、粤东水系和粤西水系14条河流(区域)的鱼类物种名录,并对其种类组成和分布进行了分析,利用聚类和排序方法探究了广东省内陆江河鱼类的空间分布格局。结果表明,广东省内陆江河共记录有鱼类351种,隶属于21目74科207属。其中,广东省特有鱼类13种,国家重点保护鱼类8种,河海洄游鱼类10种,淡水珍稀濒危鱼类28种,在珠江、粤东和粤西水系均有分布的广布种有52种。根据聚类和排序分析结果,可将14条河流(区域)分为5组:珠江水系和韩江鱼类种类较为相似分为一组;粤西水系和粤东的螺河、赤石河、黄江鱼类种类较为相似分为一组;粤东的黄冈河、榕江和练江各单独为一组。相似性分析结果显示,各组之间鱼类种类组成差异显著(r=0.937,p=0.001)。广东省江河鱼类中,2010年之后出现的种类有223种(含外来种群),约有39%的历史土著种类未出现,土著鱼类资源明显衰退。鱼类栖息地生境破坏、外来种群入侵等是鱼类多样性下降的主要威胁因素。未来需要加强保护区的建设和管理,防控外来种群的扩张,最重要的是从保护鱼类栖息地的角度进行水资源的开发与管理。

土臭素对淡水鱼品质的影响及控制策略研究进展

水产品味道鲜美,营养丰富,是人类摄取食物蛋白的重要来源。但以土腥味为代表的特殊异味在淡水养殖的鱼类中经常出现,不但影响水产品的风味,更降低了消费者的消费意愿,制约着水产品养殖行业的稳定发展。而科学控制和预防水产品中的土腥味是保障水产品质量的重要手段,对满足产业需求具有重要意义,仍需深入研究。本文综述了水产品中以土腥味为典型代表的特殊异味,探讨了以土臭素为代表的异味物质在水产品中造成土腥味的机理,并结合目前控制土腥味的常用方法,对未来水产品异味防控发展趋势进行展望,以期消除水产品中的异味物质,尤其是淡水养殖的水产品中存在的土腥味。

高效液相色谱-质谱法测定淡水鱼中地西泮

建立高效液相色谱-质谱法测定淡水鱼中地西泮。样品用乙腈提取,采用Florisil填料和氨基填料净化,当Florisil填料和氨基填料的质量比为2∶3时,能够有效地吸附淡水鱼基质中的脂肪、脂质和蛋白质等杂质,降低基质效应,提高质谱响应的信噪比。地西泮的质量浓度在0.05~20 ng/mL范围内与色谱峰面积线性关系良好,相关系数为0.9996,检出限为0.15μg/kg,定量限为0.5μg/kg。空白样品加标回收率为84.2%~95.5%,测定结果的相对标准偏差为5.25%~6.83%(n=6)。该方法快速准确,基质效应小,能够满足水产品中地西泮的测定要求。

淡水鱼越冬综合症发病气象指数评估方法研究

为科学预防淡水鱼越冬综合症,降低病害暴发风险,本研究在近年发病情况调查和资料搜集的基础上,深度分析了越冬综合症病害发生的气象背景差异,并建立了淡水鱼越冬综合症发病气象评估方法。通过统计分析关键气象要素,如稳定通过12℃初日、降温过程前期温度、降温过程发生时间、降温幅度和伴随降水量、雨日等,确定了影响鱼类越冬综合症的气象因子。研究发现,除降温和降水外,降温前气象条件也是影响鱼病发生程度的重要因素。基于此,构建了基于风险陷阱理论的升温陷阱指数和综合考虑雨量雨日的降水指数,并开发了鱼类越冬综合症的综合气象指数。结果表明,该综合气象指数能准确反映病害的发生时间和程度,与实际发病情况高度一致。此外,研究还确定了不同病害等级的累计综合气象指数阈值。这一评估方法为淡水鱼越冬综合症的气象监测和预报提供了科学依据。

阳江市淡水鱼产业发展问题研究

为进一步推进阳江市农产品高质量建设,促进淡水鱼产业发展,通过对阳江市淡水鱼产业实地调研及收集到的资料,从育种、生产、加工、销售各环节深入分析了阳江市淡水鱼产业发展现状、问题与短板。认为产业竞争力不足、产业基础设施薄弱、技术投入欠缺和产业整合力度不够是制约阳江市淡水鱼产业发展的主要问题。并提出了发展集约化养殖、加大资金投入、完善水产养殖基础设施、增加技术培训、加大产业整合力度、建设产业专业合作组织、接入市场金融工具等对策建议,为推动阳江市淡水鱼产业发展,全面推进乡村振兴提供助力。

养殖户新品种选择影响因素研究——以特色淡水鱼为例

论文基于2022年特色淡水鱼养殖户调查数据,构建二元Logistic模型,分析影响养殖户新品种选择的5类因素及动因。研究发现,养殖年限、信息获取渠道、苗种质量退化以及参加渔业保险等会对新品种选择产生正向影响,经营者虚假销售、货源不稳定则会对新品种选择产生负面影响,而教育程度、养殖面积、养殖户类型、与行业组织合作、参加技术培训、苗种来源对新品种选择没有显著影响。基于研究结论,有针对性地提出培育新品种使用示范户,加大新品种宣传力度,保障货源稳定,加强苗种经营者管理,完善渔业保险制度等措施来激励养殖户采纳新品种。

电子鼻结合生物胺分析淡水鱼贮藏过程中的品质变化

以三种淡水鱼(草鱼、罗非鱼和鳙鱼)为研究对象,分析了25℃和4℃贮藏条件下色泽、pH值、硫代巴比妥酸反应物质(TBARS)、总挥发性盐基氮(TVB-N)等理化指标的变化,并结合电子鼻和生物胺(BAs)探究在贮藏过程中新鲜度的变化。结果表明,25℃和4℃贮藏条件下,随着贮藏时间的延长,b*值、总色差(ΔE)、生物胺含量、TVB-N和TBARS含量逐渐增大,pH值呈现出先降后升的规律,而L*值和a*值呈现下降趋势。25℃贮藏12 h和4℃贮藏第6天,三种淡水鱼的TVB-N值均超过15 mg N/100 g,均检测到腐胺和尸胺成分,说明淡水鱼开始腐败变质,电子鼻响应信号也均能很好地区分三种淡水鱼新鲜程度变化。综上,贮藏温度和时间是影响淡水鱼新鲜度的重要因素,特征生物胺及电子鼻感应器响应值可以用来判断淡水鱼品质新鲜度变化,评价方法具有可行性。本研究为淡水鱼产品的新鲜度评价提供理论依据。

淡水鱼鱼糜凝胶品质影响因素的研究进展

我国淡水资源十分丰富,淡水鱼产量和养殖量均居世界首位。目前,淡水鱼的消费以“鲜活销售”和“家庭烹饪”为主,深加工比例较低,以鱼丸、鱼豆腐、鱼糕和鱼肠等为代表的鱼糜制品,因其内源性蛋白酶含量较高,在加工中易发生凝胶劣化现象。与海水鱼鱼糜相比,淡水鱼鱼糜的凝胶性较差,因此,提升淡水鱼鱼糜的凝胶性成为目前炙手可热的研究方向。文章基于淡水鱼糜凝胶的形成机理,主要综述了加工工艺、热诱导方式和外源物质添加对淡水鱼鱼糜凝胶品质的影响,为提高淡水鱼鱼糜凝胶品质奠定了理论依据。

淡水鱼腥味物质检测及脱腥技术研究进展

鱼类的肉质鲜嫩,因其高蛋白、低脂肪的营养特性,营养价值丰富,是重要的食品原料。但鱼类自身的腥味物质限制其深度应用。目前鱼类的深加工技术无法完全解决鱼类及其制品的腥味问题,制约了鱼类的标准化、规模化和多元化发展。该文综述淡水鱼类及其制品的腥味形成机理、对比不同腥味物质检测技术差异及可行的脱腥方式,以期为提高淡水产品的竞争力以及推动优质水产品的升级扩展提供技术参考。

武都水库微塑料的赋存特征研究

为探讨水库水体与生物体的微塑料的赋存特征,以武都水库为研究区域,于2022年丰水期采样并分析水库内不同水域表层水和鱼体内的微塑料。结果表明:2022年9月武都水库表层水中的微塑料平均丰度为(63.61±16.26)个/L,库首、库中和库尾微塑料丰度无显著性差异;鱼体胃肠道微塑料平均丰度为(13.61±8.43)个/g,鱼鳃中微塑料平均丰度为(12.22±4.99)个/g;肌肉中微塑料平均丰度为(4.66±3.34)个/g,肌肉中微塑料的丰度显著低于胃肠道和鱼鳃(P<0.05)。微塑料组分和粒径分析结果显示,水体和鱼体微塑料均以聚氯乙烯占比最多,其次为聚酰胺,水体和鱼体中的微塑料均以小粒径(20~50μm)的微塑料为主。相关性分析结果显示,水库水体与鱼体组织中的微塑料在化学组成和粒径组成上显著相关(P<0.05)。