Parasite Infections in Danish Trout Farms

Samples from 5 Danish freshwater trout farms rearing rainbow trout (Oncorhynchus my kiss) were examined for parasite infections from October 1993 until November 1994 and recorded parasites are listed. In addition, results from an examination of a mariculture net cage system are presented as well. A total of 10 metazoan and 10 protozoan parasites were recorded. The metazoans included Gyrodactylus derjavini, Gyrodactylus salaris, Eubothrium crassum, Triaenophorus nodulosus, Proteocephalus sp., Diplostomum spathaceum, Tylodelphus clavata and Argulus foliaceus from the freshwater farms. The protozoans Hexamita salmonis, Ichthyobodo necator, Ichthyophthirius multifiliis, Apiosoma sp., Epistylis sp., Trichodina nigra, T. mutabilis, T. fultoni, Trichodinella epizootica, and an Ichthyophonus like intestinal parasite were also detected in the freshwater trout farms. Based on lectin binding studies, few fish were found positive for the myxosporean parasite PKX although no clinical cases were reported. In the mariculture system, Lepeophtheirus salmonis and Caligus elongatus were found.     

A simple model for predicting ecological impacts of introduced aquatic organisms: a case study of common carp, Cyprinus carpio L., in the Sepik-Ramu River Basin, Papua New Guinea

Abstract Practical models for predicting the impacts of introduced biota are urgently required to assess the benefits and risks of introductions. The simple method described predicts the ecological consequences of an introduction through potential competition between species based on elementary niche classifications. The model's predictions are tested against field data for common carp, Cyprinus carpio L., which escaped from fish farms during a study of the feasibility of fish stock enhancement in a large river basin. Recorded effects of carp are based on pre- and post-carp gillnet catches, observations of local villagers, socio-economic censuses and other sources of data. The predicted ecological interactions of common carp are in broad agreement with those recorded. The method can assist pre-introduction assessments and is particularly useful where limited data exist. In this particular study, common carp have contributed significantly to an improved capture fishery by fortuitous accident; production from aquaculture was negligible. High niche overlap between carp and certain resident fish species is predicted and this may be of more consequence in highland than lowland regions. Organisms introduced/transferred for aquaculture should be assessed within a much wider forum. The intended impacts of an introduction/ transfer, which in the case study were entirely erroneous, is an area in need of considerable attention.     

小球藻对罗非鱼养殖水体水质及细菌群落结构的影响

本研究通过向罗非鱼养殖水体中添加小球藻,旨在探究其对养殖水体N、P降解和微生物群落调控的最佳浓度.分别设置对照组(NC)、低浓度组(LC)、中浓度组(MC)和高浓度组(HC),探究不同浓度小球藻对罗非鱼养殖水体中N、P的改善效果,并采用16S rRNA高通量测序技术分析养殖水体细菌群落结构变化.与其他处理组相比,HC组...     

基于室内循环水系统的大口黑鲈3个品系养殖性能评估

在室内循环水系统开展大口黑鲈(Micropterus salmoides)3个品系养殖生长对比试验。大口黑鲈‘优鲈1号’、‘优鲈3号’、‘浙鲈2号’随机分配到9个养殖缸中,每组设3个重复,每个缸中30尾鱼（初始均重6.08±0.12g）,养殖8周。试验鱼存活率高于98.89%(P>0.05),体生长‘优鲈3号’>‘优鲈1号’>‘浙鲈2号’,但无显著差异(P>0.05);‘浙鲈2号’的体长变异系数和体重变异系数最小(P>0.05)。各品系形态学指标无显著差异(P>0.05)。饲料系数和蛋白质效率最高值分别出现在‘浙鲈2号’和‘优鲈3号’(P<0.05)。肌肉常规营养组成和氨基酸组成均无显著差异(P>0.05)。‘浙鲈2号’的肠蛋白酶和肝脏蛋白酶活性最低(P<0.05)。各品系血清中10项生化指标均无显著差异(P>0.05)。本试验表明大口黑鲈‘优鲈3号’生长性能相对较好;‘浙鲈2号’在体增长、营养组成和血清生理指标等方面的表现和优鲈系列相近,显示出良好的育种潜力。     

The effect of choice of targeted market,production scale,and land tenure on the economics of integrated tilapia-prawn production

Integrated aquaculture systems have the potential to enhance the environmental sustainability of aquaculture production, if economically feasible. Data from integrated tilapia-prawn production trials were used to develop economic-engineering enterprise budgets for ponds with and without substrate that targeted two different types of markets, using two production scales and two forms of land tenure. Inclusion of substrate increased investment and fixed costs and decreased net returns. Recreational markets (live tilapia for fee fishing and live prawns as bait) were profitable, but sales to supermarkets were not. Production scale and land tenure affected economic outcomes with increased pond size and leasing ponds demonstrating greater profitability. Results provide evidence of the need to carefully evaluate economic trade-offs associated with varying commercial-scale applications to increase the likelihood of adoption of new technologies.     

中国经济海藻养殖技术概况与展望

我国是全球海藻生产和消费大国。当前,我国海藻养殖种类以海带、紫菜、江蓠和裙带菜等为主体,兼有小规模养殖的羊栖菜、鼠尾藻、麒麟菜、石花菜、礁膜、浒苔、长茎葡萄蕨藻等。海藻养殖方式包括浅海养殖、潮间带养殖和陆基养殖。近年来,在全球气候变化、海水污染、海岸工程等多重压力下,海藻养殖环境不佳,养殖病害多发;另外,海洋生态文明建设大背景下的近海水域利用政策变化,对海藻养殖产业及其养殖技术提出了新的要求与挑战。对我国海藻养殖技术进行回顾,总结经验、查找不足,提出新思路、新方法,以期为我国海藻养殖产业可持续发展提供支撑。     

大型养殖工船的结构设计

大型养殖工船主要在深远海海域养殖作业,在满足各种作业工况及养鱼布置的条件下要保证船体结构具有足够的强度,需要对养殖工船进行结构设计工作。由于养殖工船船型和使用工况比较特殊,目前还没有根据其特殊性而专门编写的现行规范。本船根据养殖工船总体布置和装载等特点,参照双壳油船规范中适用章节要求计算出船体结构的基本尺寸和规格,再根据其实际装载情况建立有限元模型,采用有限元方法计算其结构强度。计算和分析结果显示:通过双壳油船规范计算的结构尺寸、规格基本满足要求;局部结构强度达不到强度衡准要求的,通过结构加强后,可满足强度衡准要求。通过采用规范中相似船进行船体结构基本设计,再利用有限元方法分析校核结构强度,经验证该计算方法满足结构设计要求。     

An improved YOLOv3 algorithm to detect molting in swimming crabs against a complex background

Traditional methods of breeding soft-shell crabs mainly rely on manual identification, which has high costs regarding manpower and resources. Manual inspection may also interfere with crabs’ molting, causing molting failure, and possibly even death, which is costly and inefficient. This paper combines an improved YOLOv3 algorithm with an adaptive dark-channel defogging algorithm to realize the real-time detection of whether a swimming crab in a single-crab basket-culture system is molting. For learning more features, affine, rotation transformation and local occlusion are used to augment the training data to simulate the difficulty of identification caused by occlusion, in case molting may occur under distorted viewing conditions in real culture environments. A k-means++ clustering algorithm is used to obtain prior boxes matching the size of the carapace throughout the entire breeding cycle, and so improve the Intersection over Union (IOU). The identification network itself can have its network structure pruned and the non-maximum suppression function modified to increase rapidity and accuracy; the improved network can recognize and give early warning of the early stage of molting. The precision of the improved model in clean water reaches 100 %, and the running speed was 31 FPS. In turbid water where the prediction confidence is lower than the cut-in threshold of defogging algorithm set as 0.8, the precision of the improved model was over 91 %, and the speed can still maintain about 7 FPS.     

聚β-羟基丁酸酯来源及其在水产养殖中的应用

聚β-羟基丁酸酯(poly-β-hydroxyalkanoates,PHB)是发现最早的一种聚羟基链烷酸酯(polyhydroxyalkanoate,PHA),属于聚酯类化合物。1925年法国学者Lemoigne首次在巨大芽孢杆菌(Bacillus megaterium)细胞中发现分离并提取出了聚β-羟基丁酸酯[1]。聚β-羟基丁酸酯具有热塑性、组织亲和性、光学活性、生物可降解性和生物相容性等多种优良特性,同时还可利用再生资源进行生物合成,在工业、环保、医药等领域有广泛应用[2]。有研究表明,聚β-羟基丁酸酯常在营养不均衡的条件下作为微生物细胞中能量和碳的来源[3]。     

Life cycle assessment of aquaculture systems: Does burden shifting occur with an increase in production intensity?

Life cycle assessment (LCA), a tool used to assess the environmental impacts of products and processes, has been used to evaluate a range of aquaculture systems. Eighteen LCA studies were reviewed which included assessments of recirculating aquaculture systems (RAS), flow-through systems, net cages, and pond systems. This review considered the potential to mitigate environmental burdens with a movement from extensive to intensive aquaculture systems. Due to the diversity in study results, specific processes (feed, energy, and infrastructure) and specific impact categories (land use, water use, and eutrophication potential) were analyzed in-depth. The comparative analysis indicated there was a possible shift from local to global impacts with a progression from extensive to intensive systems, if mitigation strategies were not performed. The shift was partially due to increased electricity requirements but also varied with electricity source. The impacts from infrastructure were less than 13 % of the environmental impact and considered negligible. For feed, the environmental impacts were typically more dependent on feed conversion ratio (FCR) than the type of system. Feed also contributed to over 50 % of the impacts on land use, second only to energy carriers. The analysis of water use indicated intensive recirculating systems efficiently reduce water use as compared to extensive systems; however, at present, studies have only considered direct water use and future work is required that incorporates indirect and consumptive water use. Alternative aquaculture systems that can improve the total nutrient uptake and production yield per material and energy based input, thereby reducing the overall emissions per unit of feed, should be further investigated to optimize the overall of aquaculture systems, considering both global and local environmental impacts. While LCA can be a valuable tool to evaluate trade-offs in system designs, the results are often location and species specific. Therefore, it is critical to consider both of these criteria in conjunction with LCA results when developing aquaculture systems.