Geosmin and Off-Flavor in Nile Tilapia (Oreochromis niloticus)

Abstract

The concentration of geosmin (1,10-trans-dimethyl-trans-9-decaol) in fresh tilapia were analyzed by applying high-vacuum distillation, extraction and gas chromatography techniques. The distribution of geosmin in the fish was determined by examining tissues from various parts of tilapia, along with the rates of geosmin absorption and purging. Analysis showed that when geosmin was added to fish flesh at concentrations ranging from 2.8 to 390 μg per kg of flesh, the rate of recovery was 51 to 89%. Sensory evaluation detected muddy flavor in freshwater tilapia with geosmin content ranging from 7.55 to 9.85 μg/kg of fish flesh. However, panelists failed to detect muddy flavor in brackish water tilapia that contained geosmin only in the range of 1.5 to 2.6 μg/kg. Among various tissues of the fish, the intestines contained the highest geosmin concentration, and appeared in descending order in the abdominal, skin and muscle tissues. After holding for 2 h in water with 5 and 50 μg/l geosmin, tilapia absorbed 17.6 and 42.2 μg/kg geosmin in the flesh, respectively. Holding the fish over longer periods in water with higher geosmin content resulted in a greater amount of absorption. In contrast, transferring muddy-flavored fish to static clean water purged geosmin from the fish but it required at least 16 days to eliminate the muddy flavor.     

Effects of Preservation Methods On Geosmin Content and Off-Flavor in Nile Tilapia (Oreochromis niloticus)

Abstract

In this study, the masking or reduction of off-flavor in tilapia due to various preservation methods such as salting, drying, frying, smoking, microwave heating, marinating and fermentation with carbohydrate mixture (som fak preparation) was investigated by subjecting the processed tilapia to sensory evaluation and analyzing the concentrations of geosmin (1,10-trans -dimethyl-trans -9-decaol) in the processed samples. Dry salting or brining muddy-flavored fish and then drying either by hot air at 50°C or sun-drying resulted to only a slight reduction in the geosmin content of the product. Deep-frying reduced the muddy flavor intensity and geosmin content in salted-dried tilapia. Pretreatment of tilapia fillets with acidified brine before smoking reduced geosmin content and masked the muddy flavor in the smoked product. Microwave cooking of fresh muddy-flavored tilapia showed no effect on its geosmin content nor its off-flavor. Marinating tilapia in acetic acid solution resulted in decreased muddy flavor, and longer marinating period led to lower geosmin content in the product. The geosmin content of som fak made from muddy-flavor and non-muddy-flavor tilapia differed significantly, although sensory evaluation yielded no significant differences between the two types of som fak, and the taste panelists preferred the product fermented for 3 days.     

The Cost of Production of Giant Clam Seed Tridacna gigas

The costs of providing giant clam seed in Australia are examined for alternative annual volumes of production. Considerable economies of scale in production are available, both in relation to labor costs and non-labor costs (mostly capital costs). The fall in per-unit cost of producing giant clam seed is considerable when annual production is expanded from 100,000 to 500,000 seed clams per year. At 10% rate of interest, the unit cost per clam seed falls from $1.43–$2.04 at a production level of 100,000 to $0.41–$0.55 at a production level of 500,000. Per-unit operating costs also fall. They decline from $1.01–$1.22 to $0.29–$0.35. This suggests that there are likely to be cost economies in having large centralized hatcheries.     

浅析民营企业的成本控制

民营企业是我国社会主义市场经济的重要组成部分,其成本控制是管理工作的长期课题,如何更合理、更科学地进行成本控制,文章从成本管理与控制的重要性即增强成本观念、实行全员成本管理,注重成本效益观,扩大成本控制范围,加强成本信息管理和内部控制制度,提高信息反应能力和加强信誉成本控制五个方面进行了阐述。     

Cost of regulations on US catfish farms

Understanding the economic effects of regulations on US aquaculture farms provides insights into which compliance costs create the greatest compliance burden on farms. This can further guide strategies to improve the efficiency of regulatory frameworks and potentially reduce on-farm compliance costs while maintaining adequate oversight. This study estimated the regulatory compliance burden on US catfish farms as part of a national effort to quantify the cost of regulations on US aquaculture farms. Completed survey interviews of catfish farms in the major catfish-producing states covered 63% of the total US catfish production area. Total regulatory costs of the US catfish industry were estimated at $45 million annually. Lost farm revenues (measured as the value of lost production, the value of markets lost from regulations, and the value of business opportunities lost because of regulations) were estimated to be $35 million per annum. Catfish-producing states outside the Alabama/Arkansas/Mississippi region had the highest ($2856/ha) and Alabama the lowest ($1127/ha) regulatory costs per hectare among the surveyed states. The greatest regulatory cost burden on catfish farms ($18 million) was caused by environmental regulations related mostly to the management of federally protected piscivorous migratory birds, followed by labor regulations ($12 million), and taxes/insurance ($7 million). Regulatory costs ($/kg) were 2.6 times higher on smaller (<80 ha) farms relative to larger (>300 ha) farms. Attention is needed to identify alternative regulatory frameworks that provide the same degree of regulatory oversight but are more cost-efficient.     

Cost benefit analysis of fisheries management plans

The management of freshwater fisheries in France is generally entrusted to angling associations, which are in turn grouped into departmental federations. These associations, act under State supervision to protect the aquatic environment and develop recreational fisheries. The National Fishing Council has developed a general method for the formulation of departmental fishery management plans. More than half the departments of France have been involved in this programme since 1995. The approach focuses on the potential number of adult wild fish in each homogeneous ecological unit called a 'context'. The cost of any rehabilitation work needed to restore habitat and to place the context under self-sustaining management (called 'patrimonial management') is estimated. Examples of the way in which cost-benefit analysis helps determine the economic viability of management plans are drawn from the Indre and Hérault, two departments with contrasting ecological and fishery situations. The analysis takes into account the value of wild fish in relation to stocked fish.     

饲料采购成本控制数学模型的建立

本文在分析养殖企业成本控制的关键环节,及其成本发生情况的基础上,研究养麸殖企业饲料采赡成本控制,科学地处理各成本项目,构建养殖企业饲料采购成本控制的模型。并以实全祭该数学模型在养殖企业饲料采购过程中科学控制成全的运用。     

浅谈工厂化养鱼项目工程造价的控制

工厂化养鱼是渔业现代化的重要发展方向,它集生物、机械、工程、材料、机电、自动化、信息控制等高新技术为一体,实现对养殖的主要环境因子,包括水温、水质以及投饵、消毒、杀菌、污水处理等的半人工或自动控制,并实现优化。目前我国海水工厂化养殖发展迅猛,到2001年全国养     

浅谈工厂化养殖项目工程造价的控制

工厂化养鱼是渔业现代化的重要发展方向,它集生物、机械、工程、材料、机电、自动化、信息控制等高新技术为一体,实现对养殖的主要环境因子,包括水温、水质以及投饵、消毒、杀菌、污水处理等的半人工或自动控制,并实现优化。目前我国海水工厂化养殖发展迅猛,到2001年全国养鱼面积已达130万ｍ2以上,形成了一项新兴产业。与此同时,项目在建设过程中也存在很多问题,如:项目规模的确定、工程设计优化、施工质量监督、工期和投资控制等。有些项目工程质量好,工期短,但工程投资大;而有些项目虽然投资较少,但工艺技术落后,设备不配套,工程质量…     

远洋鱿鱼钓船营运成本分析

对远洋鱿鱼钓船的营运成本进行了分类，通过计算确定出中国作业于北太平洋渔场的远洋鱿鱼钓船营运成本中各部分费用所占的比例，提出应把降低燃油费和船员费用作为远洋鱿鱼钓船进行价值工程的重点以及降低营运成本的一些措施。     

凡纳滨对虾养殖成本控制浅析

本文主要从养殖管理、饵料选择投喂及苗种选择等几方面介绍了凡纳滨对虾在养殖过程中成本控制技术要点,为指导生产实践提供借鉴。     

农村劳动力职业技能培训的成本效益分析

目前,我国农村劳动力职业技能培训工作已经取得各地政府有关部门和社会各界人士的关注与支持,然而,研究表明,该项工作的效果并不如想象的那么明显,农村劳动力参与职业技能培训的热情也没有想象的那么高涨。从经济学视角出发,运用成本效益理论对参与农村劳动力职业技能培训工作的各方面进行分析,可以发现更深层次的影响因素,进而实现对该项工作的改进。     

Cost minimization and input substitution in the production of gilthead seabream

Abstract

This paper studies cost minimization decisions by utilizing a simple bioeconomic model for gilthead seabream (Sparus aurata). This model is based on a biological growth model which accounts for the effects of temperature and ration size. Although the implicit production function derived from the growth model is shown to be quasiconcave, it is not homothetic nor quasilinear. Further, technology shows increasing returns with respect to ration size and harvesting time. Optimization decisions are analyzed in two different contexts, a restricted biological setting and an expanded economic problem. It is shown that the optimal ration size increases for the latter context, reaching values commonly accepted in current industrial practice. Even though the elasticity of substitution to the shadow input prices is positive at the optimal ration size, the latter is rather robust to changes in input prices. However, optimal costs show larger sensitivity to the labor price than to the feeding and managerial costs.     

渔业管理方法及制度效应——交易成本的视角

目前渔业管理方法众多,每种方法的成败也有着不同的评价标准与目标。文章对四种主要的管理方法进行分析并简要概括了优势和不足,在此基础上用信息成本、协调成本、战略成本对这四种渔业管理方法进行评估,指出成功的渔业管理需要将这些管理方法本身固有的成本和收益、优势和劣势与特定渔业的具体情况相匹配。     

Cost benefit of hatchery-reared barramundi, Lates calcarifer (Bloch), in Queensland

Abstract. Recreational fishing for barramundi, Lates calcarifer (Bloch), is a major contributor to the economy of Queensland, generating an estimated $A 8 to $A 15 million per annum. The Queensland Department of Primary Industries is investigating the feasibility of enhancing barramundi populations with fish produced in fish hatcheries. Cost benefit analysis of the Department's stocking of baaamundi in Lake Tinaroo indicates that each dollar spent on the programme generates a potential $A 31 of economic benefit to the Queensland economy.     

Cost comparisons of rearing larvae of freshwater shrimp,Macrobrachium acanthurus and M. rosenbergii,to juveniles

Costs were determined for rearing larval Macrobrachium rosenbergii (De Man) and M. acanthurus (Wiegmann). Rearing was conducted in two phases. First-phase rearing (first 10 days) was conducted in conical fiberglass tanks with recirculated, filtered, brackish water; second-phase rearing (final 30 days) was done in aerated 1 000-l concrete tanks. To minimize water quality problems and debris accumulation in second-phase rearing, larvae were transferred every 4 to 5 days to a new tank of clean water. Larval food consisted of newly hatched Artemia and either freshly ground fish or freeze-fried fish.Mean survival in five M. rosenbergii rearing trials was 43% in 40 days at a final density of 12 juveniles per liter. Mean survival of four M. acanthurus trials was 25% in 44 days at a final density of 3 juveniles per liter. Average total cost of labor, operation (electricity), food and water per thousand juveniles produced was $3.56 for M. rosenbergii and $13.42 for M. acanthurus.Extrapolation of results to larger (3 000-l) second-phase rearing tanks showed M. rosenbergii rearing cost could be reduced to $\text{\$1.87}\text{1 000}$.     

An Analysis of Biological, Economic, and Engineering Factors Affecting the Cost of Fish Production in Recirculating Aquaculture Systems

Aquaculture production in recirculating systems has been the focus of research and development efforts for decades. Although considerable resources have been expended on these systems in the private sector, there is a scarcity of data on the economic or engineering performance of commercial scale recirculating production systems. This paper presents the results of a computer simulation of tilapia production in a small recirculating production system. Much of the performance data has been developed at a demonstration facility at North Carolina State University. Given the assumptions of the base case simulation, the cost of producing a kilogram of tilapia in the recirculating system described is estimated to be $2.79 ($1.27/lb). The results of a model sensitivity analysis indicate that while improvements in the performance efficiency of system components did not greatly affect fish production costs, reductions in feed costs and improvements in the feed conversion ratio caused the greatest reduction of production cost of all of the operational variables investigated. The analysis further indicates that the greatest gains to be realized in improving profitability are those associated with increasing the productive capacity or decreasing the investment cost of a recirculating fish production system.     

Design and Cost Analysis of a Self‐contained Mobile Laboratory for Commercial‐scale Aquatic Species Cryopreservation

Although aquatic species cryopreservation protocols have been studied around the world over the past 60 yr., germplasm repository development efforts and commercialization have begun only recently. The goal of this project was to develop a self‐contained mobile laboratory for on‐site high‐throughput cryopreservation of aquatic species. The objectives of this study were to: (1) identify how a mobile laboratory would function in different operational scenarios, (2) customize an enclosed cargo trailer to function as a mobile laboratory, (3) evaluate the laboratory layout and ability of cryopreservation equipment to operate from generator power, and (4) document the investment costs for private and public groups to integrate a mobile laboratory into an existing cryopreservation facility at three levels of automation and estimate the total cost per trip based on hypothetical assumptions for two scenarios (aquaculture production and repository development). There were three operational designs identified for the mobile laboratory: (1) self‐contained work inside the unit using generator power, (2) work inside the unit using external facility power, and (3) using the equipment inside of a host facility. The investment costs for a base‐level mobile laboratory ranged between US$5670 and US$5787 for private groups and between US$5208 and US$5315 for public groups. With the addition of a range of automated processing equipment, total investment costs ranged from US$13,616 to US$103,529 for private groups and US$12,494 to US$94,891 for public groups. The total cost per trip to cryopreserve sperm of 59 blue catfish, Ictalurus furcatus, males to produce 6300 0.5‐mL French straws was estimated to range from US$6089 to US$14,633 for private and between US$5703 and US$16,938 for public groups depending on the level of automation. Total cost per trip to cryopreserve sperm of 500 males of five different species in the genus Xiphophorus to produce 641 0.25‐mL French straws was estimated to range from US$6653 to US$7640 for private and US$7582 to US$8088 for public groups depending on level of automation. Overall, a commercial‐scale mobile laboratory was developed that can assist current germplasm activities and support future repository and industry development, and the layout information provided can help others to design and build comparable units.     

Prolonged Culture Period on Production Cost and Factor Input: A Case from the Pacific Oyster,Crassostrea gigas,Farming Industry in Yunlin County,Taiwan

The Yunlin coastal area is the largest oyster culture in Taiwan; however, the oyster farmers reported the negative impact of a prolonged oyster culture period and an increased operating cost in 2010. This study uses the translog cost function to consider the possibility of an oyster culture period extension to estimate oyster cost elasticity, own‐price elasticities, and cross‐price (substitution) elasticities, to evaluate whether the oyster farming industry in Yunlin County has economies of scale, and to assess the relationship with a substitution of inputs. We found that the Yunlin oyster culture has economies of scale, and that the oyster farmers can expand production scale to reduce costs. The own‐price elasticities of demand for inputs are less than 1, indicating fairly inelastic factor demands in oyster production. The oyster farming industry displays strong substitutability between the prolonged culture period and capital input, suggesting that the oyster farming industry is more responsive to a higher prolonged culture period cost, in terms of capital input.