Impacts of climate change on snakehead fish value chains in the Lower Mekong Basin of Cambodia and Vietnam

ABSTRACT

The productive fisheries of the Lower Mekong Basin of Cambodia and Vietnam are essential to the food security and nutrition of 60 million people. Yet these fisheries, both culture and capture, are susceptible to the impacts of climate change. This article reports on a study undertaken to examine the vulnerability, as perceived by snakehead (Channa striata) fish farmers in Vietnam and fishers in Cambodia, to the impacts from climate change. Perceived impacts on various actors in the value chain are identified, as well as adaptation strategies currently being utilized and planned for the future. Recommendations are suggested to contribute to assisting snakehead farmers and fishers in adapting and preparing for the impacts of climate change.     

Weaning methods using formulated feeds for snakehead (Channa striata and Channa micropeltes) larvae

The culture of snakehead fish (Channa striata and Channa micropeltes) in Vietnam is limited, and snakehead culture has been banned in Cambodia, because traditional practices include capture of fingerlings from the wild as seed, as well as capture of small‐size (also known as trash fish or low‐value) fish. As hatchery breeding technology has improved, we investigated the optimal weaning practices for these two species. Both laboratory experiments and farm trials were conducted. For C. striata, the optimal weaning procedure is to begin at 17 days after hatch (dah) and wean the fish at 10% replacement of live feed with formulated feed per day. However, for C. micropeltes, the optimal procedure is to wait until 40 dah to begin weaning and then to wean the fish with a 10% replacement of live feed with formulated feed every 3 days. These results should enable farmers to domesticate snakehead culture in Vietnam and Cambodia and eliminate reliance on fish captured from the wild as both seed and feed.     

Emaciation of pond-cultured snakehead, Channa striatus (Fowler)

Abstract. A new disease condition which may affect up to 20% of a population has been recognized in pond cultured snakeheads, Channa striatus (Fowler). Clinically, affected fish are inappetent and severely emaciated; histologically and ultrastructurally, emaciated pond reared snakeheads display extensive striated myofibrillar and sarcoplasmic degeneration and necrosis with inflammatory changes.     

Priority knowledge needs for management of migratory fish species in Cambodia

Despite their economic and ecological importance, migratory fishes of the Lower Mekong Basin (LMB) remain understudied, which hampers effective management to sustain valuable fisheries and address serious threats such as habitat degradation, development and overharvest. From a list of potential knowledge needs, a group of fisheries professionals most frequently identified six top priorities for managing migratory fishes in Cambodia: (1) population abundances and trends, (2) life cycles and life history, (3) migration timing and triggers, (4) migration routes and distances, (5) locations of key habitats and spawning areas, and (6) environmental and habitat requirements. These needs are discussed along with nine relevant methodologies for addressing them, including fisheries-dependent and fisheries-independent sampling, reproductive techniques and captive studies, otolith and genetic analysis tools, and tagging and imaging techniques. A suggested research framework is also presented to inform adaptive management of migratory fishes. While emphasis is given to Cambodia, the analysis is also applicable to other LMB countries, given that migratory fishes occur throughout the basin and migrate across borders. It is suggested that a robust research and monitoring agenda is required to prioritise knowledge needs and select appropriate methodologies to answer questions vital to inform sustainable migratory fish management in Cambodia.     

Assessment of farmed tilapia value chain in Ghana

The study assessed the value chain of farmed tilapia in Ghana. A survey conducted in 2012 provided data on key actors, flow of products and information, costs and margins, and relationship among actors. The study showed that all key actors in the value chain: input suppliers; fish farmers; traders; and food services had positive margins except fish farmers. Input suppliers accrued most of the margins generated along the chain. The performance of chain actors was assessed using a factor evaluation matrix, which showed that product offering may be the strength at each stage of the value chain. The efficiency and profitability of tilapia value chain in Ghana can be improved by having well-defined payment transaction with customers, persistent relationships with customers, and good information management such as keeping good records on costs and revenues. Fish farming could be more profitable if farmers reduced their variable costs, priced their fish using a cost plus or percentage markup approach, and adopted target marketing.     

The Economic Impact of the Florida Cultured Hard Clam Industry

Abstract

The objective of this study was to estimate the economic impact on the Florida economy generated by the cultured hard clam industry. Florida certified shellfish wholesalers that handle Florida cultured hard clams were interviewed by telephone survey to determine the number and value of clams that they process, the sources of their clams, prices received, and the marketing channels (wholesale, retail, restaurant, and consumer) where they sell their clams. Of the three regions in the state, northwest Florida handled two-thirds of clams cultured in Florida. Firms obtained their clams from within their own region as well as from the other two regions in Florida. The Florida cultured hard clam wholesale and processing industry had $21.8 million in sales in 1999. Around 43 percent of these sales were within the state and 57 percent of them were to out-of-state locations, including international destinations. Regardless of the geographic destination of the cultured clams sold by clam firms, the majority was sold to other wholesalers. The total economic impact of the clam industry on Florida, after accounting for direct, indirect, and induced impacts, was $33.9 million in output, $9.0 million in labor income, and $12.1 million in value added.     

Effect of fish-meal replacement with poultry by-product meal on the growth, tissue composition and hematological parameters of largemouth bass (Micropterus salmoides) fed diets containing different lipids

We conducted a 12-week feeding trial with largemouth bass (LMB) to examine the interactive effects of non-fish dietary proteins with different lipid sources on the performance of LMB (3.4 g ± 0.05 g). Practical diets contained poultry by-product meal (PBM) in place of fish meal on a digestible-protein basis, and 12% blood meal (BM). Diets were supplemented with 10% lipid as canola (CAN), chicken (CHK), CHK + MFO (50 : 50), menhaden fish oil (MFO) or CHK + CAN (50:50). A commercial trout diet (SC) was included as a positive control. Growth, survival, feed intake (FI), feed conversion ratio (FCR), protein efficiency ratio (PER), body composition, fatty acid composition of liver and muscle, hematological parameters and lysozyme and alternative complement activity (ACH50) were measured to assess diet effects. Weight gain (23.8 ± 1.8 g), survival (92 ± 4%), FI (44.3 ± 4.1 g), FCR (2.1 ± 0.1) and PER (1.3 ± 0.04) of LMB did not differ among the replacement diets. However, weight gain (38.5 ± 1.5), FI (53.9 ± 1.1), and PER (1.6 ± 0.1) of LMB fed the SC diet was higher and FCR (1.4 ± 0.1) was lower than that of fish fed the test diets. No signs of essential fatty acid deficiency were observed, although tissue concentrations of n-3 highly unsaturated fatty acids declined markedly in LMB fed diets without fish oil. Lymphocytes were elevated in fish fed diets with ≥ 7% n-3 fatty acids. Fish fed diets with 10% MFO or CHK + MFO had higher ACH50 than fish fed the diet with 10% CHK. There were no differences in serum lysozyme activity among fish fed the test diets. Hematocrit, hemoglobin, ACH50, and lysozyme activity were higher in fish fed the SC diet than in those fed the test diets. Regardless of lipid source, the ACH50 and lysozyme activity were greatly reduced in LMB fed PBM diets compared to LMB fed diets with 30% fish meal in a previous trial. The amino acid composition of the PBM was similar to that of fish meal. However, the availability of some essential amino acids from PBM to LMB may have been limited, and poor diet palatability caused by BM also may have reduced feed intake and performance of LMB.     

Cyanide-free Net-caught Fish for the Marine Aquarium Trade

The International Marinelife Alliance (IMA) has been training collectors in the Philippines and Indonesia to use barrier-nets rather than sodium cyanide to capture marine-aquarium fish. Despite the training, collectors have been slow to switch to using nets because they can earn more using cyanide. A new Philippine export company has agreed to pay the collectors more for net-caught fish and to adhere to standards being set by the USA-based Marine Aquarium Council. The IMA is monitoring the collectors and conducting cyanide testing to certify that the fish are net-caught and totally cyanide-free. Clearance certificates now accompany shipments of these marine-aquarium fish being shipped to wholesalers and retailers associated with the American Marine Dealers Association (AMDA) situated in the USA and Canada. AMDA members are being surveyed to assess whether the net-caught fish are more cost competitive compared to cyanide-caught fish for the marine ornamental fish trade because of reduced mortality through the chain from reef to retailer.     

Evaluation of Stocking Density during Second‐Year Growth of Largemouth Bass,Micropterus salmoides,Raised Indoors in a Recirculating Aquaculture System

Largemouth bass (LMB), Micropterus salmoides, are a highly desirable food fish especially among Asian populations in large cities throughout North America. The primary production method for food‐size LMB (>500 g) has been outdoor ponds that require two growing seasons (18 mo). Indoor, controlled‐environment production using recirculating aquaculture system (RAS) technologies could potentially reduce the growout period by maintaining ideal temperatures year‐round. Researchers conducted a 26‐wk study to evaluate optimal stocking densities for growout of second‐year LMB to food‐fish size in an indoor RAS. LMB fingerlings (112.0 ± 38.0 g) were randomly stocked into nine 900‐L tanks to achieve densities of 30, 60, or 120 fish/m³ with three replicate tanks per density. The RAS consisted of a 3000‐L sump, ¼ hp pump, bead filter for solids removal, mixed‐moving‐bed biofilter for nitrification, and a 400‐watt ultraviolet light for sterilization. Fish were fed a commercially available floating diet (45% protein and 16% lipid) once daily to apparent satiation. At harvest, all fish were counted, individually weighed, and measured. Total biomass densities significantly increased (P ≤ 0.05) with stocking rate achieving 6.2, 13.2, and 22.9 kg/m³ for fish stocked at 20, 60, and 120 fish/m³, respectively. The stocking densities evaluated had no significant impact (P > 0.05) on survival, average harvest weight, or feed conversion ratio which averaged 92.9 ± 5.8%, 294.5 ± 21.1 g, and 1.8 ± 0.3, respectively. After approximately 6 mo of culture, LMB did not attain target weights of >500 g. Observed competition among fish likely resulted in large size variability and overall poor growth compared to second‐year growth in ponds. Additional research is needed to better assess the suitability of LMB for culture in RAS.     

Seasonal meso‐ and microhabitat selection by the northern snakehead (Channa argus) in the Potomac river system

Lapointe NWR, Thorson JT, Angermeier PL. Seasonal meso‐ and microhabitat selection by the northern snakehead (Channa argus) in the Potomac river system.
Ecology of Freshwater Fish 2010: 19: 566–577. © 2010 John Wiley & Sons A/S Abstract – The northern snakehead (Channa argus) is a large piscivorous fish that is invasive in eastern Europe and has recently been introduced in North America. We examined the seasonal habitat selection at meso‐ and microhabitat scales using radio‐telemetry to increase understanding of the ecology of this species, which will help to inform management decisions. After the spawning season (postspawn season, September–November), northern snakeheads preferred offshore Eurasian water‐milfoil (Myriophyllum spicatum) beds with shallow water (～115 cm) and soft substrate. In the winter (November–April), these fish moved to deeper water (～135 cm) with warmer temperatures, but habitat selection was weak at both scales. Northern snakeheads returned to shallower water (～95 cm) in the prespawn season (April–June) and used milfoil and other cover. Habitat selection was the strongest at both meso‐ and microhabitat scales during the spawning season (June–September), when fish preferred macrophytes and cover in shallow water (～88 cm). Our results help to identify habitats at the risk of invasion by northern snakeheads. We suggest that control efforts and future research focus on shallow waters, and take into consideration the seasonal habitat preferences.     

Economic Analysis of Alternative Snakehead Channa striata Feed

The use of low-value small-sized fish (LVSSF) both as aquaculture feedstuff for snakehead and for human consumption in Vietnam and Cambodia could result in demand outstripping supply as human population and aquaculture production grow. Replacing LVSSF for snakehead aquaculture with pelleted feed would reduce the pressure on stocks of LVSSF. This study addresses the economics of this replacement strategy for snakehead culture in Vietnam. Economic engineering methods were used to assess the effects of pelleted feed for low, medium and high-productivity scenarios. The study compared net present values (NPV), internal rates of return (IRR) and differences in NPV between farms using pelleted feed and those using LVSSF. It also included sensitivity analyses that related NPV and IRR to increased snakehead prices. Results demonstrated strong economic incentives for high-productivity farms to use pelleted feed. However, pelleted feed was too expensive for medium- and low-productivity farms. NPVs were more sensitive to reductions in the cost of pelleted feed than to increases in the cost of LVSSF or the cost of capital.     

Feasibility of Pond Production of Largemouth Bass,Micropterus salmoides,for a Filet Market

The effects of stocking density on food‐size largemouth bass (LMB), Micropterus salmoides, production (>0.5 kg) were evaluated in a 2‐yr study by stocking LMB fingerlings (mean weight = 57 g/fish) in 0.1‐ha earthen ponds at rates of 6175, 12,350, or 18,525 fish/ha. Gross yields increased from 3989 to 9096 kg/ha as stocking density increased. No significant differences were observed in survival rates (range of 65–74%) due to density. Maximum feed consumption occurred at water temperatures of 27–30 C. Feed conversion ratio (FCR) and mean harvest weight were significantly different (P < 0.05) among densities, with the lowest FCR and the lowest mean weight found at the highest density (18,525 fish/ha). At harvest, LMB were considered to be in good condition with relative weight (W_r) values of 123–124. Dressout yield percentages were 61–62% for whole‐dressed LMB and 34–35% for shank filets. LMB grew well and reached a size adequate for targeted shank filet sizes. However, the production costs of $7.26–$9.34/kg mean that LMB production for a filet market is unlikely to be feasible. Research to lower LMB fingerling and feed costs and improved FCR would contribute to improved economic feasibility.     

The U.S. Wholesale Market for Marine Ornamentals

The market for marine ornamentals encompasses all live marine species (fish and invertebrates) destined for the aquarium trade. In 1998, U.S. imports and exports were valued at approximately US $1.5 billion at the border (all dollar values cited in this paper are $US). In Florida, cultured freshwater and collected saltwater species accounted for $70 million and $4 million, respectively, in annual dockside revenue. To help explain Florida's marine landings and provide suggestions for future resource management and market campaigns that reflect the perceptions of the industry, a survey of wholesalers was initiated in 1999. Preliminary results indicate that there are several intermediate wholesale markets. Florida firms are closer to the supply as many also collect. Wholesalers in other states handle more freshwater product, are larger, and tend to import a larger share of their inventory. Consolidation is expected to continue, but niche markets for eco-friendly firms are expected to grow. In Florida, marketing strategies should focus on the observed higher survival rates and increasing supply of the popular invertebrate species. Many wholesalers are concerned about additional regulations that could reduce the number of collectors and thereby increase supply variability, a noted weakness of the Florida industry.     

Detection and quantification of Aeromonas schubertii in Channa maculata by TaqMan MGB probe fluorescence real‐time quantitative PCR

Aeromonas schubertii is a major epidemiological agent that threatens cultured snakeheads (Channidae) and has caused great economic losses in fish‐farming industries in China in recent years. In present study, a specific TaqMan minor groove binder (MGB) probe fluorescence real‐time quantitative PCR (qPCR) assay was developed to rapidly detect and quantify A. schubertii. A pair of qPCR primers and a TaqMan MGB probe were selected from the rpoD gene, which were shown to be specific for A. schubertii. A high correlation coefficient (R² = 0.9998) in a standard curve with a 103% efficiency was obtained. Moreover, the qPCR method's detection limit was as low as 18 copies/μl, which was 100 times more sensitive than that of conventional PCR. The detection results for the A. schubertii in pond water and fish tissue were consistent with those of the viable counts. Bacterial load changes detected by qPCR in different tissues of snakeheads infected with A. schubertii showed that the gills and intestines may be the entry for A. schubertii, and the spleen and kidney are major sites for A. schubertii replication. The established method in present study should be a useful tool for the early surveillance and quantitation of A. schubertii.     

BIOECONOMICS OF COBIA,RACHYCENTRON CANADUM,CULTURE IN VIETNAM

This article presents an analysis of the profitability and intensity of cobia culture by small-scale farmers in Vietnam, especially focusing on current feeding practices and perceptions regarding adoption of manufactured diets. Bioeconomic modelling is used so the interactions between biological and economic processes can be analyzed. Overall, it is found that cobia farming is moderately to highly profitable when compared to other aquaculture species in Vietnam. Culture practices and the level of intensity of cobia farming differ significantly across Vietnam. Initial stocking density, total number of fish stocked, number and size of cages, and quantity of feed used are all higher in southern Vietnam than the north. The higher level of intensification in the south leads to significantly higher total costs, productivity and profitability. The dominant cost source is feed, which is predominantly low-value fish. To capture the environmental and potential economic benefits of adopting pelleted diets, then negative farmer perceptions regarding relatively slow growth rates, and lack of availability compared with low-value fish need to be overcome.     

Linkages and Trust in the Value Chain for Small‐scale Aquaculture in Asia

The small‐scale aquaculture (SSA) sector is recognized as making an important contribution to food security, poverty alleviation, and socioeconomic development. A value chain analysis can uncover insights into the linkages and trust within a value chain and constraints and challenges that face the sector. This paper examines the linkages and trust between SSA producers and traders in Asia in order to better understand the constraints and opportunities faced by small‐scale producers. The perspective revealed by the value chain analysis provides response strategies that can enhance the sustainability and competitiveness of the entire value chain and the actors that comprise it.     

湖泊围养鱼类血液学指标的初步研究

本试验测定了185尾在湖泊围养区和池塘内体质健壮的草鱼、青鱼、团头鲂、鲢鱼、鳙鱼的血液,共取得红血球、血红蛋白、血糖、总蛋白、白蛋白、尿素氮、胆固醇、甘油三酯八项指标的1367个数据。经可靠性分析,除血糖指标的相对误差值略高于5％外,其余各项血液指标均值的相对误差,均达到生物调查实验要求。     

Evaluation of Reduced Fish Meal Diets for Second Year Growout of the Largemouth Bass,Micropterus salmoides

Development of efficient cost‐effective diets is a critical component in the refinement of production technologies for the largemouth bass, Micropterus salmoides (LMB). One of the first steps in reducing feed costs can be to decrease the amount of fish meal in the diet. The objective of this study was to evaluate reduced levels of fish meal, and a least‐cost formulation diet, for second year growout of LMB under practical pond conditions. Twelve 0.04‐ha ponds were stocked with juvenile LMB (210.1 ± 3.3 g) at a stocking density of 8650 fish/ha (350 fish/pond). Each pond was randomly assigned one of the four dietary treatments with three replicate ponds per treatment. The three experimental diets contained varying levels of fish meal. Diets FM‐45, FM‐24, and FM‐8 contained 45, 23.5, and 8% fish meal, respectively. In diets FM‐24 and FM‐8, fish meal was replaced by varying levels of poultry by‐product meal, soybean meal, and blood meal. The fourth diet was a commercial salmonid diet widely used as a LMB growout feed (Nelson and Sons, Inc., Silvercup ^TM , Steelhead, Murray, UT, USA). This diet served as a commercial control (CC) and contained 46% crude protein. The experimental diets were formulated to be isonitrogenous and isocaloric with the CC diet and were fed once daily to apparent satiation for 180 d. At harvest, there were no significant differences between treatments ( P > 0.05 ) in terms of survival, which averaged 95% overall. Mean weights of fish fed the three experimental diets FM‐45, FM‐24 and FM‐8 were not significantly different ( P > 0.05 ) and averaged 518, 546, and 529 g, respectively, but were all significantly greater ( P≤ 0.05 ) than those fed the CC (488 g). Feed conversion ratio (FCR) of fish fed the FM‐45 and FM‐8 diets (1.43 and 1.46, respectively) was significantly greater ( P≤ 0.05 ) than those fed the FM‐24 diet (1.34). The FCR of fish fed the CC diet (1.39) was not significantly different ( P > 0.05 ) from fish fed other diets. Feed cost per unit of weight gain ($US/kg) was significantly lower ( P≤ 0.05 ) in fish fed the FM‐24 and FM‐8 diets ($0.73 and $0.72/kg, respectively) than in fish fed other diets. Feed cost per unit gain of fish fed the FM‐45 diet ($0.83/kg) was significantly lower ( P≤ 0.05 ) than those fed the CC diet ($1.04/kg). There were no significant differences ( P > 0.05 ) in dress‐out percentages or proximate composition among fish fed the four diets. This study indicates that fish meal levels in feeds used for the second year growout of LMB can be reduced to ≥ 8% of the formulation without reducing survival or growth and without negatively impacting body composition.     

细鳞鱼全人工繁育技术的研究

从乌苏里江、牡丹江中采捕野生细鳞鱼（Brachymystax lenok）亲鱼,暂养后催产获得的鱼苗饲养在黑龙江水产研究所渤海冷水性鱼类试验站,观察和测定了水温2～18℃下人工养殖的细鳞鱼的生长和发育,自2003～2010年连续进行了人工繁殖和苗种培育。结果表明,在流水池塘养殖条件下,投喂人工配合颗粒饲料,可使细鳞鱼正常生长和性腺发育成熟,人工催产方式可以批量获得鱼苗,且生长速度、产卵量、发眼率与野生细鳞鱼无显著差异。     

Pond culture of snakehead in Hong Kong: a case study of an economic solution to common resources

This article records the trade practice and culture cycle of Ophiocephalus maculatus (snakeheads) as adopted by a fish farm at Ngau Tam Mei, the New Territories, Hong Kong. This farm is one of the few remaining local enterprises that have the skills to spawn this labyrinth fish. Documentation is timely not only because there has been great demand for the transfer of culture technology (spawning) to China, but also because the species may become extinct with the demise of the culture business through urbanization. The discussion throws light on the effectiveness and limitations of the institutions of private rights as a means of conserving common resources.