Should only females of giant freshwater prawn Macrobrachium rosenbergii be selected in genetic improvement programmes?

Sexual dimorphism is widely observed in almost all farmed aquatic animal species but giant freshwater pawn (GFP) is unique, with males characterized by three main morphotypes (blue claw, orange claw and small males) and females by different reproduction status (ovary, berried egg and already‐spawned females). There has been reported evidence that the effect of male morphotype may have masked genetic variation in growth‐related traits, as a result the heritability for male body weight was lower than that estimated in female. A pending question has arisen whether selection should be made in female only. To answer this question, we used an 8‐year data set from a long‐term selection programme (2008–2015) for high growth in this species comprising 106,756 individuals that were offspring of 515 sires and 810 dams. The body weight data of female and male GFP or of each morphotype was treated as a separate trait and a multi‐trait approach was used to estimate genetic correlations for homologous traits between sexes and between morphotypes. Our analysis showed that there were little differences in the heritability estimates between female and male. In female, mature ovary individual displayed higher heritability than berried egg and already‐spawned females. For male, the heritability for blue claw, orange claw and small males were 0.11, 0.06 and 0.00 respectively. Between‐sex genetic correlation was moderate (0.55 ± 0.11) for body weight, suggesting that the trait expressions in female and male may be genetically different. In female, the genetic correlations for body weight among three female types were close to one (0.91–0.94). In contrast, the genetic correlations for body weight between male morphotypes especially between blue claw or orange claw and small males were low (0.15–0.25). Furthermore, we estimated genetic gain as the difference in least square means (LSM) or estimated breeding values (EBV) between the selection line and control group. The genetic gain in body weight was smaller in females than in males. It is concluded that there is no need to run separate breeding programme for female and male GFP. A combined selection using both female and male data can achieve selection response for body weight as demonstrated in the present study.     

Data envelopment analysis for production efficiency improvement: An empirical application on brine shrimp Artemia franciscana culture in the Mekong Delta,Vietnam

Artemia culture in the Mekong Delta, Vietnam, is becoming more and more important to satisfy the global demands of cyst production. Nevertheless, Artemia cyst productivity in the Mekong Delta has been fluctuating largely due to not only technical inefficiencies and external factors but also farms’ characteristics. This study employed a data envelopment analysis to evaluate the production efficiencies in correlation with biological and cost inputs of Artemia culture in Vinh Chau and Bac Lieu located in the Mekong Delta. The key factors affecting technical efficiency (TE) were determined using ordinary least squares regression model. The empirical results indicated that production efficiencies of farms in Vinh Chau and Bac Lieu were similar with metatechnology ratios of 0.97 and 0.96 respectively. About 62.8% of surveyed farms were operating in technically inefficient circumstances. Farmers’ experience, educational level and culture technique training participation had positive effects on TE, while climate effects and water problems have been proved to have negative effects on TE. To improve production efficiency, inefficient farms are suggested to have moderately increasing combinations of organic fertilizer, chemical and feed. The use of probiotics should be reduced as it increases production cost and affects TE. Notably, a collaboration of scientists and feed processing companies is recommended to produce a specific formulated feed for Artemia in commercial scales. This study also proposes adaptive policies for local governments and cooperatives to assist coastal famers in the Mekong Delta overcome technical inefficiencies, improve cyst productivity and obtain economic sustainability in Artemia culture.     

The potential of informal institutions for marine fisheries management—A case study of a coastal commune in Vietnam

The potential of informal institutions for sustainable management of marine fisheries was examined. The study is based on both primary data collected through two group discussions and interviews and secondary information, including material related to fishing gear operation and whale worship. It shows that informal institutions, including fisher groups, fishing community norms, fisher's knowledge and whale worship have potential to strengthen institutional, ecological, social and community aspects of sustainable fisheries development. Although these informal institutions are not able to fix completely all the problems faced by formal institutions, they are able to complement and consolidate formal institutions to manage marine fisheries effectively. The findings of this study suggest it is imperative that formal institutions should be improved simultaneously with informal institutions to enhance current management for sustainable marine fisheries development.     

Development of a continuous cell line from larval Atlantic cod (Gadus morhua) and its use in the study of the microsporidian,Loma morhua

In vitro cell culture methods are crucial for the isolation, purification and mass propagation of intracellular pathogens of aquatic organisms. Cell culture infection models can yield insights into infection mechanisms, aid in developing methods for disease mitigation and prevention, and inform commercial‐scale cultivation approaches. This study details the establishment of a larval cell line (GML‐5) from the Atlantic cod (Gadus morhua) and its use in the study of microsporidia. GML‐5 has survived over 100 passages in 8 years of culture. The line remains active and viable between 8 and 21°C in Leibovitz‐15 (L‐15) media with 10% foetal bovine serum and exhibits a myofibroblast phenotype as indicated by immuno‐positive results for vimentin, α‐smooth muscle actin, collagen I and S‐100 proteins, while being desmin‐negative. GML‐5 supports the infection and development of two microsporidian parasites, an opportunistic generalist (Anncaliia algerae) and cod‐specific Loma morhua. Using GML‐5, spore germination and proliferation of L. morhua was found to require exposure to basic pH and cool incubation temperatures (8°C), in contrast to A. algerae, which required no cultural modifications. Loma morhua‐associated xenoma‐like structures were observed 2 weeks postexposure. This in vitro infection model may serve as a valuable tool for cod parasitology and aquaculture research.     

Can fermented soybean meal and squid by‐product blend be used as fishmeal replacements for Japanese flounder (Paralichthys olivaceus)?

An experiment was carried out to evaluate fermented soybean meal and squid by‐product blend (1:1) (FP) as replacement of fishmeal (FM) for Japanese flounder, Paralichthys olivaceus. Five isocaloric (19 kJ g^?1) diets were prepared by replacing 0 (FP0), 12 (FP12), 24 (FP24), 36 (FP36) and 48% (FP48) FM protein with FP. Triplicate groups of juveniles (mean weight of 3.9 g) were delivered the test diets for 8 weeks in a flow‐through sea water system. The results showed that there were no significant differences (P > 0.05) among the growth rates of fish fed FP0, FP12, FP24 and FP36 diets. Growth and nutrient utilization parameters were significantly reduced in fish fed FP48 diet. Although, whole body proximate composition of fish were not significantly affected by the dietary treatments compared to the control; methionine and phenylalanine contents were significantly decreased in FP48 group. Protein retention was also significantly decreased in the similar group of fish. Dietary treatments did not alter most of the plasma metabolites, while some of the health parameters were improved in the replacement groups. Results suggested that FP is a potential candidate for alternative protein ingredient in aquafeed and can replace 36% FM protein in the diet of Japanese flounder.     

Quantifying growth in maricultured corals using photogrammetry

In coral mariculture, growth is one of the most common ways to track success. However, numerous methods of monitoring coral growth make comparative studies challenging. A literature review of 39 studies from 1982 to 2017 indicated that the most predominant non‐invasive methods used were linear and areal measurement and these were evaluated for their accuracy using nursery‐reared corals. The monthly change in linear and areal growth rates of six coral species (n = 215), Pocillopora acuta, Hydnophora rigida, Merulina ampliata, Podabacia crustacea, Echinopora lamellosa and Platygyra sinensis were measured via photogrammetry. We tested whether the planar area of coral colonies can be estimated using three geometric formulas of linear measurements. Based on the literature review, the six types of measurement methods were namely linear, volume, weight, area, count of polyps/branches and calcification, in decreasing order of application. Our results showed that the change in area calculated by geometric mean diameter (GMD) formulas provided the most accurate estimation among the three formulas and was strongly correlated with planar area (R² ≥ .60; p < .05) for all coral species, except E. lamellosa and Pl. sinensis. However, our findings suggest that it is not ideal to use geometric formulas to estimate the change in area. Instead, we posit that areal photogrammetry represents the simplest yet accurate non‐invasive method for rapid monitoring of extensive areas of corals in situ. Lastly, we discuss the recommendations and limitations for areal photogrammetry.     

Economic feasibility of recirculating aquaculture systems in pangasius farming

This study aims to analyze the economic feasibility of recirculating aquaculture systems (RAS) in pangasius farming in Vietnam. The study uses a capital budgeting approach and accounts for uncertainty in key parameters. Stochastic simulation is used to simulate the economic performance of medium and large farms operating with a traditional system or RAS. Data are obtained through structured surveys and a workshop in the Mekong River Delta. Results show that for large farms, net present value increases from an average of 589,000 USD/ha to 916,000 USD/ha after implementing RAS. Overall, the probability that RAS is a profitable investment is found to be 99% for both farm sizes. With RAS, the crucial parameters determining profitability are price, yield, costs of fingerling, feed, and initial investment. Findings on the robustness of the economic performance of RAS are useful to support public and private decision making towards increasing the sustainability of pangasius production.     

Assessment of household risk management strategies for coastal aquaculture: the case of clam farming in Thaibinh Province,Vietnam

Clam farmers have experienced different types of risks that have been further exacerbated by the rapid expansion of clam farming areas, increased growing densities, and increased market difficulties in recent years in the Thaibinh Province of Vietnam. Most farmers have been seriously affected by production risk, market risk, and financial risk, while a number of others have met with success in almost all of their clam-raising cycles. This study applied a differentiating comparative analysis method and multiple discriminant analysis method to discuss the differences in risk management strategies between and among clam farming households and the impacts of those differences on their success/failure rates. In general, the tactics are related to increase in farm size, the application of technical innovations, diversifying livelihood activities, and accessing secure financial sources all provided better conditions for clam growth, diminished losses, and led to speedier recovery from shocks. To support farmers in managing risks, several government interventions are needed: (1) better re-zoning of clam farming areas in parallel with an increase in the farm size of each household, (2) promoting sustainable linkages between the farmers and the formal financial market and output market, and (3) investing more funding into research and extension related to sustainable clam farming practices and to the improvement of farmers’ skills in cooperative works and management.     

Effect of <Emphasis Type="Italic">Lactococcus lactis</Emphasis> K-C2 on the growth performance,amino acid content and gut microflora of amberjack <Emphasis Type="Italic">Seriola dumerili</Emphasis>

This study aimed to evaluate the effect of Lactococcus lactis K-C2 on the growth performance, microbial diversity, and release of free amino acids in the intestinal tract and the edible parts of young amberjack, Seriola dumerili. Fish were fed a diet with or without strain K-C2 (2?×?10¹⁰ cfu/g feed) for 25 days. The results indicated that the growth performance of fish in the treated group was significantly higher than those in the control group (p?<?0.05). The amount of five amino acids (aspartate, sarcosine, taurine, alanine, and arginine) in the gut content and 13 of 21 amino acids in the edible parts of fish in the treated group were significantly higher (p?<?0.05) than those in the control group. Sphingomonas, Propionibacterium, and Mycobacterium were observed in gut microflora of fish in both the control and treated groups. Staphylococcus and Kocuria were detected in one sample from the control and treated groups; Acinetobacter and Acidobacteria were found in one sample from the control group. L. lactis was only found in one sample in the treated group. In conclusion, the dietary administration of probiotic L. lactis stimulated growth, reduced feed consumption, and improved the nutritional value of cultured amberjack.