In the 40 years since the essentiality of polyunsaturated fatty acids (PUFA) in fish was first established by determining quantitative requirements for 18:3n − 3 and 18:2n − 6 in rainbow trout, essential fatty acid (EFA) research has gone through distinct phases. For 20 years the focus was primarily on determining qualitative and quantitative EFA requirements of fish species. Nutritional and biochemical studies showed major differences between fish species based on whether C PUFA or long-chain (LC)-PUFA were required to satisfy requirements. In contrast, in the last 20 years, research emphasis shifted to determining “optimal” levels of EFA to support growth of fish fed diets with increased lipid content and where growth expectations were much higher. This required greater knowledge of the roles and functions of EFA in metabolism and physiology, and how these impacted on fish health and disease. Requirement studies were more focused on early life stages, in particular larval marine fish, defining not only levels, but also balances between different EFAs. Finally, a major driver in the last 10–15 years has been the unavoidable replacement of fish oil and fishmeal in feeds and the impacts that this can have on n − 3 LC-PUFA contents of diets and farmed fish, and the human consumer. Thus, dietary n − 3 in fish feeds can be defined by three levels. Firstly, the minimum level required to satisfy EFA requirements and thus prevent nutritional pathologies. This level is relatively small and easy to supply even with today's current high demand for fish oil. The second level is that required to sustain maximum growth and optimum health in fish being fed modern high-energy diets. The balance between different PUFA and LC-PUFA is important and defining them is more challenging, and so ideal levels and balances are still not well understood, particularly in relation to fish health. The third level is currently driving much research; how can we supply sufficient n − 3 LC-PUFA to maintain these nutrients in farmed fish at similar or higher levels than in wild fish? This level far exceeds the biological requirements of the fish itself and to satisfy it we require entirely new sources of n − 3 LC-PUFA. We cannot rely on the finite and limited marine resources that we can sustainably harvest or efficiently recycle. We need to produce n − 3 LC-PUFA and all possible options should be considered.
Aquaculture is the main source to increase fish supply. Fast development of aquaculture and increasing fish demand lead to intensification of fish culture, magnifying stressors for fish and thus heightening the risk of disease. Until now, chemotherapy has been widely used to prevent and treat disease outbreaks, although use of chemical drugs has multiple negative impacts on environment and human health e.g. resistant bacterial strains and residual accumulation in tissue. Hence, disease management in aquaculture should concentrate on environmentally friendly and lasting methods. Recently, increasing attention is being paid to the use of plant products for disease control in aquaculture as an alternative to chemical treatments. Plant products have been reported to stimulate appetite and promote weight gain, to act as immunostimulant and to have antibacterial and anti-parasitic (virus, protozoans, monogeneans) properties in fish and shellfish aquaculture due to active molecules such as alkaloids, terpenoids, saponins and flavonoids. However, as it is a relatively emerging practice there is still little knowledge on the long-term effects of plant extracts on fish physiology as well as a lack of homogenization in the extract preparation and fish administration of the plant extracts. This article aims to review the studies carried out on the use of plant products on fish aquaculture and their biological effects on fish such as growth promoter, immunostimulant, antibacterial and anti-parasitic. It also intends to evaluate the current state of the art, the methods used and the problems encountered in their application to the aquaculture industry.
The demand for cultured carp species has grown tremendously during the last decade due to their high market value. Recently, intensive aquaculture system has been expanding and is emerging as one of the most practical and promising tools to meet the requirements of carp. However, in intensive fish farming, animals are subjected to stress conditions that weaken fish immune systems, leading to increased susceptibility to diseases. These diseases have resulted in production losses and remain as one of the major causes of concern for carp farmers. Recently, one of the major limiting factors in intensive fish culture is the use of dietary supplements probiotics and prebiotics. These natural ingredients enhance the immune response of fish, confer tolerance against different stressors and minimize the risk associated with the use of chemical products such as: vaccines, antibiotics and chemotherapeutics. The present review summarizes and discusses the results of probiotic and prebiotic administration on growth performance, gut physiology, intestinal microbiota, immune response and health status of different carp species. Furthermore, this study tries to cover the gaps in existing knowledge and suggest issues that merit further investigations.
In 1990, 90% of the ingredients in Norwegian salmon feed were of marine origin, whereas in 2013 only around 30%. The contents of fish meal and fish oil in the salmon feed were 18% and 11%, respectively, in 2013. Between 2010 and 2013, salmon production in Norway increased by 30%, but due to a lower inclusion of marine ingredients in the diet, the total amount of marine ingredients used for salmon feed production was reduced from 544,000 to 466,000 tonnes. Norwegian salmon farming consumed 1.63 million tonnes of feed ingredients in 2012, containing close to 40 million GJ of energy, 580,000 tonnes of protein and 530,000 tonnes of lipid. 1.26 million tonnes of salmon was produced. Assuming an edible yield of 65%, 820,000 tonnes of salmon fillet, containing 9.44 million GJ, and 156,000 tonnes of protein were produced. The retentions of protein and energy in the edible product in 2012 were 27% and 24%, respectively. Of the 43,000 tonnes of EPA and DHA in the salmon feed in 2012, around 11,000 tonnes were retained in the edible part of salmon. The retentions of EPA and DHA were 46% in whole salmon and 26% in fillets, respectively. The / (FIFO) measures the amount of fish meal and fish oil that is used to produce one weight equivalent of farmed fish back to wild fish weight equivalents, and the (FFDR) is the amount of wild caught fish used to produce the amount of fish meal and fish oil required to produce 1 kg of salmon. From 1990 to 2013, the forage fish dependency ratio for fish meal decreased from 4.4 to 0.7 in Norwegian salmon farming. However, weight-to-weight ratios such as FIFO and FFDR do not account for the different nutrient contents in the salmon product and in the forage fish used for fish meal and fish oil production. express the amount of marine oil and protein required to produce 1 kg of salmon oil and protein. In 2013, 0.7 kg of marine protein was used to produce 1 kg of salmon protein, so the Norwegian farmed salmon is thus a net producer of marine protein. This manuscript shows the retention efficiency of nutrients from feed resources to final product in the Norwegian salmon production, including limiting resources such as the omega-3 fatty acids EPA and DHA and phosphorous. It is highly relevant to compare the efficiency in commercial scale with experimental data, and this is to our knowledge the first attempt to make such calculations for an entire commercial aquaculture production.
The finfish and crustacean aquaculture sector is still highly dependent upon marine capture fisheries for sourcing key dietary nutrient inputs, including fish meal and fish oil. This dependency is particularly strong within compound aquafeeds for farmed carnivorous finfish species and marine shrimp. Results are presented concerning the responses received from a global survey conducted between December 2006 and October 2007 concerning the use of fish meal and fish oil within compound aquafeeds using a questionnaire sent to over 800 feed manufacturers, farmers, researchers, fishery specialists, and other stakeholders in over 50 countries. On the basis of the responses received, it is estimated that in 2006 the aquaculture sector consumed 3724 thousand tonnes of fish meal (68.2% total global fish meal production in 2006) and 835 thousand tonnes of fish oil (88.5% total reported fish oil production in 2006), or the equivalent of 16.6 million tonnes of small pelagic forage fish (using a wet fish to fish meal processing yield of 22.5% and wet fish to fish oil processing yield of 5%) with an overall fish-in fish-out ratio of 0.70. At a species-group level, calculation of small pelagic forage fish input per unit of farmed fish or crustacean output showed steadily decreasing fish-in fish-out ratios for all cultivated species from 1995 to 2006, with decreases being most dramatic for carnivorous fish species such as salmon (decreasing from 7.5 to 4.9 from 1995 to 2006), trout (decreasing from 6.0 to 3.4), eel (decreasing from 5.2 to 3.5), marine fish (decreasing from 3.0 to 2.2) and to a lesser extent shrimp (decreasing by 1.9 to 1.4 from 1995 to 2006. Net fish producing species in 2006 (with fish-in fish-out ratios below 1), included herbivorous and omnivorous finfish and crustacean species, including non-filter feeding Chinese carp (0.2), milkfish (0.2), tilapia (0.4), catfish (0.5), and freshwater crustaceans (0.6). On the basis of increasing global fish meal and fish oil costs, it is predicted that dietary fish meal and fish oil inclusion levels within compound aquafeeds will decrease in the long term, with fish meal and fish oil usage increasingly being targeted for use as a high value specialty feed ingredient for use within higher value starter, finisher and broodstock feeds, and by so doing extending supply of these much sought after and limited feed ingredient commodities.
Several shrimp diseases are new or newly emerged in Asia, including acute hepatopancreatic necrosis disease (AHPND), hepatopancreatic microsporidiosis (HPM), hepatopancreatic haplosporidiosis (HPH), aggregated transformed microvilli (ATM) and covert mortality disease (CMD). In addition to these, white spot disease (WSD), yellow head disease (YHD) and infectious myonecrosis (IMN) continue as the most serious viral threats to shrimp farmers in the region. Other diseases such as monodon slow growth syndrome (MSGS), white tail disease (WTD) and abdominal segment deformity disease (ASDD) are of less concern. In contrast, Taura syndrome virus (TSV) and infectious hypodermal and hematopoietic necrosis virus (IHHNV) have become innocuous due to the widespread use of highly tolerant specific pathogen free (SPF) stocks of ( ) that dominate production. Similarly, diseases caused by monodon baculovirus (MBV) and hepatopancreatic parvovirus (HPV) appear not to affect . Spread of diseases has been promoted by the use of live or fresh broodstock feeds such as polychaetes and clams. Also, shortages in the supply of imported SPF broodstock led some entrepreneurs to employ post larvae (PL) of imported SPF stocks to produce 2nd generation broodstock in open shrimp ponds where they became contaminated and were then used to produce PL for stocking ponds. These practices left the whole shrimp industry vulnerable to rapid spread of the new and newly emerging diseases and resulted in the current crisis in Asian shrimp culture. The situation has been exacerbated since 2009 by an almost exclusive focus on AHPND, which is only partially responsible for what has been widely called early mortality syndrome (EMS). The purpose of this review is to summarize progress of research on AHPND bacteria and also to encourage a wider focus on additional pathogens that are causing farm losses. The significance of these diseases and their implications for the future of shrimp aquaculture are discussed. This review summarizes recent information about new and newly emerging diseases of cultured shrimp in Asia and discusses the biosecurity lapses that led to the current shrimp production crisis. All industry stakeholders must be aware of this situation and of the need for regional and global collaborative efforts to stem this crisis and prevent future development of another.
Salmonids are an important contributor to fish production in many countries. Concerted research efforts have concentrated on optimising production with eco-friendly alternatives to the therapeutic use of antimicrobials. Probiotics and prebiotics offer potential alternatives by providing benefits to the host primarily via the direct or indirect modulation of the gut microbiota. Suggested modes of action resulting from increased favourable bacteria (e.g. lactic acid bacteria and certain spp.) in the gastrointestinal (GI) tract include the production of inhibitory compounds, competition with potential pathogens, inhibition of virulence gene expression, enhancing the immune response, improved gastric morphology and aiding digestive function. The application of probiotics and prebiotics may therefore result in elevated health status, improved disease resistance, growth performance, body composition, reduced malformations and improved gut morphology and microbial balance. Current research demonstrates successful proof of these concepts and a foundation for applications in salmonid aquaculture. However, application strategies applied in current studies are varied and often impractical at industrial level farming; thus, it is difficult to plan an effective feeding strategy for commercial level applications. Future studies should focus on providing practical industrial scale applications. Additionally, from a scientific perspective we must have a better understanding of the mucosal–bacterial interactions which mediate the host benefits in order to achieve optimal utilisation.
Aquaculture is the fastest growing food production industry, and the vast majority of aquaculture products are derived from Asia. The quantity of aquaculture products directly consumed is now greater than that resulting from conventional fisheries. The nutritional value of aquatic products compares favourably with meat from farm animals because they are rich in micronutrients and contain high levels of healthy omega-3 fatty acids. Compared with farm animals, fish are more efficient converters of energy and protein. If the aquaculture sector continues to expand at its current rate, production will reach 132 million tonnes of fish and shellfish and 43 million tonnes of seaweed in 2020. Future potential for marine aquaculture production can be estimated based on the length of coastline, and for freshwater aquaculture from available land area in different countries. The average marine production in 2005 was 103 tonnes per km coastline, varying from 0 to 1721 (China). Freshwater aquaculture production in 2005 averaged 0.17 tonnes/ha, varying from 0 to close to 6 tonnes per ha (Bangladesh), also indicating potential to dramatically increase freshwater aquaculture output. Simple estimations indicate potential for a 20-fold increase in world aquaculture production. Limits imposed by the availability of feed resources would be lessened by growing more herbivorous species and by using more of genetically improved stocks. Aquaculture generally trails far behind plant and farm animal industries in utilizing selective breeding as a tool to improve the biological efficiency of production. It is estimated that at present less than 10% of aquaculture production is based on genetically improved stocks, despite the fact that annual genetic gains reported for aquatic species are substantially higher than that of farm animals. With an average genetic gain in growth rate of 12.5% per generation, production may be dramatically increased if genetically improved animals are used. Importantly, animals selected for faster growth have also been shown to have improved feed conversion and higher survival, implying that increased use of selectively bred stocks leads to better utilization of limited resources such as feed, labour, water, and available land and sea areas. ► We demonstrate existence of vast potential for increased aquaculture production. ► The largest potential for aquaculture lies in the marine environment. ► Selection responses in aquaculture species are higher than for conventional livestock. ► More use of genetically improved stocks may dramatically increase aquaculture output. ► Genetically improved stocks are critical for better utilization of limited resources.
The World Wildlife Fund is facilitating a dialogue on impacts of salmon aquaculture. The goal of the dialogue is to establish the state of knowledge in seven subject areas associated with the industry: benthic impacts, nutrient loading, escapees, chemical inputs, diseases, feeds and social issues and to establish international standards for salmon aquaculture practices. Chemical inputs from salmon aquaculture include antifoulants, antibiotics, parasiticides, anaesthetics and disinfectants. The use and potential effects of these compounds are herein summarized for the four major salmon producing nations: Norway, Chile, UK and Canada. Regulations governing chemical use in each country are presented as are the quantities and types of compounds used. The problems associated with fish culture are similar in all jurisdictions, the magnitude of problems is not and the number of compounds available to the fish farmer varies from country to country. Unfortunately, the requirement to publically report chemical use is inconsistent among countries. Chemical use data are available from Norway, Scotland and parts of Canada. The government of Chile and some Canadian provinces, while requiring that farmers report disease occurrence, compounds prescribed and quantities used, do not make this information readily available to the public. The fact that these data are available from regulatory agencies in Scotland and Norway adds pressure for other jurisdictions to follow suit. Data such as these are essential to planning and conducting research in field situations.
Probiotics, which are regarded as micro-organisms administered orally leading to health benefits, are used extensively in aquaculture for disease control, notably against bacterial diseases. In contrast to use with terrestrial animals where lactic-acid producing bacteria dominate, a diverse range of micro-organisms including Gram-negative and Gram-positive bacteria have been considered in aquaculture. The source of these organisms is often the digestive tract of the host animal. The mode of action includes competitive exclusion and immunomodulation. Probiotics may also improve appetite and lead to enhanced growth and better feed conversion.
As the human population continues to grow, food production industries such as aquaculture will need to expand as well. In order to preserve the environment and the natural resources, this expansion will need to take place in a sustainable way. Biofloc technology is a technique of enhancing water quality in aquaculture through balancing carbon and nitrogen in the system. The technology has recently gained attention as a sustainable method to control water quality, with the added value of producing proteinaceous feed In this review, we will discuss the beneficial effects of the technology and identify some challenges for future research. ► Biofloc technology aims at enhancing water quality through balancing C and N. ► Heterotrophic bacteria assimilate inorganic N waste into biomass. ► The bioflocs can be used as proteinaceous feed for the cultured animals. ► We discuss advantages of biofloc technology and challenges for further research.
Medicinal plants have been known as immunostimulants for thousands of years. The application of medicinal plants as natural and innocuous compounds has potential in aquaculture as an alternative to antibiotics and immunoprophylactics. The growing interest in these plants has increased world-wide because they are easy to prepare, cheap, and have few side effects on animals and the environment. A wide range of medicinal plants such as herbs, spices, seaweeds, herbal medicines, herbal extracted compounds, traditional Chinese medicines, and commercial plant-derived products has been studied in various aquatic animals. The whole plant or its parts viz. roots, leaves, seeds, flowers or extract compounds can be used. The extraction process is simple, with ethanol and methanol being commonly used. Various chemicals used to extract compounds may lead to different degrees of effects on aquatic animals. Application methods can be either single or in combination, or even in a mixture with other immunostimulants, via water routine or feed additives and enrichment, where single administrations are as practical as combinations. The dosages and duration of time varies and the optimal levels have not been considered. Medicinal plants show their main properties as growth promoters, immune enhancers, where they act as antibacterial and antiviral agents to the host immune system. Unfortunately, the mechanisms are not fully understood. Therefore, most authors did not recommend that their results be used directly, while suggestions are proposed for further investigations.
Gut microbes are key players in host immune system priming, protection and development, as well as providing nutrients to the host that would be otherwise unavailable. Due to this importance, studies investigating the link between host and microbe are being initiated in farmed fish. The establishment, maintenance and subsequent changes of the intestinal microbiota are central to define fish physiology and nutrition in the future. In fish, unlike mammals, acquiring intestinal microbes is believed to occur around the time of first feeding mainly from the water surrounding them and their microbial composition over time is shaped therefore by their habitat. Here we compare the distal intestine microbiota of Atlantic salmon parr reared in a recirculating laboratory aquarium with that of age matched parr maintained in cage culture in an open freshwater loch environment of a commercial fish farm to establish the microbial profiles in the gut at the freshwater stage and investigate if there is a stable subset of bacteria present regardless of habitat type. We used deep sequencing across two variable regions of the 16S rRNA gene, with a mean read depth of 180,144 ± 12,096 raw sequences per sample. All individual fish used in this study had a minimum of 30,000 quality controlled reads, corresponding to an average of 342 ± 19 Operational Taxonomic Units (OTUs) per sample, which predominantly mapped to the phyla , , and . The results indicate that species richness is comparable between both treatment groups, however, significant differences were found in the compositions of the gut microbiota between the rearing groups. Furthermore, a core microbiota of 19 OTUs was identified, shared by all samples regardless of treatment group, mainly consisting of members of the phyla , and . Core microbiotas of the individual rearing groups were determined (aquarium fish: 19 + 4 (total 23) OTUs, loch fish: 19 + 13 (total 32) OTUs), indicating that microbe acquisition or loss is occurring differently in the two habitats, but also that selective forces are acting within the host, offering niches to specific bacterial taxa. The new information gathered in this study by the Illumina MiSeq approach will be useful to understand and define the gut microbiota of healthy Atlantic salmon in freshwater and expand on previous studies using DGGE, TGGE and T-RFPL. Monitoring deviations from these profiles, especially the core microbes which are present regardless of habitat type, might be used in the future as early indicator for intestinal health issues caused by sub optimal feed or infectious diseases in the farm setting. The Microbiome is central to gut health, local immune function and nutrient up take. We have used deep sequencing approach to show differences in rearing conditions of Atlantic salmon. This work is of interest to aquaculture nutritionists.
Aquaculture is one of the fastest growing food-producing sectors around the world. Among various kinds of cultivated organisms many marine and freshwater finfish and shellfish species constitute an important industry with their production increasing every year. Recently due to intensive farming practices infectious diseases pose a major problem in aquaculture industry, causing heavy loss to farmers. A number of approaches have been made to control diseases including sanitary prophylaxis, disinfection, and chemotherapy with particular emphasis on the use of antibiotics. However, the application of antibiotics and chemicals in culture is often expensive and undesirable since it leads to antibiotic and chemical resistance and consumer reluctance. Therefore immunostimulants such as glucan, chitin, lactoferrin, levamisole, and some medicinal plant extracts or products have been used to control fish and shellfish diseases. In this regard the medicinal plant extracts and their products act as immunostimulants modulating the immune response to prevent and control fish and shellfish diseases. The immunostimulants mainly facilitate the function of phagocytic cells, increase their bactericidal activities, and stimulate the natural killer cells, complement, lysozyme activity, and antibody responses in fish and shellfish which confer enhanced protection from infectious diseases. Currently increased consumer demand for perfection in fish and shellfish farms has put new dimensions to the quality, safety, elimination of concomitant pollutants, antibiotics, and carcinogens during the production process. In this context plants or their byproducts are preferred since they contain several phenolic, polyphenolic, alkaloid, quinone, terpenoid, lectine, and polypeptide compounds many of which have been shown to be very effective alternatives to antibiotics, chemicals, vaccines, and other synthetic compounds. In aquaculture the herbal medicines are also known to exhibit anti-microbial activity, facilitate growth, and maturation of cultured species; besides under intensive farming the anti-stress characteristics of herbs will be of immense use without posing any environmental hazard. Administration of herbal extracts or their products at various concentrations through oral (diet) or injection route enhance the innate and adaptive immune response of different freshwater and marine fish and shellfish against bacterial, viral, and parasitic diseases. Even an overdose of immunostimulants may induce immunosuppression without side effects but helps to reduce the losses caused by disease in aquaculture. The present review describes the role of medicinal herbs and their products on innate and adaptive immune response of finfish and shellfish.
The fish gut microbiota contributes to digestion and can affect the nutrition, growth, reproduction, overall population dynamics and vulnerability of the host fish to disease; therefore, this microbial community is highly relevant for aquaculture practice. Recent advances in DNA sequencing technologies and bioinformatic analysis have allowed us to develop a broader understanding of the complex microbial communities associated with various habitats, including the fish gut microbiota. These recent advances have substantially improved our knowledge of bacterial community profiles in the fish intestinal microbiota in response to a variety of factors affecting the host, including variations in temperature, salinity, developmental stage, digestive physiology and feeding strategy. The goal of this review is to highlight the potential of next-generation sequencing platforms for analysing fish gut microbiota. Recent and promising results in this field are presented along with a focus on new perspectives and future research directions of fish gut microbial ecology.
Due to the expansion of aquaculture and the limited resources available from the sea, it is necessary to find substitutes for fish meal for use in aquaculture. We believe that the use of insect meals as an alternative source of animal protein may be an option. To use insects for this purpose, it is necessary to determine the nutritive characteristics of these insects. To determinate the potential of insects as a substitute for fish meal in fish food used in aquaculture, we examined 16 different species, 5 of them as different stage of development, of the orders Coleoptera (4), Diptera (7) and Orthoptera (5). The insect analysed have a higher proportion of fat and less protein than fish meal. With the exceptions of histidine, threonine and lysine, the insects present an amino acid profile similar to fish meal, with Diptera b being the most similar group to fish meal. However, the fatty acid content of insects is very different from that of fish meal which is rich in n-3, especially 14% EPA, 16% DHA, practically absent in insects. The insects have higher ratios of omega 6 and monounsaturated fat.
The two-way interactions of aquaculture and the environment are diverse and complex. Three major questions are addressed: what happened in the past, what are today's trends, and what may the future hold? Traditional aquaculture is mostly environmentally compatible as it mainly uses on-farm and locally available wastes and by-products such as crop residues and animal or human manures for nutritional inputs or natural food in open water culture-based fisheries and mollusk and seaweed farming systems. Wastes, by-products and natural food were the only sources of nutritional inputs for most farmed aquatic organisms in the past before the relatively recent and increasing use of pelleted feed in modern aquaculture, leading to major environmental concerns. Environmental aspects of intensification of aquaculture and their relation to ecosystems and agro-ecosystems in inland terrestrial and aquatic, and coastal/offshore, land- and water-scapes are reviewed. Aquaculture is increasingly being adversely impacted by pollution from agricultural, domestic and industrial pollution. Environmental issues are illustrated by case studies of traditional and modern aquaculture farming practice in temperate and tropical inland and coastal areas. Promising technologies that employ the principles of traditional aquaculture to contribute to the sustainability of modern aquaculture are outlined. There does not appear to be a panacea for environmentally sustainable aquaculture on the horizon to meet the increasing demand for aquatic food. This is more likely to be met through improvements in existing technology, including combining aspects of traditional with modern practice; better management practices (BMPs); better site selection so that aquaculture remains within the carrying capacity of inland and coastal water bodies; and the most efficient use of land and water, which is more likely to be aquaculture than farming terrestrial crops in relatively poor agro-ecosystems. Inland aquaculture, especially in ponds, is likely to continue to dominate global aquatic food production.
The Thai Department of Fisheries (DOF), 2013 estimated that outbreaks of acute early mortality (often called early mortality syndrome or EMS) in cultivated shrimp were responsible for a 33% drop in shrimp production during the first quarter of 2013. Similar early mortality in Vietnam was ascribed to specific isolates of that caused acute hepatopancreatic necrosis disease (AHPND) but the status of EMS/AHPND in Thailand was unclear. Here we describe the isolation and characterization of bacteria isolated from the hepatopancreas (HP) of shrimp collected from an early mortality outbreak farm in Thailand. Four independent bacterial isolates were identified as by BLAST analysis and by gene-specific marker detection of a lecithin dependent hemolysin (LDH) considered to be specific for the species. Immersion challenges with 3 of these and a reference isolate, obtained from China in 2010, using a previously published laboratory infection model caused very high mortality accompanied by characteristic AHPND histopathology in the shrimp HP. Tests with one of these isolates (5HP) revealed that rate of mortality was dose dependent. Using the same challenge protocol, the 4th isolate (2HP) also caused high mortality, but it was not accompanied by AHPND histopathology. Instead, it caused a different histopathology of the HP including collapsed epithelia and unique vacuolization of embryonic cells (E-cells). These results revealed the possibility of diversity in isolates of that may cause early mortality in shrimp cultivation ponds. Genomic and episomic DNA of these isolates and isolates of that cause no disease need to be compared to better understand the molecular basis of bacterial virulence in AHPND.
Polyploids can be defined as organisms with one or more additional chromosome sets with respect to the number most frequently found in nature for a given species. Triploids, organisms with three sets of homologous chromosomes, are found spontaneously in both wild and cultured populations and can be easily induced in many commercially relevant species of fish and shellfish. The major consequence of triploidy is gonadal sterility, which is of advantage in the aquaculture of molluscs since it can result in superior growth. In fish, the induction of triploidy is mainly used to avoid problems associated with sexual maturation such as lower growth rates, increased incidence of diseases and deterioration of the organoleptic properties. Triploidy can also be used to increase the viability of some hybrids, and is regarded as a potential method for the genetic containment of farmed shellfish and fish. This review focuses on some current issues related to the application of induced polyploidy in aquaculture, namely: 1) the artificial induction of polyploidy and the effectiveness of current triploidisation techniques, including the applicability of tetraploidy to generate auto- and allotriploids; 2) the performance capacity of triploids with respect to diploids; 3) the degree and permanence of gonadal sterility in triploids; and 4) the prospects for the potential future generalised use of triploids to avoid the genetic impact of escapees of farmed fish and shellfish on wild populations. Finally, directions for future research on triploids and their implementation are discussed.
Aquaponics is the integration of aquaculture and hydroponics. There is expanding interest in aquaponics as a form of aquaculture that can be used to produce food closer to urban centers. Commercial aquaponics uses methods and equipment from both the hydroponics and aquaculture industries. There have been few studies of commercial-scale aquaponics production, and the purpose of this research was to document the production methods, crop and fish yields, and profitability of commercial aquaponics in the United States (US) and internationally. An online survey was used for data collection, and 257 respondents met the inclusion criteria for the study. Eighty-one percent of respondents lived in the US, and the remaining respondents were from 22 other countries. The median year that respondents had begun practicing aquaponics was 2010. A total of 538 full-time workers, 242 part-time workers, and 1720 unpaid workers or volunteers were employed at surveyed organizations. The most commonly raised aquatic animals by percent were tilapia (69%), ornamental fish (43%), catfish (25%), other aquatic animals (18%), perch (16%), bluegill (15%), trout (10%), and bass (7%). Production statistics, gross sales revenue, investments, and sales outlets for operations are reported and compared to other fields of aquaculture and agriculture. A multivariable logistic regression model was used to study which factors were associated with profitability (as a binary outcome) in the past 12 months. Several factors were significantly associated with profitability: aquaponics as the respondents' primary source of income (p < 0.01; Odds Ratio: 5.79; 95% Confidence Interval: 3.8–9.0), location in US Department of Agriculture plant hardiness zones 7–13 (p < 0.01; OR: 4.17; 95% CI: 3.2–5.5), gross sales revenue ≥$5000 (p < 0.01; OR: 3.58; 95% CI: 2.2–5.8), greater aquaponics knowledge (p < 0.01; OR: 2.37; 95% CI: 2.0–2.9), and sales of non-food products (e.g., supplies, materials, consulting services, workshops, and agrotourism) (p = 0.028; OR: 2.13; 95% CI: 1.1–4.2). Our survey findings provide a better understanding of the business of aquaponics, which may enhance future commercial operations.