An 8-week feeding trial was designed to investigate the effects of varying dietary lipid and lysine levels on the growth, feed utilization, and blood characteristics of juvenile grass carp (Ctenopharyngodon idella). Six diets were formulated to contain one of three lysine levels (1.5, 1.7, and 2.0%) and one of two lipid levels (2.4 and 5.4%). Each diet was randomly assigned to triplicate tanks of 30 juvenile fish (initial body weight, 3.00 ± 0.02 g). The results showed that the weight gain, specific growth rate, feed efficiency, protein efficiency ratio, nitrogen retention, and lipid retention were significantly affected by dietary lipid and lysine levels (P < 0.05). However, no significant difference was observed in survival among the treatments (P > 0.05). All growth and feed efficiency indices decreased with an increasing dietary lipid level and significantly improved with lysine supplementation (P < 0.05). The dietary lipid levels significantly influenced the moisture and lipid contents of the whole body and muscle: the lipid content of tissue significantly increased with increasing dietary lipid and was inversely correlated with tissue moisture content (P < 0.05). The hepatosomatic index, intraperitoneal fat index (IPF), and serum cholesterol and triacylglycerol contents were significantly higher in fish that were fed the high-lipid diet (P < 0.05). Fish fed the low-lipid diet showed significantly higher amino acid concentrations compared to those fed the high-lipid diet, and the amino acid content improved with lysine supplementation (P < 0.05). Furthermore, dietary lipid, lysine, and their interaction had significant effects on growth performance, IPF, and tissue lipid content (P < 0.05). The results of the present study suggest a positive effect of dietary lysine supplementation on the growth and feed efficiency, serum lipid metabolism improvement, and reduction of IPF in juvenile grass carp.
Chinese soft-shelled turtle (Pelodiscus sinensis) is a favorite food for the Asian because of its high nutritional and medicinal value. Based on an estimate production of 350,000 MT in 2015, soft-shelled turtle culture industry in China values US$5.22 billion. In central China, overwinter in greenhouse is necessary for the juvenile turtle. The use of coal boiler to heat up the water to 30 °C is a common practice, however, brings in air pollution and CO2 emission too. A modern greenhouse equipped with ground source heat pump was built in 2010 and operated during 2014–2015 for 10 months to culture juvenile turtle. Besides heating system, the other innovative features such as skirt-shaped 3-D shelter, underwater feeding platform wok-shaped tank bottom with central drainage, and semi-homemade soft shell-shaped pellet together achieved excellent rearing performance, such as high turtle productivity of 23.7 kg m−2, high survival 86%, low feed efficiency-feed conversion rate 1.26 and good water quality-dissolved oxygen >5 mg L−1, and nitrite and ammonia concentration all time within safe range. Moreover, it is a lucrative business which brought in an estimated net profit of 76%.
Accurate, rapid, and specific methods are required to identify pathogens for controlling bacterial diseases in fish. Various microbiological and biochemical methods are used to isolate and identify pathogens, but they are not adequately efficient and/or accurate. For example, distinguishing between Streptococcus iniae and Lactococcus garvieae is difficult via microbiological tests. Moreover, these bacteria often cause concurrent infections. Therefore, early and accurate identification of bacterial pathogens in trout is of utmost importance to prevent possible damage. Because of this, the multiplex polymerase chain reaction (multiplex PCR) method was optimized for simultaneous identification of bacterial infections caused by Yersinia ruckeri, S. iniae, and L. garvieae, three harmful bacteria of great importance in aquaculture. Multiplex PCR reaction was optimized on control samples, and the sensitivity and specificity of the test were evaluated. Multiplex PCR reaction was then performed on DNA isolated from samples collected from fish-breeding farms and transported to the laboratory. Multiplex PCR was found to be an accurate and sensitive method to identify simultaneously different species of bacteria.
The veined rapa whelk Rapana venosa (Valenciennes, 1846) is an important and valuable fishery resource but has not been cultured on a large scale. We studied the effects of environmental factors, temperature, salinity, diet, and stocking density, on growth and survival of larvae to determine optimal artificial culture conditions. The optimal temperature was 25–31 °C at 30 ppt at densities of about 200 veligers per liter, under which the mean shell length (737–1006 μm) and survival rate (36–45%) were higher than those held at other temperatures. When cultured under a salinity of 25 ppt at 25 °C with densities of about 200 veligers per liter, larvae had the highest mean shell length (878.45–917.88 μm) and survival rate (29.75%). Larvae were fed a mixed diet, Pseudoisochrysis paradoxa + Tetraselmis chui + Chlorella vulgaris. Optimal stocking density was 300 veligers per liter for the first 5 days and was 100 veligers per liter afterward at 25 °C and 30 ppt.
The brine shrimp Artemia remains among the most important food used in fish and crustacean larviculture, and the study of its cysts’ nutritional quality is of great importance for products selection. Fatty acids (FAs) from decapsulated cysts of two bisexual (A. salina) and three parthenogenetic strains (A. parthenogenetica) from Algeria have been analyzed by gas chromatography. The aim was, first, to check the suitability of these strains as food for aquaculture and, second, to evaluate the FAs’ efficiency in inhibition of some of the fish pathogen’s activities. Percentages of total lipids were between 7.78 and 24.55% for the parthenogenetic strains of Bethioua and Sidi Bouziane salterns, respectively. Twenty-three FAs have been detected, and a high value of eicosapentaenoic (EPA; 20:5n-3) was observed in the parthenogenetic strain of Sidi Bouziane with 16.25 ± 0.08% (39.89 mg g−1 dry weight). The highest value of α-linolenic (ALA; 18:3n-3) was observed in A. salina from Chott Marouane with 22.28 ± 0.16%, (30.72 mg g−1 dry weight). The results of the antimicrobial screening assay of FA extracts showed their inhibitory activity against six fish pathogens. In comparison with ampicillin (Amp) and kanamycin antibiotics, all the studied strains of Artemia, except Bethioua, had better antimicrobial effect of their FAs against Vibrio anguillarum (gram-negative) than Amp. Streptococcus agalactiae (gram-positive) was the most resistant against Artemia’s FAs. Decapsulated cysts with the highest proportions of PUFAs and rich in ALA and linoleic were the most effective against the bacterial growth. Regarding the FAs’ composition and their antibacterial properties, Algerian strains of Artemia are good candidates for use as food in larviculture.
Betanodavirus or nervous necrosis virus (NNV) is responsible for viral nervous necrosis (VNN) of fishes and is associated with mass mortalities of various fish species throughout the world. Here, we report for the first time Betanodavirus infection in Arabian Gulf region of the Kingdom of Bahrain. The present study is also the first report of mortality due to NNV infection in sobaity seabream Sparidentex hasta. NNV was detected in reared fry of gilthead seabream Sparus aurata and adults of sobaity seabream and brown-spotted grouper Epinephelus chlorostigma using nested PCR. In the present study, the rearing unit recorded 100% mortality in fry of gilthead seabream and 24 and 63% mortalities were recorded in different age groups of adult sobaity seabream due to VNN. Classical clinical signs of VNN such as body discoloration, loss of appetite and abnormal swimming behaviour were observed in fry of gilthead seabream. Histopathological studies revealed characteristic vacuolation and degeneration of brain and ocular tissues of sobaity seabream. However, brown-spotted grouper carried subclinical NNV infection, and there was no mortality in the group. Sequencing of nested PCR products and real-time PCR further confirmed the presence of the virus.
The paper provides a first look into the fatty acids (FA) of young Amphioctopus fangsiao. Laboratory-hatched, 1-day-old juveniles (NH) were analyzed to identify the basal FA profile. To determine dietary effects on FA, individually kept juveniles (FD) were fed mysids once daily. Others were subjected to starvation (ST) to examine which FA may be used and which would be conserved. Treatments run for 25 days post-hatch, at which time ST and FD were analyzed to record FA changes. The dominant FA were 16:0, eicosapentaenoic (EPA), and docosahexaenoic (DHA), overall accounting for 40–60%. Monounsaturated FA (MUFA) were the highest in FD at 24.2% whereas highly unsaturated FA (HUFA) were most prominent in ST at 45.5%, followed by NH at 40.2%. Among n-3 HUFA, DHA was dominant in ST at 22.9 mg g−1 dry weight (DW), the role assumed by EPA in FD at 11.5 mg g−1 DW. Consequently, the DHA/EPA ratio was the lowest in FD. Arachidonic was the most abundant n-6 HUFA, representing >5% in total FA. However, n-6 FA were not prevalent, resulting in high n-3/n-6 in all juveniles. It could be argued that young A. fangsiao require n-3 HUFA, particularly DHA and EPA at a ratio of ideally >1.5 and to a lesser extent n-6 HUFA. Juveniles fed on a low lipid, high n-3 diet increased their MUFA content while maintaining high HUFA. Despite changes in the FA of ST individuals, it appears food-deprived A. fangsiao do not depend on FA mobilization for energy production.
Based on the data of China’s ten coastal regions from 2003 to 2012, this paper conducts a data envelopment analysis (DEA) model to evaluate China’s mariculture efficiency with undesirable outputs using Seiford’s linear converting method. The result shows the average efficiency is about 0.714, relatively low and without ascending over time. The efficiency of different provinces differing obviously, ones of Tianjin and Guangxi are high while Hebei and Jiangsu’s are low. Efficiency-influencing factors are analyzed with the Tobit model, revealing that technology extension convenience and technology level have positive influence, while training intensity factor has negative one. The species structure factor and regional factor have also been found to have significant impact on the efficiency.
Knowledge of the pedigree relationships between individuals is a prerequisite in genetics research, and the application of molecular markers for pedigree analysis has been a booming science for over a decade. Owing to the high variability, microsatellites are considered as the marker of choice for studies on pedigree analysis. Nevertheless, single nucleotide polymorphisms (SNPs) have been increasingly used for this purpose in recent years due to the low mutation rate and genotyping error rate. To compare the utility of microsatellites and SNPs in assigning parentage in the Pacific oyster (Crassostrea gigas), we genotyped 384 parental and offspring individuals using 12 multiplexed microsatellites and 50 SNPs. In this study, all microsatellite loci showed high informative (PIC >0.5), while most SNPs were middle informative (0.25 <PIC <0.5). CERVUS simulations revealed that using nine microsatellites or 38 SNPs, the power of parental assignment could reach 100%. Pedigree analysis of real offspring demonstrated that 100% of the offspring were unambiguously assigned to a pair of parents when nine microsatellites or 50 SNPs were used. For microsatellites, the combined exclusion power with one parent known (EXCL2) could reach one when three microsatellites multiplex PCRs or more were used, whereas EXCL2 was 0.9999 for the 50 SNPs. In general, six SNPs were needed to obtain an equivalent exclusion power for pedigree analysis with a microsatellite locus in C. gigas. The information obtained in this study will be useful for assigning parentage in C. gigas using both marker systems.
A 45-day feeding trial was conducted to study the effect of replacing dietary fish meal (FM) with corn gluten meal (CGM) on diet digestibility and growth and proximate body composition of Asian seabass (Lates calcarifer) fingerlings (21.1 ± 0.95 g). Five isonitrogenous and isocaloric diets, formulated to contain 40% protein and 10% lipid, were prepared with fish meal replacement at 0 (control), 5, 10, 15, and 20% (w/w basis) using CGM. The trial was carried out in 1000-L fiber-reinforced polymer (FRP) tanks with three replicates (each containing 20 fish) for each treatment, and fish were hand fed in excess twice daily at 10.00 and 16.00 h. There was no significant difference in final body weight, average daily gain, and survival for fish fed the CGM0, CGM5, and CGM10 diets, with fish in these treatments performing better than the others. Feed conversion ratios for fish fed CGM0 (1.73 ± 0.05 g feed /g gain), CGM5 (1.65 ± 0.06 g feed g−1 gain), and CGM10 (1.84 ± 0.07 g feed g−1 gain) were better than for the other treatments. Protein retention (28.85 ± 0.65%) and energy retention (20.60 ± 0.39%) were better in the group fed with CGM5 than the other treatments. Apparent digestibility coefficients of dry matter (65.1 ± 0.3, 64.7 ± 0.2%), protein (91.6 ± 0.5, 91.7 ± 0.3%), and energy (79.0 ± 0.27, 8.4 ± 0.1%) were highest for the CGM5 and CGM10 diets. Highest crude lipid (7.29 ± 0.09%) and gross energy (7.19 ± 0.05 kJ g−1) were observed in fish fed the CGM 20 diet. The results indicate that CGM is a potential feed ingredient for seabass and can be included at 10% of the diet without compromising digestibility and growth.
In this study, Spirulina platensis (Cyanophyceae) was cultured at five mediums with different amounts of sodium nitrate and three different temperatures. The study was conducted at 1600 lx light intensity and a pH value of 9. The influences of nitrate amounts and temperature on biomass growth and lipid amount were studied during 20 days. The best biomass growth (1.039 ± 0.668 g L−1 dry weight and 0.780 ± 0.501 optical density) for S. platensis was obtained from the group with the temperature value of 35 °C and 2.5 g L−1 of sodium nitrate. The highest lipid production (4.70 ± 0.067% dry weight) was in the nitrate-free medium at 15 °C. The best results for biomass growth and lipid production were obtained from the group at 35 °C and 1.25 g L−1 of sodium nitrate (P < 0.05). At the end of the study, it was determined that algal biomass increased with increasing the nitrate amount but the produced lipid by the algae decreased. Intensive production was performed in accordance with the culture conditions of the most productive groups and biodiesel was obtained from the algae. The density, viscosity, and flash point of the biodiesel were calculated as 0.78, 4.67, and 107 °C, respectively.
Tilapia is an internationally farmed trade species recommended by the United Nations Food and Agriculture Organization, which is promoted and farmed in more than 100 countries and regions. In China, tilapia culture is a promising aquaculture business and it occupies an important position in global tilapia culture. In this study, profitability analysis was used to analyze the production costs and economic benefits of different farming sizes among the main tilapia-producing areas of China. Sensitivity analysis was conducted to analyze the impact of uncertainty factors on net profit of tilapia farming. Details of the costs and benefits of tilapia culture in China could support financial planning by fish farmers. The economic profit indices measured in this study comprised the total profit, gross income, profit margin, and benefit-cost ratios. The results indicated that large farms has the highest cost and the highest cost-profit margin among the three categories, and the small farms has the lowest cost and profit margin, while the cost and profit margin of medium size are between the large and small sizes. Sensitivity analysis shows that the net profit of tilapia is very flexible to the change of price, feed, rent, and fixed cost, of which price elasticity was the highest, followed by the feed, rent, and fixed cost. According to the problems existing in the tilapia farming, some policy suggestions were put forward for sustainable tilapia culture.
Super-intensive, biosecure, recirculating shrimp production systems (SIBRSPS) have been developed to prevent disease outbreaks and improve profitability. To evaluate the economic viability for SIBRSPS, the Hanson-Posadas bioeconomic model was developed to conduct analysis of net present values (NPVs), internal rate of returns (IRRs), and payback periods. The objective of this study is to develop a profit maximization model, as an enhancement to the Hanson-Posadas bioeconomic model, to determine the optimal harvesting week, size, and batch number per year and evaluate the economic viability for the SIBRSPS. Biological growth and feed functions in the profit maximization model were estimated using data from experiments conducted at the Gulf Coast Research Laboratory (GCRL), Waddell Mariculture Center (WMC), and the Oceanic Institute (OI) during 2003 through 2006. Results found that Pacific white shrimp (Litopenaeus vannamei) growth and feed significantly (P < 0.01) responded to number of weeks farmed as quadratic concave function shapes in GCRL and WMC and as linear in OI. The optimal harvest week, size, and batch number per year are 12th–18th week, 18–21 g, and approximately three to four batches, respectively, depending on the location. The economic viability of SIBRSPS is questionable, with positive NPVs ($9.35, $2.27, and $0.36 million) experienced only in three (OI-14, WMC-9, and WMC-8, respectively) out of seven experiment scenarios. Profitability is dependent on economic factors including L. vannamei prices and establishment and maintenance costs of SIBRSPS as well as biological factors such as stocking density, initial puerulus (PL) size, growth rates, feed conversion rates, and survival rates.
Crustacean aquaculture production has developed rapidly in recent years because there has been an increase in crustacean market demands in different regions of the world. The growth rate of the most cultured crustacean species depends on genders. Therefore, monosex crustacean aquaculture, all male or all female, is more suitable for achieving higher yields, with the ecological benefits of reducing the risk of cannibalism. In addition, feminization is also appropriate for increasing individual number in populations because males are able to copulate with more females. For this reason, sexual manipulations are important in crustacean reproduction units. This review focuses on the sex differentiation mechanism and the use of different strategies for feminization of economically important crustaceans. In this review, feminization strategies are divided into two main methods: direct feminization and indirect feminization (masculinization). Direct feminization includes (1) ablation of androgenic gland (AG), (2) silencing and suppression AG and androgenic gland hormones (AGHs), (3) hormone therapy (i.e., 17β-estradiol), and (4) polyploidy induction. This review also emphasizes how feminization is carried out for crustaceans belonging to the different sex determination systems (ZW or XY) by using indirect method. The intension of controlling sexual differentiation for crustaceans will continue to increase in the next a few years, either for basic research or for its utilization to crustacean aquaculture; hence, this review will be profitable for crustacean farmers and researches.
The present study was conducted to investigate the impact of adding commercial feed additives Agrimos® (combined yeast, Saccharomyces cerevisiae mannan oligosaccharides, and β-glucan) in the diet of Macrobrachium rosenbergii during the juvenile stage on growth performance, feed utilization, and immunological parameters. Four hundred and fifty juveniles of average weight 2.2 ± 0.02 g were divided into five experimental groups with three replicates each. The experiment was conducted for 56 days. Five isocaloric and isonitrogenous diets were formulated to be contain 350 g kg−1 crude protein and 19.4 MJ GE; four diets contain different levels of Agrimos® (1.5, 2, 2.5, and 3 g kg−1) in addition to control diet without Agrimos®. Final body weight, weight gain, and specific growth rate of Agrimos® fed groups were significantly higher (p < 0.05) than the control group. Survival rate of the Agrimos® fed groups and control was not significantly different (p > 0.05). In addition, the feed conversion ratio and protein efficiency ratio in treatments supplemented by Agrimos® were significantly better (p < 0.05) than those fed the control diet. Concerning the influence of the Agrimos® on proximate composition of carcass, no significant differences (p > 0.05) were observed among different treatments. Increased immune response was observed in experimental groups with the 2.5 g kg−1 Agrimos® concentration yielding the significantly higher (p < 0.05) total hemocyte count and phenoloxidase. In conclusion, the additions of Agrimos® in the diet 3 at a concentration of 2.5 g kg−1 improved and enhanced the growth performance and feed utilization of M. rosenbergii juveniles.
In recirculating aquaculture, a bacterial biofilter is applied to convert ammonium, excreted by the fish, to the non-toxic nitrate. Unfortunately, nitrifying bacteria produce off-flavor compounds that lower fish quality. We investigated, by calculations and estimations, possibilities to replace the biofilter by autotrophic organisms that incorporate ammonium in biomass, consume other mineral nutrients and produce marketable biomass and oxygen. The capacity of microalgae, macroalgae, duckweed, strawberry, and tomato to assimilate ammonium was calculated, using data from an existing Finnish fresh water fish farm. Microalgae were found to be the most effective for ammonium removal, and they would be able to consume the ammonium produced by a fish farm if the algae were grown in a facility with approximately twice the area of the fish farm itself. Macroalgae and duckweed appeared to be the second best option for ammonium removal, and strawberry and tomato were predicted to have a somewhat smaller capacity for ammonium removal. Due to low ammonium content, microalgae cannot be cultivated in the recirculating water, but rather the nutrients should be allowed to diffuse through a semipermeable membrane to microalgae.
A 90-day experiment consisting of two groups, a biofloc treatment and a control treatment, was performed in six indoor cement ponds to investigate the effectiveness of biofloc technology (BFT) for maintaining water quality and growth performance of Macrobrachium rosenbergii in a zero-exchange water system. Molasses was added to the biofloc ponds with the C/N ratio of 20:1 based on the amount of daily feed. The floc volume in the biofloc group increased gradually (28.72 mL L−1) along with molasses addition, but the value in the relative control group remained at low levels (0.40–4.97 mL L−1) (P < 0.05). A total of 4.97% Bacillus, 4.20% Lactococcus, and 9.65% Nitrospira were determined in the biofloc water, and these values were significantly higher than that in the control water (P < 0.05). Ammonia-N, nitrite-N, nitrate-N, and total nitrogen concentrations in the biofloc water were significantly lower than that in the relative control group (P < 0.05). Potassium orthophosphate (PO4 −-P) and total phosphorous (TP) concentrations increased consistently in both groups. The same-day value of PO4 −-P concentration in the control group (6.37–12.96 mg L−1) was 1.5 higher than that of the biofloc group (4.66–7.99 mg L−1) from day 60 to day 90 (P < 0.05). Significant differences in TP concentration (P < 0.05) were noted between the control and biofloc groups from the 15th day to the 30th day and from the 60th day to the 90th day. The biofloc treatment resulted in a 10.62% higher survival rate, a 27.55% higher weight gain rate, and a 7.13% higher specific growth rate (P < 0.05). The findings of the present study demonstrated that BFT effectively promoted water quality, as well as growth and survival of M. rosenbergii, by regulating the inorganic nitrogen and phosphorus dynamics.
Probiotic effect of a consortium of putative lactic acid bacteria on Labeo rohita was investigated with emphasis on growth performance, immune response, and disease resistance against Aeromonas hydrophila. Fish were fed either a lactic acid bacteria-supplemented diet or a control diet for a period of 30 days. At the end of the experiment, probiotic fed group showed a significant improvement in weight gain percentage, specific growth rate, and feed conversion ratio along with increased respiratory burst activity of blood phagocytes and serum antiprotease activity level. Quantitative real-time PCR showed significant upregulation of IL-10 gene in kidney, intestine, and liver of probiotic-treated group, whereas TNF-α gene was significantly upregulated only in liver and intestine. HSP70 gene was significantly upregulated in intestine but downregulated in liver on day 15. Challenge with Aeromonas hydrophila on day 30 of probiotic feeding showed a significant increase in survival percentage of treated (93.33 %) over the control group (33.33 %). Further challenge after 20 and 40 days of withdrawal of probiotic showed higher survival percentage (60 and 40 %, respectively) in withdrawn group compared to control although difference was statistically insignificant. The consortium of putative probionts may serve simultaneously as an immunomodulating feed additive useful for disease protection and growth enhancer in eco-friendly freshwater aquaculture practices. However, feeding at regular interval with probiotic supplemented diet is suggested for a prolonged immunity.
The use of cultivated seaweeds as a feedstock for multiple industrial applications has gained increasing interest in the Western World over the past decades. Norway has an extensive coastline and a well-established aquaculture sector offering suitable preconditions for developing large-scale cultivation of seaweed biomass both in monoculture and in Integrated Multi-Trophic Aquaculture (IMTA) systems. Recent efforts from research, industry and public authorities have been committed to develop a Norwegian bio-economy based on cultivated seaweed, focusing on cultivation and processing of the biomass. This review reports on the status of seaweed aquaculture in Norway, supported by production data collected since the delivery of the first commercial cultivation permits at sea in 2014. Although novel product developments are currently limited, future industrial perspectives based on cultivated biomass are being discussed. Upscaling from experimental cultivation schemes to commercial production requires a thorough assessment of the risks and benefits associated with seaweed aquaculture, as well as the development of a regulative framework adapted to this industry. Issues associated with upscaling the macroalgal production that needs to be addressed includes (i) genetic interactions between cultivated and wild crops, (ii) impacts of seaweed cultivation on surrounding ecosystems, (iii) epiphytes and diseases, (iv) area utilization and (v) threats from climate change. Addressing these issues and adapting production practices will ensure the environmental and economic sustainability of an emerging industry based on cultivated seaweed biomass in Norway.
The present experiment was carried out in order to evaluate the potential adjuvant effect of bovine lactoferrin (bLF) in modulating the specific antibody (Ab) response to an exogenous protein, the human-γ-globulins (HγG), injected intraperitoneally in rainbow trout Oncorhynchus mykiss (Walbaum 1792). Moreover, serum natural antibody (NatAb) level, serum total immunoglobulin (IgM) level and specific Ab response to bLF were also analysed. Experimental data showed that HγG is able to stimulate a specific Ab response when not adjuvanted with Freund’s complete adjuvant (FCA), whereas bLF induces a specific Ab response only if adjuvanted with FCA. Statistical analyses revealed that neither bLF or FCA administered singly had significant effects on serum NatAb and IgM levels, whereas the specific immune response observed against HγG when adjuvanted with bLF was comparable to that achieved when FCA was used as the adjuvant. These results provide evidence of the potential for bLF to be used as an adjuvant for salmonids.