Showing papers in "Aquaculture International in 2017"

Seaweed aquaculture in Norway: recent industrial developments and future perspectives

Abstract: 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.

Biofloc technology: an emerging avenue in aquatic animal healthcare and nutrition

Abstract: Biofloc is a conglomeric aggregation of microbial communities such as phytoplankton, bacteria, and living and dead particulate organic matter. Biofloc technology involves manipulation of C/N ratio to convert toxic nitrogenous wastes into the useful microbial protein and helps in improving water quality under a zero water exchange system. It may act as a complete source of nutrition for aquatic organisms, along with some bioactive compounds that will enhance growth, survival, and defense mechanisms, and acts as a novel approach for health management in aquaculture by stimulating innate immune system of animals. Nutritionally, the floc biomass provides a complete source of nutrition as well as various bioactive compounds that are useful for improving the overall welfare indicators of aquatic organisms. Beneficial microbial bacterial floc and its derivative compounds such as organic acids, polyhydroxy acetate and polyhydroxy butyrate, could resist the growth of other pathogens, thus serves as a natural probiotic and immunostimulant. The technology is useful in maintaining optimum water quality parameters under a zero water exchange system, thus prevents eutrophication and effluent discharge into the surrounding environment. Moreover, the technology will be useful to ensure biosecurity, as there is no water exchange except sludge removal. The technology is economically viable, environmentally sustainable, and socially acceptable.

The use of different aerators on Litopenaeus vannamei biofloc culture system: effects on water quality, shrimp growth and biofloc composition

Abstract: This study evaluated the effects of different aeration types on water quality, shrimp growth and biofloc composition in a Litopenaeus vannamei culture. The study was conducted with three treatments: (1) PR—propeller aspirator pump aerator; (2) VP—vertical pump aerator; and (3) BL—diffused air blower. The study was performed in a greenhouse with nine 35,000-L rectangular tanks. Water quality parameters (temperature, salinity, dissolved oxygen, pH, ammonia, nitrite, nitrate, settleable and suspended solids) were measured along the 33 experimental days. Moreover, samples were collected to quantify the microorganisms present in the tanks. At the end of the study, samples of the biofloc of each tank were collected to proximal analysis. Throughout the experiment, the temperature, pH, salinity and alkalinity were maintained within the recommended levels for L. vannamei. The propeller treatment showed a concentration of total ammonia above the recommended levels and lower densities of ciliates and flagellates, most likely because of inadequate biofloc formation in this treatment. The final weight was higher in the blower and propeller treatments. However, survival was lower in the propeller treatment compared to the other treatments. The results of this study suggest that diffused air systems (air blower) improve the formation of biofloc and growth performance of L. vannamei.

Economic profitability of tilapia farming in China

Abstract: 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.

Effects of different combinations of Bacillus on immunity and antioxidant activities in common carp

Abstract: Bacillus can not only improve the ecological environment of aquaculture water, but also improve the immunity of aquaculture animals, inhibit the reproduction of pathogenic microorganisms and reduce the incidence of disease. The present study represented the effect of different combinations of Bacillus on immunity and antioxidant activities in common carp. A total of 240 fish were randomly divided into four groups: control group (basal diet), experimental group I (add B. subtilis), experimental group II (add B. subtilis and B. licheniformis), and experimental group III (B. subtilis, B. licheniformis, and B. cereus). Compared with the control group, the carp in experimental group II displayed a significantly elevated phagocytic percentage (up to a 20.2% increase; P 0.05). Our results indicated that dietary Bacillus enhanced the performance of the common carp immune response and that a mixture of strains elevated the antioxidant ability.

Probiotic effect of Streptomyces strains alone or in combination with Bacillus and Lactobacillus in juveniles of the white shrimp Litopenaeus vannamei

Abstract: We studied the effect of two Streptomyces strains, alone and combined with Bacillus and Lactobacillus, on the growth, microflora, hemocyte count, and superoxide dismutase (SOD) activity of the shrimp Litopenaeus vannamei. Eight experimental groups were fed for 30 days either with N7 (Streptomyces N7), RL8 (Streptomyces RL8), Strep (Streptomyces N7 and RL8), Lac (Lactobacillus graminis), Bac (a Bacillus mixture), or a combination of Lac-Strep, Bac-Strep, and Mix (a mixture of Bac, Lac, and Strep). A non-probiotic fed group served as the control. After treatment, shrimps were challenged with Vibrio parahaemolyticus and survival was recorded for 4 days. The Bac-Strep group showed significantly better (P < 0.05) growth performance than the control group, followed by good but not significant performance of groups N7, RL8, and Strep. All Streptomyces-containing groups, except Mix, showed a significant reduction of Vibrio from hepatopancreas, the same as Bac-Strep from water, whereas they produced a mild reduction of heterotrophs. All probiotic-fed groups had a higher hemocyte count than the control, but it was only significant for Strep and Bac-Strep. Challenging shrimps with V. parahaemolyticus stimulated the SOD activity of probiotic-fed groups, except for RL8, with higher but not significant SOD, and the groups N7 and Strep. All probiotic-fed groups showed a significantly higher survival rate than the control group, except for N7 and Strep. This study revealed that some Streptomyces strains alone or combined with other genera, primarily Bacillus, exert a probiotic effect on shrimps by improving growth parameters, regulating immune response, modulating host and water microbiota, and increasing resistance to disease.

Changes of shrimp farming in southwest coastal Bangladesh

Abstract: Shrimp (Penaeus monodon) farming is a traditional aquaculture in southwest coastal Bangladesh Changes in both the farming practice and yield of shrimp since the advent of commercial production in this area are evident in scientific studies We assessed the historical perspective of shrimp farming indicating the major phase changes and present situation of the shrimp farming practice including recent changes in yield and cost-benefit A systematic random sampling method was employed to conduct a total of 240 questionnaire surveys, 24 focused group discussions, and 60 key informant interviews in six sub-districts (upazila) from southwest coastal Bangladesh We identified four major phase changes in the history of shrimp farming in southwest coastal Bangladesh and found that shrimp mixed culture is the most preferable form of extensive cultivation at present Shrimp farmers’ perceptions about changes in shrimp yield and changes in availability of ecosystem services represent declining trends over the last two decades For 2015, shrimp yield was not significantly different with respect to salinity levels The net benefit from shrimp mixed culture in 2015 was 121,000 taka/ha, which is 235 times higher compared to the net benefit from only shrimp (51,500 taka/ha) In this context, promoting shrimp mixed cultivation could be a management solution for sustainable development of shrimp farming in southwest coastal Bangladesh The National Shrimp Policy of the government also emphasized on promoting environment-friendly shrimp mixed cultivation for sustainable development of shrimp farming However, more institutional support such as training, extension support, technical assistance, and credit facility is required to implement the policy

Photo-thermal manipulation for the reproductive management of pikeperch Sander lucioperca

Abstract: The aim of the present study was to investigate the effect of photoperiod regime combined with thermal treatment (PTT) on maturation of three-year-old pikeperch (Sander lucioperca). To induce the onset of maturation, all treatment groups underwent a wintering phase of 3 months at 12 °C and 12-h light-to-12-h dark. Controls were maintained at 23 °C and 12-h light-to-12-h dark throughout the trial. After the wintering phase, the PTT groups experienced regimes with 8-, 10-, 12-, and 14-h light for 4 months at 14 °C referred to as photo-thermal treatment (PTT). The four PTT groups as well as the control were studied in triplicates, with 12 fish per tank. We assessed gonad development and maturation by histological analysis, sex steroid plasma concentrations (17β-estradiol, testosterone, and 11-ketotestosterone) and, at the end of the experiment, mRNA expression of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in the pituitary. As expected, both male and female pikeperch initiated reproductive maturation during the wintering phase, which was confirmed through histological analysis and sex steroid measurements. During wintering, the onset of maturation in females was confirmed by the increasing diameter of ovarian follicles (217 ± 65 to 800 ± 97 µm), the developmental stages (50 % mid and 21 % late vitellogenic females), concomitant with elevated 17β-estradiol (E2) plasma concentrations reaching 2600 ± 1500 pg/mL, compared to 380 ± 230 pg/mL at the onset of the experiment. Similarly in males, maturation was indicated by peak concentrations of the androgens observed within the first 2 months of wintering (testosterone 21 ± 12 ng/mL first month, 11-ketotestosterone 5.7 ± 3 ng/mL second month). Subsequently, the photoperiod treatments after the wintering phase influenced the progression of reproductive maturation. During the PTT, follicle diameter increased irrespective of the light regime from 800 to more than 1100 µm, but the progression of the vitellogenesis was differentially modulated by the photoperiod. Already after 1 month of the PTT, 92 and 86 % of females reared at 12- and 14-h light per day were in a late vitellogenic stage. After 2 months, females with mainly atretic follicles were observed under long light conditions (14 h of light), indicating overripeness and spawning. In contrast, 82 and 72 % of the females reared at 8- and 10-h light per day were still in the final stage of vitellogenesis at the end of the experiment and thus ready to undergo final maturation. Concomitant to the histological outcomes, highest E2 concentrations were observed under long-day conditions (12, 14 h) in females with peaks of 4200 ± 3300 (12 h of light) and 6800 ± 4200 pg/mL (14 h of light). In male pikeperch, ongoing spermatogenesis was indicated by rising androgen levels especially under long-day conditions (14 h of light) reaching peak levels of 27 ± 21 ng/mL testosterone and 39 ± 91 ng/mL of 11-ketotestosterone at the end of the experiment. In all PTT, the mRNA expression of FSH and LH was significantly elevated compared to the control, confirming the activation of the hypothalamus–pituitary–gonad axis. Here, no effect between the different light regimes was detected, neither in males nor females. Thus, photoperiod revealed a slight influence on male and female pikeperch maturation when combined with an effective thermal treatment and therefore can be explored as a cheap and easy-to-handle fine-tuning tool for artificial pikeperch reproduction.

Substitute of soy protein concentrate for fish meal in diets of white shrimp (Litopenaeus vannamei Boone).

Abstract: The present study was conducted to evaluate the effects of partially replacing dietary fish meal (FM) with soy protein concentrate (SPC) on growth, body composition, digestive enzyme activities, and nutrient digestibility of white shrimp. Five isonitrogenous diets with SPC inclusion levels of 0.0, 2.5, 5.0, 7.5 and 10.0%, were prepared to replace 0.0, 12.5, 25.0, 37.5, and 50.0% FM in basal diet containing 20.0% FM, respectively, and fed to white shrimp with an initial body weight of 1.80 g. After 49 days feeding, 5.0% SPC diet did not affect the growth of white shrimp (P > 0.05), but weight gain was decreased (P 0.05) among treatments except glycine (Gly). The above results indicated that 25% FM could be substituted by SPC, and the SPC inclusion level was 5% without negative effects on the growth of white shrimp.

An overview of motile Aeromonas septicaemia management

Abstract: Motile Aeromonas septicaemia is most commonly caused by Aeromonas hydrophila. It is an opportunistic pathogen causing disease in fish under stress. The bacterium produces a number of pathogenic factors, and the most important among them are the haemolysin and the aerolysin, provoking the disease. Freshwater and saltwater fish species are susceptible. The disease is manifested clinically with haemorrhages, ulcerations, abscesses, ascitic fluid and anaemia. Mortality rates are high, and they incur substantial economic losses, thereby necessitating timely measures of control for prevention and treatment. Therefore, the aim of this overview was to provide up-to-date information related to the control of motile Aeromonas septicaemia in fish through application of chemotherapeutic drugs, phytobiotics, probiotics, yeast extracts, vaccines and disinfectants.

Global status of production and commercialization of soft-shell crabs

Abstract: Commercial exploration of swimming crab is rapidly increasing worldwide. In 2015, total production of crabs (fisheries plus aquaculture) reached almost 1300 thousand tons. One of the most valuable marketing forms is called “soft-shell crab”. The internet is one of the most important marketing channels for soft-shell crab, with prices starting at US$3.5 a unit, but going up to US$8.00–10.00, depending on the size and presentation form of the product (live, cooled, frozen, or processed). In luxury restaurants, a dish containing one large animal may cost well over US$75.00. Increasingly, this market requires exporting companies to present some kind of quality certification of the product or process (mainly certifications related to food safety). Almost all soft-shell crab production is based on crabs caught in the wild, by either trawling or trapping. Crab populations are suffering from environmental impacts associated with human activity, so much that obtaining the raw material (crabs in pre-molt stage) has become the biggest challenge for companies that market soft-shell swimming crab nowadays. Even recognizing the aquaculture as an alternate form to acquire crabs, it is necessary to understand that technology for commercial crab cultivation is still incipient and restricted to some species of few genera, such as Scylla, Portunus, and Callinectes. The present article reviews and discusses the problems and challenges related to the productive chain of soft-shell swimming crab, and presents an overview of the worldwide market, identifying the main exporting and importing centers, and their respective trading methods.

Effects of Astragalus polysaccharides on antioxidant abilities and non-specific immune responses of Chinese mitten crab, Eriocheir sinensis

Abstract: This study assessed the effects of Astragalus polysaccharides (APS) on antioxidant abilities, non-specific immune responses, and immune protective efficacy (attacked by Aeromonas hydrophila) of Eriocheir sinensis, the most important Chinese freshwater crabs. A total of 720 crabs (initial mean weight 10.27 ± 1.58 g) were fed 60 days with six kinds of experimental diets containing graded dosages of APS (0, 300, 600, 900, 1200, 1500 mg/kg diets) in 18 outdoor cement tanks. The results showed that superoxide dismutase (SOD), catalase (CAT), total antioxidant capacity (T-AOC), lysozyme (LZM), and phenoloxidase (PO) activities of serum significantly increased (P 0.05); SOD, CAT, T-AOC, LZM, AKP, and ACP activities of hepatopancreas significantly increased (P < 0.05) with increasing APS dosages (0–1200 mg/kg diets); the increased maximal multiples of LZM and PO activities were higher than SOD, CAT, and T-AOC which increased. The results of A. hydrophila attack test showed that mortality rates significantly decreased (P < 0.05) with increasing APS dosages (0–600 mg/kg diets), and the highest immune protective rate was 49.4%. In short, APS could help E. sinensis to improve immune responses and may reduce the risk of disease attacks as one kind of effective immunopotentiator in diets, and the best additive dosage was 1200 mg/kg.

Growth performance, immune-physiological variables and disease resistance of common carp (Cyprinus carpio) orally subjected to different concentrations of Lactobacillus plantarum

Abstract: Nowadays, probiotics are among the most attractive food supplements for promoting animal’s growth and health condition with the aim of increasing production and lowering losses. Four hundred and eighty fish weighing 31.8 ± 2.6 g were randomly divided into four groups each in triplicates. Groups 1 to 3 were fed with commercial carp feed containing 0.7, 0.5, and 0.3 g (1.2 × 106, 0.9 × 106, and 0.56 × 106 cfu/g feed) probiotic Lactobacillus plantarum per kilogram feed for 80 days at 26 ± 1 °C, respectively. Group 4 received normal feed and was considered as control 1. Growth factors and some immunophysiological parameters were assessed on days 0, 20, 40, 60, and 80 of the trail. An overall increase in growth factors of probiotic-treated groups was seen, and final weight and condition factor of groups 1 and 2 were higher than control group (p ≤ 0.05). The highest specific growth rate and best feed conversion ratio were obtained in group 1. Red blood cell (RBC) count, hematocrit, and hemoglobin in probiotic groups were higher than control 1, but differences were significant for group 1 (p ≤ 0.05). White blood cell (WBC) count significantly increased in groups 1 and 2 compared to other groups (p < 0.05). Respiratory burst activity significantly increased in all probiotic fed groups with the highest level recorded in group 1 (p ≤ 0.05). Complement and lysozyme activities were significantly higher in group 1 followed by group 2 than both group 3 and control 1 (p ≤ 0.05). Also, serum bactericidal activity was significantly higher in group 1 than other groups (p ≤ 0.05). Serum total protein and immunoglobulin were higher in probiotic groups than control 1. No significant changes were seen in serum level of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH) among all groups. After challenging fish with virulent strain of Aeromonas hydrophila, the lowest mortality was obtained in groups 1 and 2, respectively (p ≤ 0.05). These data clearly show that application of probiotic L. plantarum in carp feed can not only improve the growth variables and immunophysiological responses of fish but also increase the fish disease resistance to motile Aeromonas septicemia caused by Aeromonas hydrophila. However, these positive improvements are dose dependent.

Growth phase significantly decreases the DHA-to-EPA ratio in marine microalgae

Abstract: Microalgae are the principal producers of long-chain polyunsaturated fatty acids (LC-PUFAs) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in marine ecosystems. Algae are used in aquaculture systems as direct or indirect feed for zooplankton, filter-feeding mollusks and larval stages of crustaceans and fish. Therefore, it is necessary to select nutrient-rich strains, with high levels of EPA and/or DHA, preferably during the stage of rapid growth. During the course of algal growth (exponential to stationary phase), many microalgal species accumulate lipids, especially triacylglycerols. However, relatively little is known about the effect of growth phase on LC-PUFA accumulation. In the present study, absolute and relative EPA and DHA levels of seven representative species of marine microalgae were determined during different growth phases in batch culture. Four species (Phaeodactylum tricornutum, Thalassiosira weissflogii, Thalassiosira pseudonana and Rhodomonas salina) accumulated fatty acids during growth. In all these species, intracellular EPA levels were higher during the late stationary growth phase than during exponential growth. In contrast, an increase in DHA content was not observed and therefore the DHA-to-EPA ratio was significantly lower in late stationary phase cultures. These results can be used to improve the nutritional value of microalgae cultivated for application in marine aquaculture systems.

Nitrogen budget in integrated aquaculture systems with Nile tilapia and Amazon River prawn

Abstract: The present work aims to describe the nitrogen (N) budget in integrated aquaculture systems with Nile tilapia (Oreochromis niloticus) and Amazon River prawn (Macrobrachium amazonicum) in earthen ponds, with and without the addition of different substrates. The experimental design was completely randomized, with three treatments (without a substrate, with a geotextile fabric substrate, and with a bamboo substrate) and four replications. Diet was the major input of N in the systems, ranging from ~65 to 71% and followed by inlet water (~26–31%). The portion retained in reared animals and periphyton ranged from ~21 to 25% (being ~21–24% in fish and prawns). The outputs that contributed most to the accumulation and release of N were, respectively, sediment (~24–38%) and N2 (~30–36%) emitted to the atmosphere. The addition of substrates did not improve the accumulation of nitrogen in the biomass of the target species. This suggests that the periphyton had a minor role on feed availability. In general, the systems were not efficient in using nitrogen since only ~22% of all available nitrogen was retained into prawn and tilapia biomass. On the other hand, the emission of N2 (an inert gas) to the atmosphere almost compensated the nitrogen supplied in the diet that was not assimilated by the reared animals and periphyton. In addition, data suggest that the integrated aquaculture in stagnant ponds may sequester substantial amounts of nitrogen from nutrient-rich aquatic environments and could be used as a mitigation tool.

Effects of dietary Biogen and sodium butyrate on hematological parameters, immune response, and histological characteristics of Nile tilapia (Oreochromis niloticus) fingerlings

Abstract: The present study was carried out to evaluate the use of Biogen and sodium butyrate (SB) as feed additives in the diet of Nile tilapia (Oreochromis niloticus) fingerlings, in two parallel experiments. Biogen was incorporated in isonitrogenous (35% crude protein) and isocaloric (19 MJ kg−1) diets at four levels (0.0 (control), 0.5, 1.0, and 2.0%), while SB was included at five levels (0.0 (control), 0.5, 1.0, 2.0, or 3.0%). The diets were fed to fingerling Nile tilapia (10.5 ± 0.5 g) at a daily rate of 4% of their body weight, three times a day, for 60 days. Except the lymphocytes and monocyte numbers in fish fed SB, hematological parameters, including red blood cell (RBC) hematocrit (Ht), hemoglobin (Hb), and white blood cells (WBC) were not significantly (P > 0.05) affected by dietary Biogen and SB. The lymphocytes number in Nile tilapia fed on SB increased with increasing SB up to 2% level, and decreased afterwards. Monocyte numbers showed irregular patterns. The activities of serum enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST) of fish fed diets containing Biogen or SB were not significantly affected by dietary treatments (P > 0.05). No structural differences of tilapia liver were detected between all Biogen treatments and sodium butyrate concentrations up to 1% with control. At concentrations of 2 and 3% sodium butyrate, liver steatosis increased leading to shrinked acentric nuclei. At a concentration of 2% Biogen, some glomerulus cells had fading cytoplasm. Concerning fish fed SB diets, the structure of kidney was the same as in control except at concentration of 3% SB, where the septum between cells disappeared. No changes in gill structure were noticed at all concentrations of Biogen and SB.

Evaluation of different hydroponic media for mint (Mentha arvensis) with common carp (Cyprinus carpio) juveniles in an aquaponic system

Abstract: Three hydroponic media crushed stones (T1), river stones (T2), and floating raft (T3) were compared in an aquaponic system with common carp (Cyprinus carpio) and mint (Mentha arvensis). Fish effluents were used as plant nutrients while plants filtered water by stripping off the nutrients before returning to the fish tank. Fish growth, plant growth, and water quality parameters were used to evaluate the suitability of three different media. Growth performance of common carp and mint followed the relationship of crushed stones > floating raft > river stones with significant difference observed among all treatments. Total ammonia nitrogen (TAN) removal varied significantly among different treatments. The maximum TAN removal was observed in T1 (77.13%) followed by T3 (69.65%), and the minimum removal was observed in T2 (48.82%). Nitrate removal varied significantly among different treatments. The highest removal was observed in T1 (82.95%) followed by T3 (68.04%) and T2 (59.51%). Removal of phosphate was significantly lower in T2 (50.12%) when compared to T1 (67.85%) and T3 (70.71%). Biofilter performance (g m−3 day−1) of T2 (4.80) was significantly lower compared to T1 (7.13) and T3 (7.37). Crushed stone and floating raft were significantly efficient when compared to river stone medium in terms of nutrient removal and water quality maintenance for the fish culture. Considering all growth parameters, crushed stone media proved to be better when compared to other two media. Thus, medium selection could be a considerable factor when designing an aquaponic system.

Aquaculture in the German print media

Abstract: The current aquaculture methods are criticized by the public for potentially causing ecological problems and health risks for consumers. An unfavorable public perception may lead to a decline in consumption. Also the production might be affected negatively since legislation and as such approval procedures are influenced by public perception. The aquaculture industry has to consider public reactions to their production practices in order to prosper further. One way to learn about and to understand public perception is the analysis of media coverage since media are an important source of information for the public. Thus, the media coverage of an issue reveals potential points of conflict between the aquaculture sector and the public. We aimed to identify which attitude the media adopted toward aquaculture as a news issue and to determine which aspects of aquaculture were highlighted and how they were discussed. The study also focused on the presentation of recirculating systems and of organic aquaculture. Using this approach, we analyzed the media coverage of aquaculture in the most widely read German newspapers in the time period from 2008 to 2013. A mixture of qualitative and quantitative content analysis was used to examine the coverage in the Suddeutsche Zeitung, the Frankfurter Allgemeine Zeitung and the BILD. Our results indicate that the analyzed media primarily reported on aquaculture in a positive to neutral tone. Economic benefits of aquaculture dominated the coverage, whereas potential negative aspects of aquaculture received less attention. Organic fish farming and closed recirculating systems were both presented as eco-friendly practices. The German aquaculture sector was described as being sustainable and practicing good management.

Effects of feeding frequency and Spirulina on growth performance, skin coloration and seed production on kenyi cichlids (Maylandia lombardoi)

Abstract: Kenyi cichlids belong to mbuna group which is specific to Lake Malawi. Gender discrimination is easy because males have yellow, females have blue colors and their spawning efficiency is good. Cichlid producers prefer kenyi cichlids in recent years due to reproduction performance and coloring of kenyi. In this study, effects of Spirulina-based diet and feeding frequency on coloration, seed production, growth and survival on kenyi cichlids (Maylandia lombardoi) were investigated for 112 days. The study was carried out in a recirculating system which has 100 L each tank and 12 fiberglass tanks with three replicates. Ten fish (3 months old, mean body weight 2.00 ± 0.05 g and mean total length 4.51 ± 0.42 cm) were randomly placed in each tank. Experimental groups were designed with commercial granule (C) and commercial granule Spirulina (S) feeds. In the present study, two feeding frequencies were applied: one feeding daily at 09:00 (namely C1, S1) and three times daily at 09:00, 12:00 and 17:00 (namely C3, S3). The growth and seed production of cichlid fed three times daily were significantly higher compared to fish fed one feeding daily, irrespective of feed source (P < 0.05). Moreover, the specific growth rate of cichlid fed Spirulina-based diet was significantly elevated compared to fish fed non-Spirulina-based diet. The Spirulina-based diets affected skin coloration giving a bluish hue and a typical chroma values for the females of kenyi cichlid. In conclusion, growth performance, seed production and skin coloration of kenyi cichlid fed Spirulina diets three times daily enhanced under the study condition.

Evaluation of suitability of wastewater-grown microalgae (Picochlorum maculatum) and copepod (Oithona rigida) as live feed for white leg shrimp Litopenaeus vannamei post-larvae

Abstract: The present work deals with the growth efficiency of Picochlorum maculatum and Oithona rigida in shrimp-cultured wastewater. In addition, the effects of wastewater (WW)-cultured P. maculatum and O. rigida on the growth and survival of Litopenaeus vannamei post-larvae (PLs) was studied and the results were compared with artificial culture media (ACM)-cultured P. maculatum and natural seawater (NSW)-cultured O. rigida. The results revealed that the high density obtained in microalgae and low in copepod using wastewater as a medium. Further, shrimp PLs fed with WW-cultured microalgae, and NSW-cultured copepod had specific growth rate and higher survival, but it was not significantly different (p > 0.05) from PL fed on ACM-cultured microalgae and WW-cultured copepod, indicate that P. maculatum has potential to be used as live feed for the hatchery rearing of L. vannamei PLs, in replacing microdiet. Further study is needed on optimization of wastewater-cultured copepod as a live feed to yield maximum growth and survival.

Research on China’s mariculture efficiency evaluation and influencing factors with undesirable outputs—an empirical analysis of China’s ten coastal regions

Abstract: 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.

Probiotic bacteria (Lactobacillus plantarum) expressing specific double-stranded RNA and its potential for controlling shrimp viral and bacterial diseases

Abstract: We engineered probiotic bacteria, Lactobacillus plantarum, to produce specific double-stranded (ds)RNA for viral inhibition in penaeid shrimp. When supplemented in feed, the developed strain should offer specific viral disease resistance and still remain other beneficial effects on shrimp health against other bacterial pathogens. The pWH1520 expression vector was constructed to encode hairpin RNA targeting shrimp yellow head virus (YHV) in L. plantarum. The quantity of YHV-specific dsRNA (dsYHV) was approximately 1.66 ± 0.25 ng from 7 × 1011 CFU of L. plantarum. Feeding shrimp with the probiotic expressing dsYHV (at 1011 CFU g−1 feed) for 5 days prior to YHV challenge provided shrimp partial protection against YHV. In vitro agar well diffusion analysis revealed that both wild-type and transformed L. plantarum inhibited growth of Vibrio parahaemolyticus, the shrimp pathogen responsible for acute hepatopancreatic necrosis disease (AHPND) and early mortality syndrome (EMS). When tested in shrimp by immersion method, both L. plantarum strains (at 107 CFUs ml−1 seawater) also provided shrimp protection against V. parahaemolyticus. In conclusion, this study suggested the potential of the dsRNA-expressed L. plantarum for promoting shrimp health against the pathogenic virus. In addition, engineering L. plantarum for dsRNA production did not alter the probiotic’s intrinsic antibacterial property, and therefore, the developed strain can be used to protect shrimp against the important bacterial pathogen, V. parahaemolyticus causing AHPND/EMS.

The beneficial effects of multispecies Bacillus as probiotics in enhancing culture performance for mud crab Scylla paramamosain larval culture

Abstract: Mud crabs (Scylla) are promising aquaculture crustaceans due to their fast growth and good market demand. High rates of larval mortalities associated with bacterial diseases in hatcheries are one of the major obstacles to the growth of Scylla aquaculture. Currently, antibiotics are used extensively in Scylla larval culture to improve survival rate, but its use poses numerous risks. The aim of this study was to determine the culture performance of Scylla paramamosain larvae with the use of a probiotic, namely a multispecies Bacillus, at various concentrations. In this study, the effects of Bacillus spp. were tested in three trials. There were higher average larval survivals in treatments with a multispecies Bacillus probiotics added compared with the control, especially at concentrations of 1.00 × 104 (12.33–18.33 ± 1.76–3.76 % compared to 1.67–3.67 ± 1.67–1.76 %; P < 0.05) and 2.00 × 104 cfu/ml. This was significantly lower than the control (1.33 ± 1.33 cfu/ml compared to 32.67 ± 11.05 cfu/ml) during the later days post-hatching. Green colonies Vibrios are known to be pathogenic to Scylla larvae, and thus lower numbers are desirable in culture. The recommended concentration of the multispecies Bacillus to be added into S. paramamosain larvae was therefore 1.00 × 104 and 2.00 × 104 cfu/ml (0.50 and 1.00 g/50 l, respectively). The use of Bacillus as a probiotic is an ideal alternative to antibiotics in Scylla hatcheries to provide a consistent, commercially feasible production of seedlings.

Acute toxicity and anaesthetic effect of clove oil and eugenol on Siamese fighting fish, Betta splendens

Abstract: With brilliant colouration and long, flowing fins, the Siamese fighting fish (Betta splendens) is one of the most popular species of freshwater aquarium fish. In the ornamental Siamese fighting fish business, stress is one of the major causes of fish injury, including collapse of the fins. This problem could be solved by using anaesthetic treatment. Clove oil and eugenol were investigated for acute toxicity, which was determined using an aqueous dilution method at concentrations ranging from 0 to 35 mg L−1. Based on a criterion of fish transportation within 2 days, induction times of anaesthesia, fish behavioural responses and mortality, and recovery times were monitored and recorded over a 48-h period. The 48-h LC50 of clove oil and eugenol was 30.63 [with a 95 % confidence interval (CI) of 29.23–32.10 mg L−1] and 29.95 mg L−1 (with a 95 % CI of 28.50–31.48 mg L−1), respectively. Concentrations of 10 and 15 mg L−1 clove oil over a 48-h period induced a sedative effect, resulting in partial loss of reactivity and mobility while maintaining equilibrium. At these concentrations, the fish could recover behaviourally within 3–5 min. Recovery times decreased with lower doses and shorter exposure times. The higher the concentration of either clove oil or eugenol used, the lower the concentrations of total ammonia and un-ionized ammonia that were detected. This study revealed that clove oil and eugenol are highly effective anaesthetic agents as a transportation mixture for Siamese fighting fish.

In vitro screening of lactic acid bacteria isolated from gastrointestinal tract of Atlantic Salmon (Salmo salar) as probiont candidates

Abstract: A total of 20 lactic acid bacteria (LAB) were isolated from the gastrointestinal tracts of Atlantic salmon (Salmo salar) and screened for antimicrobial activity against six fish pathogens using either a microtiter plate assay or a well diffusion assay. The results indicated that three LAB exhibited antimicrobial activity against at least two pathogens. Based on their partial 16S ribosomal deoxyribonucleic acid (16S rDNA) sequences, these isolates were identified as Lactobacillus farraginis, Pediococcus acidilactici, and P. pentosaceus. In addition, these LAB were able to tolerate the simulated gastrointestinal tract conditions (stomach and intestine), had a good adhesion capacity to intestinal mucus as well as were able to grow in intestinal mucus of Atlantic salmon. These results suggest that these LAB are potential probionts in aquaculture. However, further studies are required to evaluate probiotic properties in aquatic animals.

Influence of low molecular weight chitooligosaccharides on growth performance and non-specific immune response in Nile tilapia Oreochromis niloticus

Abstract: A 50-day feeding trial was conducted to evaluate the effects of five different levels of low molecular weight chitooligosaccharides (LMW-COS) (0, 0.1, 0.2, 0.4, and 0.8 g kg−1) on growth performance, serum parameters, body composition, and non-specific immunity in Nile tilapia (Oreochromis niloticus). A total of 600 fish were divided into 5 treatments with 4 replicates of 30 fish per tank. The results showed that dietary supplementation with 0.4 or 0.8 g kg−1 COS significantly improved the final body weight, specific growth rate, feed efficiency rate, and protein efficiency ratio of fish (P 0.05). In one word, the supplementation of 0.4 and 0.8 g kg−1 COS significantly increased the growth performance and non-specific immunity of Nile tilapia; the recommended COS supplementation in diet is 0.4 g kg−1 diet.

Financial viability of inserting the biofloc technology in a marine shrimp Litopenaeus vannamei farm: a case study in the state of Pernambuco, Brazil

Abstract: This study analyzed the financial viability of inserting the biofloc technology (BFT) system and maintaining the conventional culture system for the marine shrimp Litopenaeus vannamei in a farm located in the state of Pernambuco, northeastern Brazil. To obtain information related to investment and operating costs, we used three ponds (625 m2 each) covered with high-density polyethylene operating with the BFT system and data from three conventional ponds (2.86 ha each) used in a farm during 2014. The total production costs of BFT were eight times higher than the conventional system. Operating profit and profitability index were US$ 51,871.54 ha−1 year−1 and 30.22 % for BFT, and US$ 21,523.83 ha−1 year−1 and 59.79 % for the conventional system, respectively. In investment analysis, indicators were favorable for both systems, with greater expressiveness of the net present value (NPV) for the BFT (US$ 142,004.42) and internal rate of return (IRR) 4.5 times higher for conventional system (131.86 %). To achieve favorable results of profitability and viability, combined with the ability to contribute to the sustainable development of marine shrimp farming, the BFT system is a promising alternative to replace traditional systems used in northeastern Brazil.

Environmental assessment of the impact of cage fish farming on water quality and phytoplankton status in Monastir Bay (eastern coast of Tunisia)

Abstract: Although aquaculture development is experiencing a rapid growth on the southern Mediterranean shore, studies of its environmental impact are still limited. This study, conducted from January to December 2014, in and around a cage fish farm located in Monastir Bay (eastern coast of Tunisia), investigated the hypothesis that cage fish farming would affect the water column quality and plankton communities. Phytoplankton diversity in addition to 13 physico-chemical parameters and chlorophyll-a were all investigated at 11 experimental stations located inside and around the farm. A total of 106 phytoplankton taxa were identified at genus and/or species level, and assigned to two major (dinoflagellates and diatoms) and four minor (cyanobacteria, euglenophyceae, coccolithophorides, and dictyophyceae) groups, with a remarkable predominance of heterotrophic and mixotrophic species, in particular among dinoflagellates taxa, highlighting a top-down model of phytoplankton regulation. Across seasons, a high Shannon-Wiener diversity index (H′) was recorded. Further, we have demonstrated that nutrients were the most important factors contributing to differences in species abundance, as revealed by N/P and Si/Pi ratios that were factors most affecting phytoplankton distribution. Our findings revealed that fish farming aquaculture became an additional source of nutrients in the bay. In some stations, nutrient loading has little or no trophic impact, while, at others, there is evidence that nutrients are assimilated by primary producers. Our study provides a rich information platform for conservation strategies of the bay of Monastir.

Interaction effects of dietary lipid and lysine on growth feed utilization and body composition of juvenile grass carp (Ctenopharyngodon idella)

Abstract: 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). 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.

Seasonal distribution, sources and sink of dissolved organic carbon in integrated aquaculture system in coastal waters

Abstract: Dissolved organic carbon (DOC) concentrations were measured in the Sanggou Bay (SGB) in northern China, in order to investigate the seasonal distribution, sources and sink of DOC in an integrated multi-trophic aquaculture (IMTA) system of fish, shellfish and seaweed. The sampling was conducted during April (spring), August (summer), October (autumn) and January (winter) of 2011–2012. Salinity, Chlorophyll a (Chl a) and DOC showed large spatial and seasonal variation during sampling period. DOC increased with increasing Chl a in spring, summer and autumn and decreased with increasing salinity in summer compared to other seasons. Maximum surface concentration of DOC ranged from 108.0 to 875.2 µM and minimum from 134.4 to 184.7 µM was found during summer and spring, respectively. Terrestrial input, phytoplankton and seaweed were the main sources of DOC in SGB. Shellfish farming area was enriched in organic matter as well as served to reduce DOC levels in the bay. As it was indicated that average annual removal of 42 % DOC occurred in the shellfish, the lowest occurred at an average 32 % in combined shellfish and seaweed culture area. Additionally, controlled experiment results showed that seaweed produced approximately 64.81 ± 40.86 µM day−1 and shellfish generated approximately 13.36 ± 6.07 µM day−1 and assimilated 17.07 ± 13.12 µM day−1 DOC in SGB. Accumulation of DOC at the bottom could be a result of long-term aquaculture activities in the bay. Integration of sea cucumber into IMTA system could be useful to mitigate the stockpile of organic matter at the bottom.