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Microbial community dynamics in semi-commercial RAS for production of Atlantic salmon post-smolts at different salinities

Published on 28/3/2017
Publication date: Available online 20 October 2016
Source:Aquacultural Engineering

Author(s): Ingrid Bakke, Ann Louise Åm, Jelena Kolarevic, Trine Ytrestøyl, Olav Vadstein, Kari Johanne Kihle Attramadal, Bendik Fyhn Terjesen

Fish live in close contact with microbes in their surrounding water. For cultivated marine fish larvae, stable microbial environments, characterized by slow-growing, K-selected bacteria, have been found to improve growth and survival. Compared to flow-through systems, recirculating aquaculture systems (RAS) offer a better possibility for obtaining microbial stability in the rearing water. However, the microbial ecology in RAS is complex and little studied, and to optimize the microbial water quality more knowledge is needed on microbial community dynamics and interactions between microbes and fish. In the present study we investigated microbial community dynamics in three large-scale RAS, operated with different salinities (12, 22 and 32ppt), for production of Atlantic salmon post-smolts. We focused on the stability of microbial communities over time in the bioreactors and the fish tanks, and compared the microbial communities within and between the three RAS. The study showed that: 1) The microbial community of the water was similar between the compartments of each RAS at the same time point, 2) The microbial communities of the water (and to a lesser extent the biofilm) within each system underwent large changes over time, 3) The microbiota of biofilm and water differed significantly within each system, 4) Biofilm community profiles were more similar between RAS than the water community profiles, and 5) Salinity structured the microbial community composition. The present study provides new knowledge on how the microbiota in RAS varies with time and how it is influenced by environmental factors.





Numerical simulation of deformations and forces of a floating fish cage collar in waves

Published on 28/3/2017
Publication date: September 2016
Source:Aquacultural Engineering, Volume 74

Author(s): Xiao-Hua Huang, Gen-Xi Guo, Qi-You Tao, Yu Hu, Hai-Yang Liu, Shao-Min Wang, Shuang-Hu Hao

The dynamic behavior of a fish cage collar in waves was investigated using a numerical model based on the finite element method. The floating collar and mooring system were divided into a series of line segments modeled by straight massless model segments with a node at each end. To verify the validity of the numerical model, research data from other authors were cited and compared with the simulated results, the comparison of results showed a good agreement. The numerical model was then applied to a dynamic simulation of a floating cage collar in waves to analyze its elastic deformation and mooring line tension. The simulated results indicated that the greatest deformation of the collar taken place in the position of the mooring line connection point when incident waves were in the same direction. An increase in the length of mooring line would help to decrease the mooring line tension of the collar. Furthermore, the effects of collar dimension, including collar circumference, pipe diameter in cross-section, and pipe thickness, on the dynamic behavior of the floating collar were discussed. The results of this study provided a better understanding of the dynamic behavior of the fish cage collar.





The composition of readily available carbon sources produced by fermentation of fish faeces is affected by dietary protein:energy ratios

Published on 28/3/2017
Publication date: May 2017
Source:Aquacultural Engineering, Volume 77

Author(s): Carlos O. Letelier-Gordo, Bodil K. Larsen, Johanne Dalsgaard, Per Bovbjerg Pedersen

Fish solid waste (faeces) produced in recirculated aquaculture systems (RAS) might be used for on-farm, single-sludge denitrification if transformed into soluble organic carbon substances. The current study investigated the effect of feeding diets with increasing protein to energy ratios (P:E_15, 17, 19, 21 and 23g/MJ) to rainbow trout (Oncorhynchus mykiss) on the production of volatile fatty acids (VFAs) and ethanol during 7days fermentation of the produced fish faeces. The total yields of VFAs and ethanol obtained (expressed as chemical oxygen demand (COD)) ranged between 0.21–0.24gCOD/gTCOD, showing no differences between treatments. However, the type and quantities of individual VFAs and ethanol changed according to the dietary treatment. Lower P:E ratio diets resulted in higher production of butyric acid and ethanol, whereas higher P:E ratio diets resulted in an increased production of acetic and valeric acid. Changing the diet composition thus affects the composition of readily available carbon that can be derived from the faeces. This can be applied to enhance on-farm single sludge denitrification and reduce the need for adding external carbon sources such as e.g. methanol.

Graphical abstract






Effects of feeding a fishmeal-free versus a fishmeal-based diet on post-smolt Atlantic salmon Salmo salar performance, water quality, and waste production in recirculation aquaculture systems

Published on 28/3/2017
Publication date: September 2016
Source:Aquacultural Engineering, Volume 74

Author(s): John Davidson, Frederic T. Barrows, P. Brett Kenney, Christopher Good, Karen Schroyer, Steven T. Summerfelt

The Atlantic salmon farming industry has progressively decreased the proportion of fishmeal used in commercial diets due to rising costs and sustainability concerns. A variety of alternate proteins have been identified to partially replace fishmeal; however, very little research has described the effect of feeding alternate protein, fishmeal-free diets to Atlantic salmon, particularly post-smolts cultured in recirculation aquaculture systems (RAS). Therefore, a 6-month study was conducted to compare the effects of feeding a fishmeal-free diet (FMF) versus a fishmeal-based diet (FM) on post-smolt Atlantic salmon performance, water quality, and waste production rates in six replicated RAS. Experimental diets were fed to Atlantic salmon (281±5g to begin) in triplicate RAS. Protein ingredients used in the FMF diet included mixed nut meal, poultry meal, wheat flour, and corn protein concentrate; while the FM diet contained menhaden meal, poultry meal, soy protein concentrate, and blood meal proteins. Fish oil derived from whiting fish trimmings was used in the FMF diet to establish a wild fisheries input to farmed fish output ratio of 0:1; while menhaden oil was the primary lipid source for the FM diet. Both diets were formulated with approximately 42% crude protein and 27% crude fat. Each RAS was operated with flushing rates that created an average system hydraulic retention time of 20 days (5% system volume flushed daily) and a mean feed loading rate of 3.2kg feed/m3 of daily make-up water volume. Atlantic salmon growth, survival, and feed conversion ratios (FCR) were unaffected (P >0.05) by diet. At the conclusion of the study, Atlantic salmon fed the FMF and FM diets were 1.716±0.076 and 1.720±0.065kg; cumulative survival was >99% for both; and average FCR was 0.89±0.03 and 0.90±0.02, respectively. The FMF diet resulted in greater total phosphorous (TP), carbonaceous biochemical oxygen (cBOD), and total suspended solids (TSS) mass per kg feed in the effluent (P <0.05). The FMF and FM diets produced 0.009±0.001 v. 0.006±0.001kg TP/kg feed; 0.079±0.005 v. 0.056±0.005kg cBOD/kg feed; and 0.297±0.028 v. 0.221±0.032kg TSS/kg feed, respectively. A significantly higher percentage of TSS was captured by radial flow settlers of RAS receiving the FMF diet compared to capture by settlers associated with the FM diet. Mass balance data, radial settler removal efficiency, and observations of flushed solids suggested that the FMF diet produced fecal matter with better settling characteristics. Lower TSS and true color values (P <0.05), indicative of clearer water, were measured in RAS receiving the FMF diet. Total phosphorous (most of which was dissolved) was 4 times greater in the culture water of RAS that received the FMF diet, e.g., 4.3±0.1mg/L v. 0.9±0.0mg/L for the FM Diet. This was the first research attempt to formulate a fishmeal-free diet for Atlantic salmon with this ingredient profile and one of few studies to demonstrate uncompromised Atlantic salmon performance when feeding a diet without fishmeal.





Comparing clear-water RAS and biofloc systems: Shrimp (Litopenaeus vannamei) production, water quality, and biofloc nutritional contributions estimated using stable isotopes

Published on 28/3/2017
Publication date: May 2017
Source:Aquacultural Engineering, Volume 77

Author(s): Andrew J. Ray, Thomas H. Drury, Adam Cecil

Indoor shrimp aquaculture systems can be used to produce fresh, never-frozen, quality shrimp near metropolitan seafood markets regardless of season and climate. However, questions still remain regarding what type of production system is best suited to maximize indoor production. In this project, two types of systems were compared: clear-water (CW) RAS and biofloc (BF) systems. Three, 1.36m3 tanks were assigned to each of the two treatments; CW tanks had external settling chambers, two foam fractionators, and external biofilters, all operated continuously. BF tanks had settling chambers and one foam fractionator which were operated as needed to control solids accumulation. Shrimp weighing 0.42g were stocked in all tanks at 250m−3 and grown for 55 days. Ammonia and pH levels were significantly (P<0.05) higher in the CW treatment, while nitrite, nitrate, and turbidity were all significantly higher in the BF treatment, although all parameters remained within acceptable ranges for shrimp growth. Shrimp mean harvest weight was significantly higher, biomass (kgm−3) was significantly greater, and FCR was significantly lower in the CW treatment; there were no significant differences in survival between treatments. Isotope levels indicated that shrimp in the BF treatment obtained a portion of the C (18-60%) and N (1-18%) in their tissues from biofloc material; however, this effect did not positively influence production in that treatment. By nearly eliminating solids from the water and using an external biofilter, substantially better water quality was maintained in the CW systems, which may have been a major contributor to the improved shrimp production in that treatment.





Hatchery performance of the pacific white shrimp in biofloc system using different stocking densities

Published on 28/3/2017
Publication date: November 2016
Source:Aquacultural Engineering, Volume 75

Author(s): Marco Antonio de Lorenzo, Moisés Angel Poli, Efrayn Wilker Souza Candia, Delano Dias Schleder, Marysol Santos Rodrigues, Ariane Martins Guimarães, Walter Quadros Seiffert, Felipe do Nascimento Vieira

Higher rates of production per unit area, avoiding or minimizing significant environmental damages, is a challenge for aquaculture to contribute with an ascendant demand for food due to the increase in world population. The present study assessed the hatchery performance of Litopenaeus vannamei between the mysis 1 and postlarva 5 stages, in a zero-exchange biofloc system under 12.5:1 fixed C:N ratio with dextrose in four stocking densities: 200, 250, 300 and 350 larvae per liter (D200, D250, D300, D350 respectively). Water quality and performance parameters were compared among treatments. The mean values of the evaluated water quality parameters were appropriate for this production stage in all treatments. Fertilization with dextrose efficiently controlled ammonia levels not reaching the average concentrations considered toxic for the specie. Lower values of pH and higher values of volatile solids were finding in D350. There was no difference between groups in means of survival and dry weight of postlarva 5. Therefore, the use of biofloc systems without water exchange with dextrose as a carbon source in 12.5:1C:N ratio resulting in adequate production indexes and water quality during the mysis 1 to postlarva 5 hatchery phase of L. vannamei. Based in these results the density limit to a viable BFT hatchery was not reached.





Effects of different substrates on settlement and growth of pearl oyster (Pinctada maxima) larvae in hatcheries

Published on 28/3/2017
Publication date: May 2017
Source:Aquacultural Engineering, Volume 77

Author(s): Qingheng Wang, Junhui Li, Feilong Liang, Shaohe Xie, Xiaodong Du, Yuewen Deng

Metamorphosis of pearl oyster Pinctada maxima pediveliger is affected by physical and chemical characteristics of the collectors. In the present study, we conducted four experiments to evaluate the effects of collector characteristics on the settlement and growth of hatchery-reared pearl oyster. In the first experiment, black, red, yellow, and white plastic sheets were used as collectors. Settlement of P. maxima larvae in black and red plastic sheets was significantly higher than that in yellow and white plastic sheets (P <0.05). Mean shell length was not significantly different among the four colored sheets (P >0.05). In the second experiment, pediveliger larvae were settled onto palm rope and polypropylene rope collectors. The number of spat in the palm rope collector was significantly higher than that of spat in the polypropylene rope collector (P <0.05). Mean shell length was not significantly different between palm rope and polypropylene rope collectors (P >0.05). In the third experiment, settlement and subsequent growth were compared between plastic sheets with and without biofilm. The number of spat in the plastic sheets with biofilm was significantly higher than that in the plastic sheets without biofilm (P <0.05). Mean shell length after settlement were not significantly affected (P >0.05). In the fourth experiment, pediveliger larvae were stored in tanks with (experimental group) and without collectors (control group). The settlement rate of larvae on the wall was not significantly different between the two groups(P> 0.05). The settlement rates of the larvae on the wall and collectors in the experimental group were significantly larger than those on the wall in the control group(P <0.05). Mean shell length was not significantly different between the groups (P >0.05). Our results suggest that appropriate selection of collector types, color, and conditioning can improve the settlement of P. maxima larvae in hatcheries.





IFC - Editorial Board

Published on 28/3/2017
Publication date: September 2016
Source:Aquacultural Engineering, Volume 74









The effects of different feeding rates and re-feeding of Litopenaeus vannamei in a biofloc culture system

Published on 28/3/2017
Publication date: May 2017
Source:Aquacultural Engineering, Volume 77

Author(s): Gabriele Lara, Bárbara Hostins, Aline Bezerra, Luís Poersch, Wilson Wasielesky

The natural productivity in biofloc culture systems could be an important source of supplementary food to shrimp, representing savings in artificial feed. The aim of the present study was to evaluate the effects of using different feeding rates for a period of 21days with a posterior re-feeding period in a microcosm system in the presence of bioflocs. Litopenaeus vannamei juveniles (1.14±0.38g) were stocked at 400 shrimp m−3 in 150-L tanks in a biofloc recirculation system in two phases. The feeding rates were calculated considering an expected weekly growth of 1g week−1 and an estimated weekly mortality of 0.5%; each treatment corresponded to a different feeding rate, and each feeding rate corresponded to a fixed food conversion ratio. The first phase (food restriction) lasted 21days, and the following treatments were used: T0 (no artificial feed addition), T0.3, T0.6, T0.9, T1.2, T1.5, T1.8 and T2.1. In the second phase (re-feeding), the feeding rate was calculated based on the average of the best results in the first phase of the experiment (FCR=1.45). The re-feeding period lasted for more 29days. There were no observed significant differences in the water quality parameters among the treatments (P>0.05). At the end of the food restriction, the shrimp in T0, T0.3 and T0.6 presented lower final weights (P<0.05), and the weights in the other treatments did not significantly differ (P>0.05). The survival rate was lower only in T0 in the two phases of the study. The other treatments presented survival rates higher than 95%, with no significant differences among them. The feed intake did not increase during the re-feeding period, indicating that hyperphagia did not occur after a period of food restriction. The SGRs were higher for treatments that received lower amounts of feed in the first phase, and treatments T0, T0.3 and T0.6 presented partial weight compensation compared with the treatments with higher feeding rates. This study indicates that shrimp can be reared in a biofloc system with lower feeding rates, obtaining partial weight compensation and high survival rates and saving up to 24.79% of the artificial feed.





Comparative adsorption evaluation of biochars from paper mill sludge with commercial activated carbon for the removal of fish anaesthetics from water in Recirculating Aquaculture Systems

Published on 28/3/2017
Publication date: September 2016
Source:Aquacultural Engineering, Volume 74

Author(s): Catarina I.A. Ferreira, Vânia Calisto, Marta Otero, Helena Nadais, Valdemar I. Esteves

Tricaine methanesulfonate (MS-222), benzocaine and 2-phenoxyethanol (2-PE) are widely used in intensive aquaculture systems to control stress during handling and confinement operations. This work aimed to study the adsorptive removal of these anaesthetics from water, comparing two waste-based adsorbents produced by pyrolysis of paper mill sludge with a commercial activated carbon. The use of commercial activated carbon resulted in maximum adsorption capacities of 631, 435 and 289mgg⿿1 for MS-222, benzocaine and 2-PE, respectively (obtained by the fitting of Langmuir-Freundlich model), which are between 4 and 8 times higher than those determined for the alternative adsorbents. Even so, the obtained results point to the promissory utilization of these waste-based adsorbents in Recirculating Aquaculture Systems, as an integrated way of managing such residues and treatment of aquaculture waters contaminated with anaesthetics.





Development of an innovative ring-shaped cultivation system for a land-based cultivation of marine macroalgae

Published on 28/3/2017
Publication date: May 2017
Source:Aquacultural Engineering, Volume 77

Author(s): Stefan Sebök, Werner B. Herppich, Dieter Hanelt

Marine macroalgae become increasingly important as a regenerative source of biomass for the production of food, pharmaceuticals, cosmetics and energy. An increasing and environmentally sound utilization of algae requires a closed, land-based cultivation, not limited to coastal or offshore areas. Within this study, segmental and ring-shaped cultivation vessels were developed and compared to tumble cultivation in a circular tank. The development of these innovative approaches also considered economic efficiency, adaptability, handling and reliability. The growth rates achieved by cultivating the red algae P. palmata and C. crispus and the green alga U. lactuca over a test period of 7 d were used to evaluate these experimental models. Mean growth rates of P. palmata and C. crispus in the ring-shaped cultivation model were slightly decreased whereas growth rate of U. lactuca was similar or increased compared to tank cultivated algae. The developed ring-shaped cultivation system distinctly lowered variable costs by reducing the necessary volume of cultivation medium. An increased control of the cultivation process was achieved by separating the supply of CO2 and nutrients, and the temperature control from agitation.





Influence of feeding sequence, light and colour on the performance of a self-grading system designed for turbot (Scophthalmus maximus)

Published on 28/3/2017
Publication date: May 2017
Source:Aquacultural Engineering, Volume 77

Author(s): Mirko Bögner, Sarah Zwicker, Desislava Bögner, Matthew J. Slater

Grading of cultured flatfish is essential to maintain even sizes and to avoid potential feeding dominance or cannibalism. Current hand-grading and forced mechanical grading methods result in labour costs and additional stress to animals, reducing their growth performance. This study tested a self-grading system allowing turbot (Scophthalmus maximus) to self-grade, based on size, between tank sections within 8000L tanks designated as “Graded (G)” and “Non-Graded (NG)”. The grading success (percentage of graded animals/total gradable individuals) with stimuli (light, feeding sequence and colour of the grading device) and without stimuli was analyzed over 9days. Mean grading success without stimuli was 38.1±11.5%. Grading success was not improved by changes in feeding sequence (30.6±10.2%) or altered colour of the grading device (30.9±13.8%). Marked increases in grading success were obtained by adding a light source to the G section (52.9±12.4%), and by combining the presence of a light source and the feeding sequence (57.9±14.4%). The combination of light sources and changes to the colour of the self-grading device resulted in the highest mean grading success (72.1±18.2%) overall. Light and colour stimuli combined yielded the highest self-grading maximum (88.36±5.3%), achieved on day 6 after experimental onset. A three-parameter asymptotic exponential equation was fitted to the data from each stimulus and parameters describing the curves of all conditions are reported. The present results indicate that the tested self-grading systems for turbot can be highly efficient if used with the appropriate stimuli. Self-grading systems operating at the measured levels of success offer a viable alternative to stressful grading events, avoiding significant commercial disadvantages as well as improving animal welfare and performance.





Time-dependent reliability analysis of mooring lines for fish cage under corrosion effect

Published on 28/3/2017
Publication date: May 2017
Source:Aquacultural Engineering, Volume 77

Author(s): Hui-Min Hou, Tiao-Jian Xu, Guo-Hai Dong, Yun-Peng Zhao, Chun-Wei Bi

Moored fish cage structures are forced to move into the offshore area due to the shrinking availability of sheltered near-shore sites and increasing environmental impacts of aquaculture, and this provokes a significant challenge for the reliability design of mooring system. The uncertainties involved in the predictions of applied loads and structural strength are analyzed for calculating the reliability level of mooring system. In this study, a probability corrosion model is used to describe the uncertainty of corrosion depth and the joint probability density of significant wave height and spectral peak period is selected to depict the randomness of sea states. The non-linear finite element model is developed to investigate the minimum breaking strength of mooring chains and is validated through comparing with the formulas providing by the International Association of Classification Societies (IACS) Unified Requirements concerning for Materials and Welding. A validated numerical model is applied to calculate the tension force of mooring system for both the single-cage system and the multi-cage system at several sea states, and the response surface method is utilized to display the limit state function to calculate the reliability level in terms of the uncertain metocean variables. The results indicate that the reliability level decreases significantly with the increasing corrosion depth and the correlation of corrosion model for mooring chains has a remarkable impact on the failure probability of mooring system. In addition, the failure probability of mooring system for the four-cage system is much higher than that for the single-cage system.





Floating faeces: Effects on solid removal and particle size distribution in RAS

Published on 28/3/2017
Publication date: Available online 31 October 2016
Source:Aquacultural Engineering

Author(s): Mark Schumann, Julia Unger, Alexander Brinker

The removal of solid wastes originating from faecal matter is one of the decisive challenges for future fish farming, in particular given the current emphasis on water reuse in aquaculture. This study compared solid waste removal performance in replicate recirculating systems in which the only difference was the removal concept being deployed. Rainbow trout (Oncorhynchus mykiss) of the test group were fed an innovative diet supplemented with 2.5% cork granules (0.5–1mm) resulting in buoyant faecal casts (density values below 1.00gcm−3). These were removed directly from the tank by a low cost slotted pipe at the water surface. The control group was fed a conventional diet, identical to the experimental feed except that it lacked the cork additive. The resulting solids in both systems were removed by sedimentation in a classic manure pit, which was drained to the drum filter twice a day. Wastewater from both treatments was mechanically cleaned by a drum filter and biologically treated by a moving bed bioreactor before being returned to the tanks. The cork treatment led to a substantially higher solid load being delivered to the drum filter via the wastewater outflow than in the control system. The average removal efficiency of cork-treated wastes was more than twice that achieved in the control system (59% vs. 25%). Total suspended solid (TSS) in the backwash stream of the drum filter was about five times greater in the cork diet treatment. There was no significant difference in the particle size distribution or TSS load of water passing the 100μm gauze of the drum filter in the two systems. Cork supplementation did not affect growth or mortality of rainbow trout. The present study shows that the application of floating faeces is an exciting prospect in recirculating aquaculture systems, offering significant improvements in solid removal efficiency.





Fixed-bed adsorption of Tricaine Methanesulfonate onto pyrolysed paper mill sludge

Published on 28/3/2017
Publication date: May 2017
Source:Aquacultural Engineering, Volume 77

Author(s): Catarina I.A. Ferreira, Vânia Calisto, Marta Otero, Helena Nadais, Valdemar I. Esteves

The removal of Tricaine Methanesulfonate from water in a fixed-bed column packed with pyrolysed paper mill sludge was evaluated for application in Recirculating Aquaculture Systems. Breakthrough adsorption curves were determined for this pharmaceutical, under different operating conditions. In a laboratory-scale approach, with synthetic effluent, a bed adsorption capacity of 125mgg−1 was obtained under a flux of 56Lmin−1 m−2, with 400mgL−1 of MS-222 with 4.5cm bed depth. The performance of the continuous adsorption in a column packed with biological paper mill sludge-based carbon, using real aquaculture wastewater as matrix, was not significantly affected. Then, scale-up was carried out and the bed depth service time model was applied and provided good predictions. Finally, the thermal regeneration of the exhausted adsorbent was assessed, which revealed satisfactory results for one cycle reusability after saturation; however, considering the nature of its precursor, the use of new adsorbent could be more profitable than its regeneration, functioning also as an additional option for the management of such wastes.





Investigating the influence of nitrate nitrogen on post-smolt Atlantic salmon Salmo salar reproductive physiology in freshwater recirculation aquaculture systems

Published on 28/3/2017
Publication date: Available online 5 October 2016
Source:Aquacultural Engineering

Author(s): Christopher Good, John Davidson, Luke Iwanowicz, Michael Meyer, Julie Dietze, Dana W. Kolpin, David Marancik, Jill Birkett, Christina Williams, Steven Summerfelt

A major issue affecting land-based, closed containment Atlantic salmon Salmo salar growout production in water recirculation aquaculture systems (RAS) is precocious male maturation, which can negatively impact factors such as feed conversion, fillet yield, and product quality. Along with other water quality parameters, elevated nitrate nitrogen (NO3-N) has been shown to influence the reproductive development and endogenous sex steroid production in a number of aquatic animal species, including Atlantic salmon. We sought to determine whether elevated NO3-N in RAS can influence early maturation in post-smolt Atlantic salmon in an 8-month trial in replicated freshwater RAS. Post-smolt Atlantic salmon (102±1g) were stocked into six RAS, with three RAS randomly selected for dosing with high NO3-N (99±1mg/L) and three RAS set for low NO3-N (10±0mg/L). At 2-, 4-, 6-, and 8-months post-stocking, 5 fish were randomly sampled from each RAS, gonadosomatic index (GSI) data were collected, and plasma was sampled for 11-ketotestosterone (11-KT) quantification. At 4- and 8-months post-stocking, samples of culture tank and spring water (used as “makeup” or replacement water) were collected and tested for a suite of 42 hormonally active compounds using liquid chromatography/mass spectrometry, as well as for estrogenicity using the bioluminescent yeast estrogen screen (BLYES) reporter system. Finally, at 8-months post-stocking 8–9 salmon were sampled from each RAS for blood gas and chemistry analyses, and multiple organ tissues were sampled for histopathology evaluation. Overall, sexually mature males were highly prevalent in both NO3-N treatment groups by study’s end, and there did not appear to be an effect of NO3-N on male maturation prevalence based on grilse identification, GSI, and 11-KT results, indicating that other culture parameters likely instigated early maturation. No important differences were noted between treatment groups for whole blood gas and chemistry parameters, and no significant tissue changes were noted on histopathology. No hormones, hormone conjugates, or mycotoxins were detected in any water samples; phytoestrogens were generally detected at low levels but were unrelated to NO3-N treatment. Finally, low-level estrogenicity was detected in RAS water, but a NO3-N treatment effect could not be determined. The major findings of this study are i) the NO3-N treatments did not appear to be related to the observed male maturation, and ii) the majority of hormonally active compounds were not detectable in RAS water.





The effect of light intensity on performance of larval pike-perch (Sander lucioperca)

Published on 28/3/2017
Publication date: May 2017
Source:Aquacultural Engineering, Volume 77

Author(s): Moritz Tielmann, Carsten Schulz, Stefan Meyer

In this work performance parameters of larval pike-perch (Sander lucioperca) reared under four different light intensities (100, 500, 1000 and 2500lx) until 21days post hatch (dph) were investigated. As performance parameters change in length and weight, swim bladder inflation, feed consumption, natural mortality, stress induced mortality and RNA-DNA ratio were measured. Aim was to investigate the influence of light intensity on pike-perch performance during the first three weeks of larval rearing. Significant differences were found in natural and stress induced mortality as well as in weight growth. No single light exposure level combined optimal performance of all tested performance parameters. Highest light intensity of 2500lx showed good weight growth but an increase in stress induced mortality. Bright light of 500 and 1000lx intensity was found to improve growth and stress mortality whereas dim light conditions of 100lx showed significantly lower natural mortality. Thus data suggested that most favorable illumination during larval pike-perch rearing comprise a tradeoff between optimal natural mortality under dim light conditions (100lx) or optimal larval growth and stress resistance under bright light conditions (500 and 1000lx). It is shown that high light intensities during larval rearing can be beneficial for pike-perch rearing if offspring supply is not limited.





Application of silver nanoparticles immobilized on TEPA-Den-SiO2 as water filter media for bacterial disinfection in culture of Penaeid shrimp larvae

Published on 28/3/2017
Publication date: September 2016
Source:Aquacultural Engineering, Volume 74

Author(s): Mehrdad Sarkheil, Iman Sourinejad, Maryam Mirbakhsh, Davood Kordestani, Seyed Ali Johari

In the present study, we prepared silver nanoparticles immobilized on silica beads (Ag/TEPA-Den-SiO2) and examined their potential for removing luminous Vibrio sp. Persian1 from seawater used to culture Penaeus (Litopenaeus) vannamei post-larvae. The Ag/TEPA-Den-SiO2 sample was characterized by TEM, FE-SEM/EDS, FT-IR and ICP-OES and its antibacterial activity assayed by a test tube test and flow test using water filters filled with Ag/TEPA-Den-SiO2 as the filter media. The results of the test tube test indicated that no Vibrio sp. Persian1 was detectable after 2-h contact. The filter column that contained Ag/TEPA-Den-SiO2 +silver absorbent inactivated 100% of the bacteria after passage of seawater through the column for 12-h at a flow rate of 0.5l/min. The survival rate and growth performance of post-larvae cultured in seawater treated with an antibacterial filter improved significantly compared with the control.





Pulse versus continuous peracetic acid applications: Effects on rainbow trout performance, biofilm formation and water quality

Published on 28/3/2017
Publication date: May 2017
Source:Aquacultural Engineering, Volume 77

Author(s): Dibo Liu, David L. Straus, Lars-Flemming Pedersen, Thomas Meinelt

Peracetic acid (PAA) products are being introduced to aquaculture as sustainable disinfectants. Two strategies are used to apply PAA: high dose pulse applications, or low dose continuous application. In the present study, their impacts on fish health and water quality were investigated in triplicate flow-through tanks stocked with rainbow trout. The gentler and shorter water cortisol increase measured along twice-per-week pulse applications of 1mgL−1 PAA indicated a progressive adaptation of fish. In contrast, the continuous application of 0.2mgL−1 PAA caused no stress to fish. Meanwhile, no mortality and no impact on growth or innate cellular immunity were observed. The pulse applications restricted biofilm formation, and partially inhibited nitrification. Additionally, the highest oxygen concentration and stable pH were observed. In contrast, the continuous application promoted biofilm formation, and caused a pH increase and intermediate oxygen concentration. The contrast was probably due to different susceptibility of microbes to PAA-induced oxidative stress. To summarize, pulse PAA applications cause minor stress in fish, but have advantages over continuous application by ensuring better water quality.





Development and performance evaluation of sludge remover for intensive aquaculture

Published on 28/3/2017
Publication date: September 2016
Source:Aquacultural Engineering, Volume 74

Author(s): M. Ayub Hossain, Ashoke Kumar Sarker, M. Nurul Amin, M. Mokarrom Hossain, M. Sumon Miah

Fishery is an emerging sector in Bangladesh producing about 3.50 million tons of fish annually of which aquaculture accounts for 2.00 million tons. In intensive aquaculture, pond water gets polluted due to high stocking density and large amount of supplemental feeding results in huge accumulation of unused feed and faeces in the pond bottom. The accumulated bottom sludge depletes dissolved oxygen (DO) and releases harmful gases due to excessive use of chemicals and lack of water exchange facilities. These have negative impact on fish production and economic performance, through disease outbreak, mortality, poor feed conversion ratio (FCR), specific growth rate (SGR) and bad odor in fish muscles. This study was undertaken to develop a sludge remover for cleaning sludge from the intensive fish farming pond and to find the impact of sludge removal on water quality and growth of fish. A sludge remover was developed in Bangladesh Agricultural Research Institute (BARI) which is capable of removing sludge up to 40–50mm from the pond bottom. The main components of sludge remover are a float, axial flow pump (102mm diameter), 7.50kW diesel engine, sludge sucker, crane, propeller, rudder, etc. The discharge of the sludge pump was 14.11L/s. The effective field capacity and field efficiency were 0.078ha/h and 77.23% respectively at the forward speed of 12.5±1.55m/min. The water and sludge ratio was 3.6:1.0 (weight basis). A field trial was carried out to determine the effect of sludge removal on water quality and growth of fishes in intensive cultured ponds. Sludge was removed at three months interval from three pangus-tilapia-carp polyculture ponds. Three ponds of same size and fish stocking were kept as control. Water quality parameters like DO, pH, transparency and, unionized ammonia significantly (p0.05) improved in the sludge removed ponds compare to control ponds. Sludge removed ponds demonstrated better FCR (1.64) and SGR (0.80% per day) compare to FCR (1.90) and SGR (0.71% per day) of control ponds. Fish survival, net yield, net return and BCR (5.40) of sludge removed ponds were higher than those of control ponds. This sludge remover may be recommended for cleaning sludge from intensive cultured fish ponds.





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