ALBERT

Description: Ziel: Bei dem FiT Projekt handelt es sich um ein Entwicklungsvorhaben, welches zum einen die Verbesserung des Transports von lebenden Fischen verfolgt und zum anderen durch einen schonenderen Transport eine verbesserte Wirtschaftlichkeit unter Berücksichtigung der Lebensmittelsicherheit und -qualität erarbeitet. Dazu haben die Projektpartnern AWI, die Firma Zordel und dem LAVES-IFF ein neues Fischtransportmodul entwickelt, welches eine Wasseraufbereitung beinhaltet und die Wasserqualität während des Transports für das Tierwohl unter Berücksichtigung der Lebensmittelsicherheit und -qualität optimiert. Das AWI und die Firma Zordel haben hierfür einen Prototyp mit integrierter Wasseraufbereitung, basierend auf einem Airlift- kombinierten Zeolithfiltersystem, entwickelt und konstruiert und in Transportsimulationen getestet. Das LAVES-IFF hat die Lebensmittelsicherheit und -qualität insbesondere in Bezug auf Veränderungen in der sensorischen, chemischen und mikrobiologischen Fleischqualität und -sicherheit begleitend untersucht. Diese Parameter waren zum einen für die Wirtschaftlichkeitsanalyse unerlässlich und zum anderen in enger Verbindung zum Tierwohl zu sehen, welches anhand von gängigen Stressparametern bereits am lebenden Tier durch das AWI bestimmt und beurteilt wurden. Die entwickelte und erprobte Wasseraufbereitung wurde abschließend in ein Fischtransport-LKW der Firma Zordel integriert und unter realen Bedingungen getestet. Ergenbisse: In Simulationsversuchen bei kommerziellen Transportdichten konnte gezeigt werden, dass der Airlift/Zeolithfilter sich deutlich positiv auf kritische Wasserparameter auswirkte. Der Anstieg des fischgiftigen Ammoniums im Haltungswasser konnte um bis zu 25 % gesenkt werden. Zudem konnte die Kohlendioxidkonzentration im Wasser auf einem konstant niedrigen Niveau von ca. 20 mg/L gehalten werden. Die erzielten Verbesserungen der Wasserqualität hatten auch einen positiven Einfluss auf das Tierwohl der transportierten Forellen. Es konnte eine signifikante Reduktion des Stresshormones Cortisol detektiert werden und auch giftiges Kohlendioxid im Blut der Tiere konnte deutlich reduziert werden. Die positiven Effekte der Simulationsversuche konnten bei Realtransporten bestätigt werden. Sowohl Wasser- als auch Tierwohlparameter zeigten deutlich bessere Werte als im Transporttank ohne Wasseraufbereitung. Auch unter erhöhten Forellen- Transportdichten konnten verbesserte Kohlendioxidkonzentrationen im Haltungswasser erzielt werden und die Stressbelastung der Forellen blieb niedrig. Die ermittelten Ergebnisse zur Lebensqualität und -sicherheit zeigten, dass das erweiterte Transportsystem auch Auswirkungen auf das Lebensmittel hat. Es ist zwar für den Verbraucher beim Verzehr der Filets nicht möglich, konventionell transportierte Regenbogenforellenfilets, die direkt nach der Schlachtung gewonnen wurden, von denjenigen zu unterscheiden, die mit dem erweiterten System transportiert worden sind, jedoch konnte hinsichtlich der mikrobiologischen Lebensmittelaspekte erkannt werden, dass es zu einem geringeren Qualitätsverlust bei Lagerung der Erzeugnisse kam. Verwertung: Die erzielten Ergebnisse im Projekt führten zu einer direkten Entwicklung eines kommerziellen Prototyps für den Fischtransport. Es konnte gezeigt werden, dass sich die im Labormaßstab ermittelten Ergebnisse auch auf einen kommerziellen Maßstab übertragen lassen. Die Firma Zordel konnte auf Basis der im Projekt entwickelten Ergebnisse ein Transportfahrzeug aufbauen, welches in der Lage ist eine deutliche Verbesserung der Wasserqualität während des Transportes sicher zu stellen. Das System wird inzwischen dauerhaft durch die Firma Zordel bei Fischtransportern eingesetzt. Die Projektergebnisse führten auch zur Entwicklung eines Schnellfiltersystems, welches zum Patent angemeldet wurde.

Description: Uneven growth of aquacultured shrimp leads to an increase in cannibalism, untargeted feeding and uneven product size. Size grading can prevent these effects. However, current sorting methods are highly invasive and cause high stress levels and flight responses. The animals can injure themselves and may even jump out of the tank. In this study, a size grading device was developed that allows the animals to sort themselves voluntarily according to size in the cultivation tank. For this purpose, innovative structures were developed that are specifically adapted to the body shape and behaviour of the animals. These structures are conceptualised to either encourage or discourage passing of the grading device. Results demonstrate strong grading effects (75 %) on the distribution of shrimps between different tank compartments and the ability to separate shrimps of different size voluntarily (up to 85%). Small animals can be separated from the cohort without stress or any personnel effort and uniform size distribution of the shrimps can be guaranteed. This voluntary grading system is expected to increase animal welfare and growth performance in shrimp farms while it reduces labour.

Description: Introduction Further development of recirculating aquaculture systems (RAS) towards zero-exchange depends mostly on the improvement of water treatment technologies. Ozone and UV radiation are leading technologies requiring high energy demand and educated staff able to manage the hurdles of their application. Moreover, there are some constrains for systems with poor mechanical filtration or where accumulation of particles higher than 50 µm significantly reduce the penetration potential of UV application. An alternative method commonly used in wastewater treatment to eliminate particulate aggregates is sonication. This method is based on cavitation effects which contribute to disrupt bacterial bioflocs and to break microbial cell walls leading to reduced viability. The present study aims to evaluate the disinfection capacity of a prototype created to treat process water in a RAS rearing aquaculture relevant freshwater and saltwater species with three sonication frequencies. The potential impact on the microbiome of the system in different compartments beside the reactor as well as bacterial viability was evaluated. Material and Methods An ultrasound prototype composed of 12 inducers connected to control devices was created in the frame of this project and adapted to a 5 m3 research RAS composed of three rearing tanks, a drum filter, 2 biofiltration units (nitrification denitrification), a sump and a protein skimmer with ozone disinfection. For the experiments the system was initially prepared for rearing European Seabass (Dicentrarchus labrax) and in a second experiment for rearing tilapia (Oreochromis niloticus). Process water coming from the sump was conducted into the prototype at a flow rate of 10 l/min and treated with 575 kHz, 862 kHz and 1142 kHz without further disinfection. For the saltwater experiments we tested 50% and 75% frequencies amplitude while only 75% amplitude was used for freshwater experiments. Each frequency was applied for 96 h and daily sampling was conducted to determine variations on microbial viability (BacLight Viability Kit) and bacterial community composition (FISH) with respect to reference samples collected before treatment. For FISH analysis (Fig. 1) generic FAM labelled DNA probes for Eubacteria (EUB) and Archaea (ARCH) as well as more specific probes for α-, β-, γ-, δ-Proteobacteria (ALF, BET, GAM, DELTA) and Actinobacteria (HGC) were included. When available, also non labelled competitor DNA probes in equimolar concentration as the respective labelled probe were used. All samples were counterstained with DAPI. Results and Discussion Marine RAS: The sterilizing effect was impacted by the amplitude used. Frequencies 575 kHz and 1142 kHz showed higher disinfection potential by 75% amplitude than 50%. The proportion of dead cells increased with the frequency. At 1142 kHz, a decrease in the total number of most of the selected bacterial groups was detected (Fig. 2) while the total numbers of bacteria at the end of application did not significantly change when using 575 kHz and 860 kHz. Sonication with all tested frequencies lead to changes in the bacterial community. Especially at 1142 kHz, a strong decrease in ALF, BET, GAM and ARC and an increase in DEL was observed (Table 1). This suggests a selective effect of US treatment on microbial community. Freshwater RAS: The sonication treatment of the system while rearing freshwater species did not show a defined impact with respect to changes in bacterial composition over time. At a frequency of 860 kHz, there was an increase in the number of counted bacteria over time (Fig. 3) while a slightly drop was observed by 575 and 1142 kHz. No marked changes in the composition of the bacterial community were detected for the latter frequencies. For all frequencies tested there was no conspicuous change in the percentage of dead cells.

Description: Aquacultural EngineeringVolume 83, November 2018, Pages 20-26

Description: Introduction Recirculation Aquaculture Systems (RAS) use water recycling as the base for an efficient production. Water reutilization demands cleaning techniques to remove accumulating compounds. These include mechanical filtration, biofiltration and a disinfection method. The most common disinfection methods used in RAS are UV and Ozone, both having pros and contras in terms of costs, risks, and application requirements. An alternative to these methods is hydrogen peroxide (H2O2), which, even been classified as a green oxidant, has not been commonly used and is hardly criticized due to acquisition, storage and secure manipulation issues. As H2O2 dissociates into non-toxic environmentally benign by-products including oxygen, its application offers potential savings in terms of oxygenation in RAS. Moreover, H2O2 is used to treat ectoparasitic illness with FDA approved H2O2-35% dosages between 50-1000 mg/L for 15-60 min. Minimum concentrations to which stress responses have been observed in salmonids range between 4-170 mg/L while the limits for biofilter function are around 5 mg/L [1-4]. Materials and methods In the present study, we perform serial experiments in a RAS rearing ~65 kg European seabass (Dicentrarchus labrax, weight ranging from 500-800g) to test the best application possibilities for H2O2 into a system, with concentrations between 2.4-15.8 mg/L/h. We tested two application positions: the bypass between the protein skimmer and the sump (with higher organic burden), and the flow to the rearing tanks (low organic load). We evaluated the impact on physicochemical parameters with focus on oxygen and nitrogen species concentration and the effect of the application on bacterial community of the different compartments (assessed via total bacterial counts in CFU/ml). Dosage was applied for 4 h on a daily basis and rates of decay of H2O2 on the system was assessed with Quantofix Peroxide test sticks (Sigma Aldrich, from 0-25 mg/L and 0-100 mg/L) until total removal. Ozone was switched off during dosage. Smart Digital S-DDA (Grundfos, Germany) dosage pumps were used for a controlled H2O2 application to the system (dosing capacity between 2.4 ml/h and 7.5 L/h). Stress levels of the reared fish was assessed using cortisol and glucose as blood markers. Results With the concentrations used, we accomplish a partial disinfection of the system without reaching levels affecting the bacterial flora of the biofiltration units or the health of the reared fish. We found a significant reduction of the bacterial load with each of the concentration tested. The best application position was the inlet to the protein skimmer, due to the lowest impact to the bacterial flora of the filter and the reared fish. An economically relevant increase in oxygen level of the system as well as the highest disinfection levels were achieved with 15.8 mg/L/h. In this assay, an artificial oxygen depletion was simulated before applying H2O2 to the system, and this was recovered within the first 40 min, even during a feeding period, which normally reduces the oxygen level in the water column. After application, the rates of decay varied from 30 min to 1 h, time after which, no H2O2 was detected in the system. No significant negative effects were found on fish stress markers even when cortisol (Ref: 59.8±49.5 vs. Treat:62.2±43.5) and glucose (Ref: 131.0±34.9 vs. Treat: 155.1±45.3) levels tended to increase during the experiments using increasing H2O2 doses. These markers showed a high variability. During application, the number of fish showing conspicuous low cortisol levels increased. Discussion and conclusion Organic burden in the system, fish stocking density, feeding frequency and biofilter performance were all factors influencing the required H2O2 dosage and its rate of decay in accordance to what has been published [2, 5, 6]. In the present study, we found a relatively rapid decay of H2O2 remnants, supported by the organic load typically present in a RAS rearing at commercial or semi-commercial scales. We recommend to apply H2O2 in positions of the system with high organic burden to avoid affecting biofilter function or promoting nitrite accumulation as previously published [5]. Despite previous results showing negative stress responses of D. labrax to H2O2 application [7], we did not found critical changes on cortisol or glucose related to the treatment. These authors used smaller fish (weight 120-200 g) and doses of 50 ppm/h, which are higher than in the present study. The stress in D. labrax is genetically driven and highly dependent on size/age with individuals having consistent high (439.2 ± 31.1 µg/dl ) or low (247 ± 85.1 µg/dl) cortisol concentrations and, as well as glucose, there is a circadian pattern for these parameters within this species [8, 9]. Glucose levels between 100-150 mg/dl have been reported in the literature for D. labrax [10]. With appropriate knowledge of system performance and microbiological background, H2O2 can be a positive complement to the disinfection spectrum of a RAS. It can be used alternating with common methods to avoid artificial selection of specific microbial groups and can have a positive impact in cases in which parasitic illness are present. Thus, as a disinfection method with a plus for its oxygenation influence, H2O2 can enrich the disinfection portfolio of aquaculture facilities.