Introduction

WU-AFI (Aquaculture and Fisheries) belongs the Department of Animal Sciences of WU. It lectures in the MSc Aquaculture and Fisheries and organizes intensive courses/workshops on recirculation aquaculture system (RAS) technology. WU-AFI has 40 years record of research on the interaction and modulation of fish and rearing environment in intensive farming systems, such as RAS. It developed expertise in: (1) growth, nutrient and energy metabolism using metabolic chambers and (2) the engineering and operation of RAS systems (since the 80’s) and is now worldwide recognized as one of the leading experts in that area.

Aquaculture scientists visiting this facility can benefit from Wageningen Aquaculture Research Facility, a 1800m2 aquatic indoor recirculation systems-based research facility (approximately 65 RAS and 560 holding tanks). The facility contains: (a) the Metabolic Research Unit, which offers a research environment for studies on nutrient and energy balances and metabolism in fish (both over a production cycle and for within-day variations, and (b) the Recirculation Facility consisting of sets of identical lab scale and pilot scale RAS to replicate treatments on system level. Both installations are stand-alone research installations which are each located in a separate room offering a research environment on organism level (WU-MRU) and production system level (WU-RAS). Marine and freshwater pilot scale RAS can be extended with several water treatment units (e.g. a single sludge denitrification reactor or a Geotube®system).

WU carries out research in Fish Nutrition, Fish Production Systems and Fish Health and Immunology. Animal experiments in Fish Nutrition and Fish Production Systems are conducted in fresh water or salt water species. For research on Fish Health and Immunology genetically well-defined carp and zebra fish inbred lines are used which can be combined with the use of a standardised blood parasite (Trypanosome) infection model. The research on Fish Nutrition and Fish Health and Immunology is performed in the metabolic research chambers (WU-MRU).

Expected output/deliverables for users: Publications describing the effect of animal, nutritional and environmental factors on responses of fish (output WU-MRU) and on system responses (output WU-RAS).

Fish responses are: e.g. feed efficiency, feeding behaviour (latency and feeding time), digestibility, immunological, heat production (energy and nitrogen balance), and behaviour are among the measurements performed. In addition, these measurements may be combined with blood parameters and anything you can measure at slaughter. System responses are: e.g. water quality, water treatment performance and environmental performance (system waste discharge).

WU-MRU (The metabolic Research Unit)

Infrastructure: WU-MRU (The metabolic Research Unit)

Location: Wageningen, THE NETHERLANDS

Web site address: www.wur.nl/en/Research-Results/Chair-groups/Animal-Sciences/Aquaculture-and-Fisheries.htm

Contact: Roel Maas (roel.maas@wur.nl)

Facilities

The WU-MRU is used to study how nutritional, animal and environmental factors affect responses of fish (organism level, WU-MRU). The WU-MRU consists of twelve metabolic chambers (200L each) linked to a recirculation system with a total water volume of ± 7m3. The recirculation system is equipped with an independent water quality (pH, salinity, temperature) measurement and control system. The metabolic unit is placed in a room with adjustable photoperiod. It has on-line measurement of actual and cumulative water flow per metabolic chamber, oxygen, temperature, pH, conductivity (µS), salinity, CO2 production/consumption, TAN, urea, NO2-N, NO3-N, dissolved protein, and PO4-P in the rearing water, using an auto-analyzer (Type San autoanalyzer adapted with flow through cuvettes, Skalar, Breda, The Netherlands). The twelve metabolic chambers can be equipped with a mobile feeding registration system. Mobile faecal collection units (12 sedimentation funnels) can be used to study the digestibility of feed nutrients. Mobile webcams (N=16) and imaging analysis software are available to record and analyse behavioural data. The metabolic research unit is equipped with a data acquisition system in which all data can be stored and made available in excel spreadsheets for later analysis. The unit can be connected to two identical RAS differing in water quality (pH, salinity, water exchange rate, nitrate level) to study the effects of these factors on the response of fish.

The metabolic research unit is commonly used for studies on nutrient and energy balance studies in fish (both over a production cycle and for within-day variations) and for studies on the adaptive physiology of fish. The WU-MRU: (1) can be supplied with four water flows differing in oxygen or carbon dioxide concentration each flow supplying 3 metabolic chambers; (2) can be used to determine O2 consumption and CO2 production by fish, (3) has a high accuracy and stability for the online water flow measurement across the metabolism chambers, (4) is equipped with a webcam per chamber for behavioural studies, (5) enables researchers to perform experiments for both freshwater and marine organisms (salinity can be varied from 0 to 35ppt) and for cool and warm water fish (water temperature can be controlled between 15 and 30 °C), (6) allows the determination of within days variation in O2-consumption (from water), CO2-production (in water), TAN, urea, orthophosphate, temperature and pH trough online water quality measurement.

Services currently offered by the infrastructure

The metabolic research unit offers a research environment for studies on nutrient and energy balances and metabolism in fish (both over a production cycle and for within-day variations). The research questions in the metabolic research unit relate to how animal factors (genetics, phenotypic differences, and health status), nutritional factors and environmental factors (temperature, oxygen concentration, carbon dioxide concentration, stocking density, sex ratio and housing conditions) affect responses of animals.

However, over the past 5 years, research has focused on adaptive physiological responses of fish to various husbandry conditions, such as the changes in feed intake behaviour and nutrient utilisation when ambient oxygen conditions are pre-set at different levels (tilapia) or carbon dioxide levels are pre-set at different levels (seabass). Studies were combined with changes in feed composition (substitution of animal by plant proteins, and different levels of non-starch polysaccharides, affecting the viscosity of the chyme and other intestinal ecological parameters), chronic (density; light conditions) and acute (netting) stress conditions, etcetera. Measured responses in the metabolic research unit strongly depend on the research questions involved, but generally, feed efficiency, feeding behaviour (latency and feeding time), digestibility, heat production and behaviour are among the measurements performed. In addition, these measurements may be combined with blood parameters and anything you can measure at slaughter.

Lab analysis of immune responses such as real-time PCR analysis of expressed genes, ELISA-based analysis of antibody or cytokine production, flow cytometric analysis of changes in leukocyte cell populations and analysis of proximate composition of fish, feed, faeces and sludge are routinely performed. An auto analyser is available for online measurements of TAN, urea, NO2-N, NO3-N, dissolved protein, CO2 and PO4-P in the rearing water. The WU-MRU is equipped with remote access sensors measuring oxygen, pH, temperature, conductivity and water flow rate. Sixteen (16) remote access cameras are available for recording of fish behaviour.

Visiting scientists and PhD’s have carried out research in the metabolic research unit. Studies in the WUMRU were partly conducted through EU funded research (for example: AquaExcel-FP7 and the WEALTH project (SSP8-CT-2003-501984) investigating the metabolic effects of rearing European seabass in extreme high densities, and at high CO2, low O2 levels in RAS).

Modality of access

A project will typically last 3 months, whereby the users spend part of the 3 months’ time (the maximum stay at the infrastructure is 90 days) for preparation of the final work protocol, discussion with the local WU scientists and supporting staff, and discussion of the results. The effective use of the infrastructure for experimentation during each project will be 8 weeks. Within AQUAEXCEL3.0, the WU-MRU infrastructure will receive four projects of 3 months each during the project duration, thus 4*8=32 weeks of infrastructure use. When a proposal is selected, a host-supervisor will be identified and allocated from the senior staff of WU. The visiting user group is expected to discuss details of the proposed research with this senior staff member who acts as an immediate local partner for the proposed research. The study will be further executed as a joint collaborative research project between the Aquaculture and Fisheries group (AFI) of Wageningen University and the project user group. This guarantees that the study is administratively registered as a Wageningen University Task, which facilitates the further administrative implementation.

The host unit (WU) will start all logistic and administrative procedures and supports the execution of the work by providing supporting staff (lab technicians, administrative support, fish care taking staff etc.) and scientific embedding and backing. The visiting scientists are expected to stay at least 8 weeks at WU and execute part of the experiment themselves: four weeks at the start of the experiment and four weeks at the end of the experiment (to be discussed with the host supervisor). In the meantime the practical work will be done by the infrastructure personnel.

The Aquaculture and Fisheries Group of WU will assist in the outline of the work protocol, submit the application for approval of the Ethical committee, and provide scientific backup on methods and results interpretation and act as co-author for eventual publication of the results.

WU technicians will support the proper execution of the experiments, keep track of the (mandatory) welfare logbook, purchase of fingerlings and feeds required, and act as liaison to the staff of the Aquatic Research facility (CARUS-ARF). Staff of the research facility will provide support in feeding the animals and preparing the infrastructure before/after its use in the project.

The visiting scientist will receive a workplace, including a WUR internet account for the duration of their stay, receive support in finding living accommodation and be registered as visiting scientist. The latter enables the formal support of all WU administration, e.g., finances, book-keeping, secretarial support etcetera. The e-infrastructure developed for the WU-MRU in FP7-AQUAEXCEL offers the visiting scientists through remote access (graphical presentation and downloading of (actual) sensor data time series and live video per metabolic chamber) to follow part of the experiment at home or allows colleague scientists at home to follow the experiments and discuss the experimental conditions through (Skype/Teams) video conferencing with their colleague and/or scientists/technicians in Wageningen.

The support offered is a standard support given to visiting scientists and PhD’s by WU.

Unit of access

The unit of access is defined as one week access to 12 metabolic chambers.