Zander fry from Hessenaue

Zander is considered to be one of the most promising fish species for production in closed recirculating aquaculture systems. One problem, however, is that there are not enough fry available that have been adapted to dry feed. This could change now, however, because in May 2013 Fischmaster IP Services GmbH opened an ultramodern facility for the reproduction and farming of zander fry. The investment was made without any subsidies.

Viewed from the outside you wouldn’t think that on the two hectare site in Hessenaue near Trebur, within the triangle between Frankfurt, Darmstadt and Mainz, you would find one of the most modern recirculating systems in Germany. No big oxygen tanks, no insulated functional buildings, not even any transport containers for fish are to be seen. The whole complex with its16 buildings – an air force homestead that was built in 1938 and has since then experienced a variety of different uses over the course of the years – is a listed building and site and thus under protection. This places particular architectural and historical obligations on Eric Nürnberger, the founder and manager of Fischmaster. He is not permitted to insulate the outer facades and when any of the much needed restoration work is carried out it has to be in exact accordance with fixed stipulations – from the kind of wood to the colour of the windows. On top of that, the site is also a conversion area because the homestead was mainly used for military purposes during its varied history: as part of a military airfield, as an army storage depot, and as a police training ground. Before he could start building at all Eric Nürnberger had to have about 60 holes drilled into the ground throughout the whole site and even beneath the buildings to enable investigations that were necessary to attain the required soil, water and pollution reports. There were no water or electricity network plans, all the cables and pipes were old or no longer dependable. Whatever you touched, seemed quite dilapidated, Nürnberger remembers. He had kilometres of cable and 45 power distribution boxes installed. It took about six months just to get things tidied up and make preparations for the building process. Anybody who does all of that voluntarily must be very convinced of, or even obsessed with, the idea that this would be an excellent place for aquaculture.

Eric Nürnberger. For the delivery of the zander fry to fish farmers and angling clubs there is a suitably equipped trailer with transport containers available.

Eric Nürnberger is a passionate hobby angler and the idea for the aquaculture facility had taken seed at a course for fisheries supervisors in which he had taken part, when someone talked about aquaculture and indoor recirculating technology. He began to do his own research on the topic, try things out, and for many years ran his own small experimental plant in a garage. And he contacted a supplier of aquaculture technology. It is from that time that his connection with the fish farming expert Peter Schumacher stems. Schumacher has in the meantime set up his own business as a consultant for aquaculture planning, projects and ventures. After thorough examination of the market situation Eric Nürnberger gave up his original plan to build a farming facility for zander and decided instead to invest in fry production. At first he wanted to set up the recirculating system in Trebur’s Astheim industrial park where he already has two IT companies. Then it was to be built in a green field environment and he had even already purchased five hectares of agricultural land to this purpose. But although the local authority showed a lot of interest, the plans were initially unsuccessful because for one thing Nürnberger failed to gain the required operating licences and for another there were infrastructure problems. When in November 2011 the old homestead was to be sold via a public auction he succeeded in buying it and his project soon began to take concrete shape. Construction work began already six months later after he had worked out the technical design of the plant together with the project team behind Peter Schumacher.


Room-in-room construction creates space within the facility

On account of the constructional limitations due to the preservation order Peter Schumacher had to look for alternative solutions when planning the recirculating system. The lower floor of the building was completely gutted to create a total area of slightly more than 750 square metres. That was enough space to install four new insulated rooms for the facility. These rooms stand freely within the building like dolls in the belly of a Russian Matrjoschka. “Room in room” is what Schumacher calls this construction type which is rather complex but offers several advantages. Cables and pipelines do not have to be sunk into the ground (an expensive process), for example, but can be positioned much more cheaply to the side of the installation. There they are more easily accessible for inspection and maintenance at any time. Apart from that, the layer of air between the inner and outer structural shells constitutes effective insulation which facilitates precise control of room temperature and prevents the rooms from becoming flowstone caves.

The four rooms within the house now contain five recirculating modules with a good two dozen tanks of various sizes which were specially produced in Turkey. Added to these are several 700 litre aquariums in which the eggs are hatched and the larvae are kept and fed after hatching. Water treatment comprises not only a drum filter but also an organic filter which is divided into fixed bed and moving bed zones. Above the moving bed is a CO2 extractor that is fitted with a heat exchanger for recovery of energy. At the end of the process the cleaned water is sterilised with UV light and enriched with oxygen from an oxygen generator in an adjacent technology room. All the systems are arranged in a logical order and are easily accessible. There are broad aisles and open areas in all the rooms to offer the employees good working conditions.

To encourage the parent fishes to maturity outside the normal spawning period the system manipulates environmental parameters to give the appearance of different seasons.


Self-sufficient energy supply and manipulation of maturity

The farm is geared to sustainability, low consumption of resources and minimisation of energy consumption. It is mainly supplied with solar, wind and increasingly geothermal energy, too. Where it makes sense and pays off heat energy is recovered and recycled. Part of the electricity required to operate the plant comes from a photovoltaic system which delivers 95 kW at peak times. The plant is also heated at night by means of an intelligent cascade of high-temperature heat pumps. To achieve this, water is gradually heated to a temperature of 80°C and then stored in two buffer tanks each with a capacity of three cubic metres. In the near future Eric Nürnberger would even like to increase the share of renewable sources in his energy supply. “At present we produce about 70 per cent of the required electricity ourselves. But the aim is to produce 100%, which would mean full self-sufficiency.” He intends to install further solar panels on the homestead site. That would mean he would have enough electricity available to produce hydrogen by means of electrolysis and this could be used at any time in fuel cells for heat and electricity production. “We are only planning to become fully self-sufficient, however, and not to feed power into the public network.”

Water treatment includes a drum- and an organic filter with CO2 extraction, a UV sterilisation plant and oxygen enrichment.

The most important company goal is, of course, the production of zander fry which should as far as possible be year-round. In order to bring the parent fish to maturity outside the regular spawning time the environment parameters are manipulated to give the appearance of changing seasons. To achieve this an elaborate electronic control system was developed which mimics the seasonal changes through different light and temperature parameters. After a brief “summer” with more than 16 hours light and 20°C follows “winter” with shorter light phases and lower water temperatures. The coming months will show whether that alone will be sufficient to stimulate the zanders’ maturity or whether other environmental factors will have to be modified, too. To begin with, the potential parent fishes have been divided into four groups for maturing so that – if everything works as intended – a group of fishes will spawn every three months. The longer-term aim is to achieve a monthly spawning rhythm. The capacity of the plant would be sufficient to produce two million zander fry per year.


Weekly sorting prevents cannibalism

With nearly 300 fishes Fischmaster has a substantial parent fish stock. Each of the four seasonal spawning groups comprises a good 70 two-year-old zander that grew in a recirculating system from NDF (Norddeutsche Fischhandelsgesellschaft). They will all be spawning for the first time. Coconut mats serve as spawning nests and once the eggs have been laid the spawn is transferred to the aquariums. After they have eaten the yolk sac the larvae first feed on Artemia nauplii and then at an age of two weeks weaning begins so that they switch to dry feed. About 12 weeks after hatching, the young zander weigh between 10 and 20 grams and can be sold to fish farmers and fishing clubs. In their early life phase not only the transition to dry feed was difficult, said Michael Jüling who is responsible for the zander fry and has a Masters degree in aquaculture, but also the strong divergence in growth rates among the young zander stock. To prevent cannibalism by the fast growers the stock had to be size-sorted practically every week.

Demand for zander fry for stocking purposes is already high and likely to rise further in the future. Since word has spread among sports fishermen that young zander are produced in Hessenaue, fishing clubs have been asking nearly every day for the popular angling fish, particularly since Fischmaster does not only offer ten and twenty gram fry but can also supply zander weighing about one kilogram. These are produced by NDF with whom Fischmaster in the meantime cooperates closely. Fischmaster supplies NDF with fry and in return is given larger fishes that are then sold in the region. This is an additional business section that demands very special logistical requirements, however. During the coming months Eric Nürnberger is going to set up a holding facility with three big tanks in an adjacent building.

Up to now Artemia were hatched in this small system but a new system with considerably more capacity is currently under construction in an adjacent room.


Aquaculture training centre conceivable

It’s not easy to foresee when the construction activity on the homestead site will reach its end since all 16 buildings are being gradually refurbished. The generously sized sanitary facilities that were once built for military use have already been renewed and in the other buildings modernisation of the interiors is nearing completion. The renovation of the timberwork gables and exterior facades is proving to be particularly complicated since specialists are needed for this task. Old larch shingles have to be carefully removed one by one, thoroughly cleaned and then re-inserted. Because it is today no longer possible to get replacements for damaged shingles in Germany Nürnberger has already had new ones produced in Poland, hand-worked to the original. When the entrepreneur had the sewage system on the site renewed a rumour immediately took hold of the neighbourhood that the recirculating system would probably emit so much water that it would even be necessary to enlarge the sewage system of the municipality. But Eric Nürnberger was able to calm these fears which were completely unfounded, because his plant needed less water than a normal family home.

There might even soon be a training centre for aquaculture or a fry competence centre on the Hessenaue site that would offer aquaculture courses and training. Eric Nürnberger believes there is a lot of interest in such offers because he is getting a growing number of enquiries about lectures and guided tours through the facility. There would certainly be enough space for such courses on the site, the rooms would just have to be fitted and equipped accordingly.



Fischmaster IP-Services GmbH
Niersteiner Straße 38
65468 Trebur

Telefon: + 49 (0) 6147 913 0
Telefax: + 49 (0) 6147 913 200

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