A demanding sh to breed and rear

Pike-perch is a high-value freshwater sh species found in lakes and rivers in Northern and Central Europe among other regions. The sh has also long been grown in polyculture with carps in the large earthen aquaculture ponds typical of Central and Eastern Europe. More recently, sh farmers in several European countries have started growing the species in recirculation systems where the water used to grow the sh is cleaned and reused. This technology is expensive to buy, install, and operate, but the high price the sh commands makes it worthwhile.

An agricultural engineer at Almásfüzit village in Komárom-Esztergom county, north-west Hungary, István Vida recognized an opportunity amidst the industrialization of this area of fertile land and gravel deposits. Mr Vida saw the bed of the gravel mine, continuously replenished by water from the Danube, become a haven for various sh species: bream, carp, perch, and pike-perch.

Experience growing several species

Ten years ago, Mr Vida established Fodina Fish Ltd.—the farm where originally only sterlet was hatched and grown. At a later stage, new species were added to the range: Russian sturgeon, beluga, and striped bass. Pike-perch was another species that attracted his attention: high demand on the European market and scarce supply were good preconditions to add this sh to the farm’s range.

In 2022 Fodina started rearing larvae and on-growing pike-perch in the farm’s recirculation facilities. e larvae are placed in cylindrical tanks with conical bottoms. Here an upwelling ow is supplied until the larvae develop swim bladders, which nishes about three weeks after hatch. Sprayers keep the water surface within the tanks clean to enable proper swim bladder in ation. Until the swim bladders are developed, sh are given live diets comprising highly enriched Artemia. e Artemia is enriched to ensure the quality of the larvae which in turn secures the quality of the nal product. e enrichment process comprises keeping the Artemia in well oxygenated water, to which commercial products rich in fatty acids have been added, for 12 to 24 hours. When the swim bladder is in ated and sh start developing stomachs, both the diet and the ow change. e sh are weaned o Artemia and switched to articial feed, and the ow of water within the tank becomes circular which, although more challenging for the sh, enables much better hygiene and much lower microbial density. e conical base is useful for cleaning the

Dr Uros Ljubobratovic, Hungarian University of Agriculture and Life Sciences (MATE-HAKI) and a consultant for Fodina Fish; a company employee; Istvan Vida, owner and manager of Fodina Fish; and Dr Beatrix Beres Szabone, Ministry of Agriculture tanks as the sludge can be easily ushed out by a single person. Once the juveniles reach a certain size, usually around 200-300 milligrams, they are transported to another unit with rectangular tanks, where they are placed in.

Using light technology to optimise growth

Istvan Vida together with Uros Ljubobratovic, a researcher at the Research Centre for Fisheries and

Aquaculture of the Hungarian University of Agriculture and Life Sciences (MATE-HAKI), who also works as a consultant for Fodina Fish, is experimenting with articial lighting in the early stages of sh development. With the evolution of technology, arti cial lighting has become a crucial component of modern aquaculture practices, especially in indoor and controlled environment systems. Light in uences sh growth, reproduction, behaviour, and overall health.

Mr Vida uses two types of light in his indoor facility: in the early development of larvae, in-tank illumination with yellow light is used until the sh start developing retina when the light intensity is gradually reduced. When sh are moved to rectangular tanks, red light is used, and sh react well to it, since they are already adjusted to darker conditions and are capable of grazing in the dark. Above-tank red lighting though still allows the farmer enough light to monitor the sh. is is important because pikeperch in their early life stages are highly cannibalistic and therefore have to be graded often to ensure that sh of di erent sizes are not together in the same tank as this tends to foster aggression and cannibalism. Mr Vida is hopeful that as successive generations are bred this tendency will attenuate.

Feed management is facilitated with floating diets

After weaning the sh are introduced to oating diets. is acclimatisation is very important, says Dr Ljubobratovic, because the management of the feed is very di cult without oating diets in the given grow-out conditions. Once they are accustomed to the oating feed they are moved to another system of tanks where they grow to 20-50 g. e oating pellets are better, Dr Ljubobratovic nds, at reducing the variation in the sh size which is an important market consideration. ey are then transported to an indoor facility supplied with lake water which has a total capacity of three hundred cubic metres divided between twelve equal concrete tanks where rst year growing-out takes place. Generally, in extensive and semi-intensive facilities pike-perch commonly swim with other sh—carps, bream, and other species; at Fodina’s intensive facilities pike-perch is accompanied by sterlet. I call sterlet the shepherd of the pike-perch, says Dr Ljubobratovic, as it tends to prefer the sides and the bottom keeping the pike-perch in the middle. e nal grow-out to commercial size in second growing season takes place in outdoor concrete tanks of volumes 100-300 cubic metres per tank.

Growing sh in an outdoor facility has obvious advantages: the esh is a lot tastier compared to the sh coming from indoor units. e sh does not need purging which normally takes in RAS from eight days to two weeks, before the sh will be accepted by the market. e welfare of such sh is indeed higher, and their immune system is a lot stronger. Outdoor breeding is also bene cial for delivering the sh to the angling and restocking markets, as neither of these channels is quite satis ed with the sh they get from indoor recirculation facilities.

Mr Vida’s idea was not to maintain a broodstock and yet do the reproduction. “Virgins”, female sh ovulating for the rst time are used for this purpose. From the reproductive point of view, pikeperch are a very strong species—a female has up to 200,000 eggs per kg of body weight. To run a facility like Fodina Fish, one needs to start from half a million eggs—so two females would be enough, but the virgins have low quality eggs with poor survival rate, therefore more virgins are needed. is year the company selected the best sh to be reproduced and are currently working with 20-30 sh, and for the next year 50 or even more pairs are planned. e sh are selected for their appearance, shape, robustness, and for the growth rate.

Water is thermally conditioned for use in reproduction, larviculture, and juvenile nursing

Groundwater is used for RAS Fodina’s units—indoor larvae rearing and juvenile nursing and pre-growing. Its initial temperature is around 12°C, and the temperatures in the units vary between 4 and 29 degrees centigrade. Larvae grow at temperatures from 16°C when they are larvae up to 25°C when they are ready to be moved to the next unit. e juveniles are nursed at 20-22°C, as it is better for bone development, and because temperatures higher than that may promote cannibalism. At the outdoor facility during cold months the water temperature is around 4°C. So, depending on the destination the incoming water is either heated up or cooled down to provide the optimal conditions.

One of the novelties of Mr Vida’s approach is to send the wastewater to the walled-o section of a large pond to allow the sludge to settle. Some 70 percent of the sludge is pumped out to be used as agricultural fertiliser while the rest sinks to the bottom. e water from the settling pond is slowly mixed with that of the larger pond and then pumped back into the cultivation system. is arrangement combines recirculation with the use of existing infrastructure and is among the factors contributing to the high quality of the nal product. According to Mr Vida getting certi ed to an international standard would not call for any major changes in the way of production. An organic certi cation would call for the use of organically certi ed feed, of course, but it would be relatively easy to comply with maximum density requirements and with stipulations on the use of medicines. e sh is already being sold abroad but buyers are limited because of the modest

Fodina Fish KFT

Varosmajor u. 30 2900 Komarom Hungary

Tel.: +36 30 436 6637 fodina@tvn.hu https://www.fodina sh.hu/en/ fodina- sh-en/ volumes. Once we increase the production so that we can o er more than the current 20 tonnes or so I expect greater interest from foreign buyers, he says.

Aleksandra Petersen, Euro sh, aleksandra@euro sh.dk

Chief Executive Of cer: Istvan Vida

Scienti c collaborator: Dr Uros Ljubobratovic

Activity: Breeding of pike-perch

Market size: 0.8-1.2 kg

Volume: 20 tonnes/year

Markets: Hungary, Germany

Employees: 2