POLAND
The Dgał Experimental Stocking Centre grows fish for research, restocking, and revenue
A focus on sturgeon and other high-value species The Dgał Experimental Stocking Centre is a unit of the Inland Fisheries Institute, which carries out experiments to improve the breeding of fish species with a particular focus on sturgeon and other high-value species for both restocking and sale.
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turgeons are an anadromous species, which means they migrate from the sea to freshwater for spawning. In Poland, they have been recorded travelling as far as 700 km for this purpose. In a recirculation system, the spawning of sturgeon takes place in January and February and takes about two months. It is more complicated than with other species, but the Dgał Experimental Stocking Centre has been doing it successfully for 12 years.
The conditions in the basins imitate the fish's natural environment. During winter, water temperatures are decreased and then gradually raised and lights are turned on to signal spring. The fish do not produce eggs every year, so several stocks of each species have to be maintained according to the number of years between spawning (two years for Siberian sturgeon, four years for Russian, and at least four years for Atlantic sturgeon). Atlantic sturgeon is a delicate species and is bred for restocking in the Baltic Sea region, but plans are being made to produce the fish for sale. Atlantic sturgeon matures between 13 and 14 years of age when females reach a weight of ca. 50 kg. In the wild, maturity would not occur before they reached 18 to 20. Being sensitive, they react to anything: movement, sound, and lights being 30
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turned on and off. Because of this, losses of Atlantic sturgeon are more frequent and still occur after they reach 1 kg, whereas other sturgeon species experience practically no losses. The species can reach sixty years in age and grow to almost 5 m, with weights exceeding 300 kg. Today, natural sustainable populations are maintained only in the US and Canada. In Europe, they are almost entirely extinct, so stock restocking is highly prioritised. Studies have revealed that the sturgeon population in the Baltic Sea belongs to the Canadian subspecies rather than the European variant, as previously thought. Research indicates that this species migrated to the Baltic approximately 1,300 years ago and subsequently displaced the native species. Most experiments are carried out on the Siberian sturgeon, because it is the easiest to grow and reaches sexual maturity at the age of only 8, making it the species of sturgeon most commonly bred in captivity. Research focuses on obtaining the female stocks by, for instance, hormonal reversal of sexes. But the coding system for sexes is different in sturgeon than in other species. Currently, it is not possible to genetically distinguish males from females, and only when they reach a size of
Fish for restocking are tagged to allow them to be traced.
ca. 1,5 kg can the sexes be identified using ultrasonic scanning; but this is labour intensive and therefore done only for restocking or in connection with the production of caviar.
source breeding materials from our hatchery and sell them to Russia. We sell sturgeon weighing 1 to 2 kg to Russia, and thus Polish sturgeon is the origin of Russian caviar. At least some of it”.
Polish sturgeon behind Russian caviar
A fish for the future?
Russian sturgeon is excellent for caviar, so-called black gold, because their eggs are big and very black and this makes them more sought after, although they mature later (ca. 12 years of age). They grow without much effort to 200 kg and 3,5 m. Two companies in Poland breed sturgeon for caviar. According to Mirosław Szczepkowski of the Stanisław Sakowicz Inland Fisheries Institute, “We have many customers in Lithuania who
Pike-perch is bred from the institute's own broodstock. “Everyone wants to breed this species, but unfortunately, it is very difficult”, says Miroslaw Szczepkowki. “Especially at the initial stages, growing them from eggs to 1 to 2 g fish and getting them to eat feed. There are farms in Denmark and Poland that specialise in growing them, but in Poland, we are the only ones who grow them from scratch”. The species is only bred for restocking but there is a huge demand for this fish once they www.eurofishmagazine.com
05/12/13 1:01 PM