The natural environment of sturgeon is the Northern hemisphere where they live in rivers and the sea. Many sturgeon are anadromous fish, viz. they swim for spawning from the sea up into the rivers. The main volume of fish can be found in the Caspian Sea as well as in the Black Sea.
The reproduction capacity of sturgeon need a relatively long time and starts at different age levels depending on the species. Also the sum of the day temperatures in their particular environment plays an important role. Sturgeon of similar species will have an earlier sexual maturity in warmer waters. A female of the Siberian sturgeon (A.baerii) bred in North German climate needs 9-11 years to mature, a Beluga (Huso huso) even 25-30 years. In their natural biosphere sturgeon are climbing up the rivers for spawning and leave their eggs on sand/gravel ground. Dams and other regulatory measures are forming tremendous obstacles for the fish, which in some places they cannot overcome.
The Soviets started artificial reproduction of sturgeon already in the 1950s and released the fingerlings into the rivers for sustainable management of the fisheries. After the fall of the Soviet Union and the consequent unregulated fishing the stock of sturgeon decreased drastically in the 1990s. This development was worsened by the black market trade and the fact that stocks were not replenished by artificially reproduced fish.
SPECIES OF STURGEON AND THEIR IMPORTANCE FOR THE CAVIAR PRODUCTION
Sturgeon have existed on our planet since more than 250 million years, thus being one of the oldest of fish on the earth. The family of sturgeon (Acipenserformes) consists of 27 species which are divided into two sub species: the actual sturgeon (Acipenseridae) with 25 species and 2 species of paddlefish sturgeon. Only a few sturgeon species are used for the production of caviar. Meanwhile there are some trials made to pair particular species of sturgeon in the hope to achieve an acceptable, maybe even improved end product.
PROTECTION OF SPECIES
On the 1st of April 1998 sturgeon were put on the list of the Washington Convention and trade with sturgeon and caviar was possible only under the rules and regulations of CITES (Convention of International Trade in Endangered Species of Wild Fauna and Flora). From then on sturgeon fishing was regulated by quota and the trade with caviar was controlled and regulated by particular marking and documentation rules. In spite of these measures the decrease of sturgeon stocks could not be sustainably stopped. Since 2009 therefore no fishing quota are granted anymore. Consequently since that time no caviar from wild sturgeon may be produced anymore but only the trade with caviar from aquaculture is permitted.
STURGEON IN AQUACULTURE & POND FISHERY
STURGEON IN AQUACULTURE
Since the start of the 1990’s sturgeon are bred and kept in aqua culture. At first it was mainly the Siberian sturgeon (A.baerii), but fairly quickly followed by the other species.
Nowadays aquaculture industry does not only breed and keep a respectable number of sturgeon species but has also developed into a substantial source of information in the questions of means of replenishing stocks and the necessary reproduction measures. The peculiarity of breeding sturgeon is the long time it takes. No other fish in aquaculture must be kept for such a long time before it can be processed.
Possible breeding targets are consequently time consuming and difficult to reach. Growth of the fish and development of the ovary is very dependant on the water temperature. In warm water the fish are growing and maturing considerably faster.
Therefore the sturgeon are often kept in warm water circulation systems. Here, however, the fish (and the eggs) are collecting substances that create an off-taste of the caviar. Moreover the single grain often does not have a tough enough skin so that the caviar turns out too soft.
Therefore, at the start of their aquaculture activities, DIECKMANN & HANSEN rather invested in the spring fed pond fishery. Change of temperature and light during the different seasons of the year as well as the partly natural nourishment and last but not least more freedom of movement allows the single caviar grain to develop a firmer shell. Before the fish are finally processed they are set into sandy lagoons, with the cooler waters of the spring running over and through. Any strange taste is avoided that way.