This paper presents an update on the global sturgeon and caviar production until 2017, attempting to continue previous efforts on summarizing the global trends in these markets. For the current update, an expanded data base was derived from questionnaires sent to 86 regional contacts in 46 countries, mostly farmers or scientists, and personal interviews. A total of 2,329 commercial sturgeon farms were recorded by 2017 globally, which represented an increase by 7% compared to 2016.Of these farms 54% were located in China, followed by Russia (24%), the Middle East (8%), the Far East (7%) and Europe (6%). Among the rearing technologies flow-through (FT) systems (36%) were most common, followed by recirculation aquaculture systems (RAS) (21%), cages (18%), mix FT/RAS (11%), and ponds (6%). In total the aquaculture sturgeon biomass production peaked at about 129,608 t in the year 2015, with a decline to 119,979 t in 2016, and to 102,327 t in 2017. China contributed about 79,638 t to the overall production in 2017, followed by Russia (6,800 t), Armenia (6,000 t), Iran (2,514 t), and 52 other countries with less than 1,000 t each.This production exceeded the fishery harvest during the 1970-1980s by more than four times. Of the 25 species of Acipenseridae, 13 pure species and four hybrids were farmed for meat with Acipenser baerii dominating production in 2016 with a share of 39.5%, followed by the two hybrids, Huso dauricus × Acipenser schrenckii and A. baerii × A. schrenckii (35.6%), as well as A. schrenckii (10.2%). Global caviar production increased during the last years and the production for the year 2017 amounted to approximately 364 t. China contributed more than 100 t to the overall production in 2017, followed by Russia (49 t), Italy (43 t), France (37 t) and diverse other countries. The species composition in caviar production in 2016 was dominated by A. baerii (31% of the total volume), followed by Acipenser gueldenstaedtii (20%), the hybrid H. dauricus × A. schrenckii (13%), and Acipenser transmontanus (12%), while other species jointly contributed 24% to the overall yield. The trends of sturgeon meat and caviar productions of the last 5 years and the forecasts for the future suggest a short-term scenario in which the demand remains lower than the supply. In order to absorb the growing production, the market will have to be expanded by targeting new market segments. K E Y W O R D Saquaculture, markets, production data, sturgeon

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The sturgeon stock in the Sea of Azov is presently maintained by artificial reproduction allowing for the harvest of sturgeons in this basin. Shortened spawning migrations in regulated rivers and long-term artificial selection of the ripest fish at the hatcheries have resulted in high functional maturity of sturgeon spawners in the sea near the river mouth. The traditional technology of artificial sturgeon reproduction is non-effective under modem ecological conditions. The use of ecological and hormonal methods to control seasonal propagation of stellate sturgeon, A.stellatus, Russian sturgeon, A.gueldenstaedti, beluga, Huso huso, and sterlef Aruthenus, make it possible to stagger the sexual cycle of breeders from the various biological groups for early ( 5 months) or later (6 months) spawning. Use of these methods preserves the natural heterogeneity of sturgeon populations maintained through stocking, and also allows for a considerable increase in the quantity of fry reared at the same production base.The use of the synthetic analogue of mammalian gonadotropin-releasing hormone (Gn-RHa) is better for inducing maturity of the ripest brood fishes, especially for stellate sturgeon, in comparison with the traditional pituitary injections. The schedule of injections was determined for the various species and seasons of spawning.Short-term rearing of larvae in ponds (no more than 15 days) and subsequent adaptation to sea water in brackish lagoons (1-5 %) allows for repeated use of nursery ponds in sturgeon hatcheries and a considerable increase in the quantity and survival of sturgeon juveniles in the sea.The restoration of the sturgeon population structure in the Sea of Azov is not possible without developing a genetic collection of the fish under a controlled culture regime. IntroductionThe most effective sturgeon culture in the Azov Sea basin is in the region of the Kuban River. From 1991-1996 five sturgeon hatcheries released 25-27 million juveniles of Russian and stellate sturgeons annually. Approximate yearly catches were 900 tons in

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Stocking hatchery-reared brown trout in different densities into a wild population -a comparison of growth and movementIn spring 2001 and 2002 a small stream was stocked with tagged hatchery-reared yearling brown trout (Salmo trutta), in order to study their influence on the resident brown trout population. The stream was separated into six sections: two sections without stocking, two sections where stocking doubled the trout population and two sections where the fish population was quadrupled. The working hypothesis was that due to food limitation (competition) growth of the wild fish will be negatively influenced by stocking, and wild fish will be displaced by the (possibly more aggressive) hatchery fish. Surprisingly, growth rate of wild and stocked fish of the same age was similar and independent of stocking density. Two main reasons may be responsible for this finding: only a low percentage of the stocked fish remained in the stream, and food was not limited during summer. Only 12-19% of the stocked fish were recaptured after six months, in contrats to 40-70% of one-year old and up to 100% of older wild trout. The wild fish were not displaced by hatchery-reared fish: During summer the wild fish remained more or less stationary, whereas most of the stocked trout had left their release site. The results indicate that in a natural stream stocking of hatchery reared brown trout does not influence negatively growth and movement of the wild fish independent of stocking density. Baer, J. (Fisheries Research Station of Baden-Wu¨rttemberg, Untere Seestraße 81, 88085 Langenargen, Germany). Swimming activity of seabass: comparing patterns obtained in natural environment and in re-circulating tanks under high density Genetic quality of domesticated African tilapia populations Anecdotal and empirical evidence exists for substantial (up to 40%) declines in growth among Oreochromis populations domesticated in both large and small-scale fish farms in Africa. These declines are at least partly attributable to poor genetic management, including inadvertent selection, inbreeding, bottle-necks and founder effects. Due to restricted cash flow and investment capital, genetic management and selective breeding for the improvement of domesticate populations are difficult for small-scale farmers, but feasible on larger-scale farms. In managing domesticated gene pools, feral populations can serve as a broodstock reservoir, making the use of indigenous species advantageous. A development model of large-scale hatcheries producing selected lines of sex-reversed, indigenous tilapia for sale to smaller-scale farmers is proposed as a solution to the problems of poor genetic management in African aquaculture. Brummett, R. E. & Ponzoni, R. (WorldFish Centre, BP 2008, Yaounde´, Cameroon). Polyculture production of juvenile fishes for survival in natureProduction of seed for stock enhancement projects requires consideration of the behavioural quality of the animals to be released in the wild. Our approach to improving behavioural quality of hat...