Microspectrophotometry and immunocytochemistry with several antivisual pigment antibodies were used to study visual cells of the Siberian sturgeon, Acipenser baeri Brandt. The retina contained rods and three morphological types of cones: large cones with oil drops, small cones with oil drops, and cone-like cells without oil drops. Rods and cone-like drop-free cells were found to possess porphyropsin-549, while the large oil drop-bearing cones contained red-sensitive (P613), green-sensitive (P542), and blue-sensitive (P462) visual pigments. The immunocytochemical staining pattern with three antibodies to visual pigment proteins also revealed one visual pigment in rods and three visual pigments in cones. Rods were labeled with all three antibodies, while the majority of large cones (type I), presumably the red-sensitive ones, were negative with the polyclonal serum AO against bovine opsin. A less-frequently occurring large cone type (type II) was stained by all three antibodies including mAb COS-1 specific to middle-to-long-wave visual pigments in birds and mammals, and is thought to be green-sensitive. An even less-frequent large cone type (type III, probably the blue-sensitive one) did not bind COS-1. The small cones with oil droplets showed immunoreactivities similar to either type II or type III cones. The oil drop-free small photoreceptor exhibited a staining pattern identical with that of rods. These results indicate that the immunocytochemical approach can be used to reveal photoreceptor-specific neural connections in the sturgeon retina.

The article presents new results of stable isotope analyses made on animal and human bones from the Mesolithic–early Neolithic sites of Lepenski Vir and Vlasac in the Danube Gorges of the Balkans. It reconstructs the food web for the region during these periods on the basis of stable isotope analyses of mammal and fish species found at Vlasac. These results are compared to measurements made on human burials from the two sites. In the light of these new results, the article also discusses interpretations provided by previous isotopic studies of this material. It concludes that great care is required in the interpretation of stable isotope results due to inherent methodological complexities of this type of analysis, and suggests that it is also necessary to integrate stable isotope results with information based on the examination of faunal remains and the archaeological context of analysed burials when making inferences about palaeodietary patterns.

Culture of sturgeons in Russia began in the second half of the 19th century. During the first part of the 20th century, a significant research effort was devoted to the control of reproduction and the rearing of larvae mostly for stock enhancement purpose in rivers. Large-scale construction of hatcheries began in the 1950s after the damming of rivers, and by the 1980s over 130 million 1–3-g juveniles per year were being produced from wild broodstock. Presently, the production is 100 million juveniles. Emphasis is now on optimising stocking results through consideration of fish-specific factors (e.g. behaviour, fitness, size, balance between species) as well as environmental variables (food availability, release sites, salinity, precipitation regime). Food fish production of sturgeon (market size is 1.5–2.0 kg is just beginning using captive broodstock and new growing technologies. In 2000, farm production was about 1650 t, which was higher than sturgeon landing from wild fisheries (1500 t declared in 2000).

The pattern of ammonia excretion was examined in the Siberian sturgeon, Acipenser baeri, during starvation. For different weight groups (60 g to 2 kg), this excretion decreased rapidly to reach a constant level of 32 mg NH4-N.kg-1.day-1 after 8 days of fast. This minimum is an estimation of the Endogenous Nitrogen Excretion (ENE). No diurnal pattern was observed in the ammonia excretion or oxygen consumption (28.6 ± 3.2 mg O2.kg-1.h-1, mean ± sd) of fasted fish. These data appear to indicate that the basal metabolism is very low in the Siberian sturgeon and that the nycthemeral cycle is only the result of exogenous nutrition.

Sex steroid levels were determined in various commercial fish meals and complete diets. The results obtained demonstrate that estrone (E1), 17 β-estradiol (E2) and androgens (A) (testosterone and 11-ketotestosterone), are present in diets in high quantities (up to 935±350 ng/100 g for E2, 615±190 ng/100 g for E1 and 1100±120 ng/100 g for A) and with considerable variation both between different diets, and between different batches of the same diet. These high levels of sex steroids are thought to influence the sex steroid plasmatic levels and plasma vitellogenin content in fish. Plasma sex steroid assays in the Siberian sturgeon Acipenser baeri show that plasmatic 17 β-estradiol levels are never significantly different between males and females at various stages of oogenesis and spermatogenesis, except in 6 year old females in stage IV, which corresponds to the maximum incorporation of vitellogenin. In males the plasma 17 β-estradiol levels are exceptionally high and induce vitellogenin synthesis, as demonstrated by various chemical and immunological techniques.