Ograniczanie wyników

Czasopisma help
Autorzy help
Lata help
Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 34

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych:  sturgeon
help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
The possibility of using sturgeon as a stock component during the rearing of pike (Esox lucius L.) fry in tanks was determined. The experiment was conducted in two stages. In the first, pike fry with a body weight of 0.1 g were reared in monoculture and polyculture with a sturgeon component comprising 40 and 80% of the pike biomass. In the second phase, pike fry weighing an average of 3 g were reared in monoculture and polyculture with a sturgeon component comprising 10 and 20% of the pike biomass. The introduction of the sturgeon improved feed utilization and lowered feed conversion ratios from 1.4 to 0.8 in the older pike group (statistically significant difference at P < 0.05). In experiment stage II, the pike fry reared in polyculture with sturgeon attained statistically significant (P < 0.05) higher body growth in comparison with the monoculture variant. Pike survival was the lowest in the monoculture at 72.1 and 91.4% in stages I and II of the experiment, respectively. With regard to the smaller fry, this was due primarily to cannibalism with such losses comprising over 50% of the total losses throughout rearing. Survival in the polycultures was as much as 12% higher. The authors believe that the possibility of rearing these two species together stems from their different behavior and feeding strategy. Another benefit was that the labor-intensive removal of feed not consumed by the pike fry was lowered which meant that there was minimal interference in the tank during rearing.
Chemical deglycosylation (dg) of sturgeon Acipenser gueldenstaedti Br. (alphaGTH) resulted in the loss of 83% of its initial carbohydrate content. It altered also recombinant dgalphaGTH + betaGTH dimer molecule, reducing its immunoreactivity by 30%, and fully blocking the hormonal function. CD spectroscopy showed that deglycosylation led to changes in the secondary structure of dgalphaGTH and in the alpha-beta recombinant. The sugar moiety of sturgeon alphaGTH is suggested to play an important role in maintaining the biological function of the hormone dimer molecule.
Skin mucus and the digestive tract contents of Siberian sturgeon (Acipenser baeri Brandt), feed and water were analyzed during intensive tank rearing. The analyses included the total number of heterotrophic bacteria on common agar at 22°C (TVC 22°C) and 37°C (TVC 37°C), the number of coliforms (TC), fecal coliforms (FC) and fecal streptococci (FS). The water was evaluated for nitrogen cycle bacteria - proteolytic, ammonifying and nitrifying bacteria of phases I and II. The lowest numbers of TVC 22°C (83600 CFU cm⁻³ ) and TVC 37°C (7040 CFU cm⁻³ ) occurred in inflow water. The highest numbers of TVC 22°C (169200 CFU cm⁻³ ) were present in the tanks, while TVC 37°C (7280 CFU cm ⁻³) were the most numerous in outflow water. Statistical analysis confirmed the influence of sturgeon rearing on the densities of these bacteria in the water. No such relationship was detected for sanitary indicator bacteria (TC, FC and FS), the numbers of which did not significantly differ between inflow or outflow water.
Environmental conditions in River Rioni (Georgia) were studied in two seasons, during purported spawning migrations of the common sturgeon. Water temperature and flow velocity were measured in the vicinity of Poti (downstream section of the river) and in the potential spawning areas. At comparable times, water temperature in the spawning grounds was by a few degrees lower than that downstream, the flow velocity being higher and ranging within 1.5 - 2.1 m s-1. As shown by the observations, the area suitable for the sturgeon spawning had shrunk, possibly as a result of river damming. In the areas suitable for the common sturgeon spawning, the river bed was covered by coarse gravel and flattened stones, those measuring up to 30 mm in diameter being most abundant.
The present study evaluated the weight composition of Siberian sturgeon food, the species feeding intensity in a 24-hour cycle (as consumption index I - ‱), and its daily food ration (as a percentage of average fish body mass). The study was conducted on fish in their first year of life which were being reared in a 0.05 ha pond with a maximum depth of 2 m and an average depth of 1.2 m. Chironomid larvae, mainly Chironomus plumosus L., were the principal food component found in the digestive tracts of all the fish in all the samples. Some butterfly and stone-fly larvae were also noted. Feeding intensity reached the highest values at night. Calculated according to Thorpe (1977), the daily food ration of Siberian sturgeon with an average body mass of 20.3 g and at an average daily water temperature of 14.2°C was 5.4% of fish body weight.
Studies were conducted on intensive monoculture and polyculture of wels catfish and sturgeon in ponds. The initial average body weight of the fish in monoculture and polyculture was similar (wels catfish - approximately 100 g; sturgeon-approximately 720 g), and the biomass was equal in each pond (approximately 30.7 kg). The fish were fed trout granulate for two months. The final survival rate was the same in both the monoculture and polyculture (wels catfish - 99.5%; sturgeon - 100%). Statistically significant differences (p < 0.05) were observed between the fish growth in monoculture and polyculture. Wels catfish grew faster in polyculture, with an average body weight of 349.1 g and a specific growth rate (SGR) of 2.0 % day⁻¹. In monoculture these figures were 276.1 g and 1.6 % day⁻¹, respectively. Sturgeon grew faster in monoculture, with an average body weight of 1229.2 g, and an SGR of 0.86 % day⁻¹, while in polyculture these values were 854.2 g and 0.28 % day⁻¹, respectively. The intensive cultivation of wels catfish with sturgeon in pond polyculture influenced their growth, but not survival rates.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.