Efficacy of clove oil and ethanol against Saprolegnia sp. and usability as antifungal agents during incubation of rainbow trout Oncorhynchus mykiss (Walbaum) eggs

Inhibitory concentrations of clove oil and ethanol against growth of Saprolegnia sp. hyphae were screened by a modification of the hemp (Cannabis sativa L.) seed MicroPlate (HeMP) method and their usability as antifungal agents during incubation of rainbow trout Oncorhynchus mykiss eggs was tested. In vitro experiment showed that in continuous static exposure, clove oil at 100 mg L^?1 significantly inhibited the growth of Saprolegnia, whereas in bath exposures, clove oil at 500 mg L^?1 had no significant effect at any exposure time tested (15, 60 and 240 min), but clove oil at 10 000 mg L^?1 significantly inhibited growth at all exposure times. Clove oil and ethanol treatments had no visible effects on the onset or spread of the fungus during incubation of rainbow trout eggs. Clove oil at 1000 mg L^?1 resulted in 95–100% mortality before the eyed stage was reached. Sublethal concentrations of clove oil and ethanol had no effects on the development rate of the embryo or growth and yolk utilization efficiency after hatching. This study suggests that clove oil and ethanol may not be options in controlling aquatic fungi infestations during incubation of rainbow trout eggs.     

Longer wavelengths of light improve the growth, intake and feed efficiency of individually reared juvenile pikeperch Sander lucioperca (L.)

We tested the effects of monochromatic light on the specific growth rate (SGR), feed intake and feed efficiency (FE) of juvenile pikeperch, Sander lucioperca (L.). Pikeperch were reared individually for 42 days in aquaria covered with blue, green, yellow or red gelatin filters or white paper (control; n =5). Linear regression analysis indicated a significant positive effect of longer wavelengths of light on the condition factor (CF), FE and SGR. The final weight, SGR and CF were significantly higher in fish reared under red than under white light, and FE was better under green, yellow and red light than under white light (Dunnett's post hoc test, P <0.05) while blue was comparable to white light in terms of the measured parameters. After the growth trial, the spectral sensitivity of photoreceptor cells in the retina was tested using microspectrophotometry, which revealed the presence of rods with λ_max at ca. 530 nm and two cone classes, absorbing maximally at ca. 535 and 603 nm, all containing a porphyropsin-based pigment. These results suggest that the presence of mid and long wavelength-sensitive cones enhances visual sensitivity under mid-wavelength and long-wavelength environments, and thus supports the finding that longer wavelengths of incoming light can improve FE and SGR of the cultivated pikeperch.     

Serum glutathione peroxidase activity and blood selenium in pigs

Blood serum glutathione peroxidase activity and blood selenium concentration were measured in blood samples from pigs subjected to experimentally induced selenium deficiency and dietary selenium supplementation on graded levels. A highly significant correlation between blood selenium and serum GSH-Px activity in pigs, especially in selenium deficient pigs, was demonstrated. There was also a strong relationship between blood selenium concentration and serum GSH-Px activity in pigs receiving dietary selenium at graded levels. Serum GSH-Px activity exhibited an excellent close-response relationship to dietary selenium. Linear regression analysis showed that the increased serum GSH-Px activity was a function of the dietary selenium concentration. The fitness of serum in monitoring slight changes of the selenium status of pigs with help of the estimation of GSH-Px activity was discussed. The measurement of serum GSH-Px activity seems to provide a useful and rapid means for defining selenium requirements and for identifying selenium deficiency in growing pigs.     

Meteorological variability of the wet and dry deposition of sulphur and nitrogen compounds over the baltic sea

The dry and wet deposition of N and S compounds to the Baltic Sea Basin were assessed using daily concentration measurements of air and precipitation concentrations, and actual meteorological data on precipitation, daily wind speed and wind direction, as well as the buoyant fluxes at the air- sea interface. The data cover the period 1980–86. Both concentrations and deposition levels show distinct south-north gradients and strong seasonal variability. Dry deposition is an important contribution in the case of S (25 to 80%) but is less significant for the N compounds (10 to 30%). The contribution of particles to dry deposition is negligible for S, equivalent to the gaseous contribution for oxidized N and about 10 to 20% for reduced nitrogen compounds. The obtained total annual deposition of about 1.4 to 1.8 g(S) m^?2 for the S compounds, and 1 g(N) m^?2 for the N compounds are comparable with, but on the upper side of, previous empirical and model estimates.     

Effect of dinoseb on nitrogen fixation of red clover (Trifolium pratense)

The effect of the herbicide dinoseb (2-sec-butyl-4,6-dinitrophenol) on the symbiotic nitrogen fixation of red clover (Trifolium pratense cv. Venla) was studied in field, greenhouse and laboratory experiments. In the field, the herbicide reduced the levels of nitrogenase (C₂H₂) activity of the plants up to 18 days after treatment, but increased the yields compared to hand-weeded and unweeded controls. Rhizobium strains isolated from root nodules of plants treated with dinoseb showed resistance to the herbicide when grown on laboratory media containing dinoseb. However, in a pot experiment, inoculation with a strain which grew in the presence of 200 μg dinoseb ml^?1 did not improve the performance of red clover treated with dinoseb. In the pot experiment dinoseb inhibited nitrogenase activity when sprayed on the leaves, but not when added to the growth medium. Application of starter nitrogen did not influence the effect of dinoseb. The results suggest that dinoseb did not act directly on the nodules, but affected nitrogen fixation by damaging the photosynthetic parts of the plant.     

Indirect estimation of stomach volume of rainbow trout Oncorhynchus mykiss (Walbaum)

The main hypothesis of this study was that if stomach volume is correlated with food intake it can be estimated without laborious and destructive direct measurement. Rainbow trout, Oncorhynchus mykiss (Walbaum), ca. 500–1300 g, were starved for 1, 4, 8 or 16 days at 15°C after which they were fed in excess with dry pellets containing known amounts of X‐ray‐dense markers. Immediately after feeding the fish were killed, X rayed and weighed. Then the stomach was dissected, its contents removed and weighed, and stomach volume was measured. X‐ray plates were developed and feed intake was estimated based on the amount of marker. All measured variables correlated positively with stomach volume. The best fit for linear regression models was obtained for fish starved for 4 days, where stomach content (dry mass) explained 94%, food intake (based on X‐ray measurement) 77% and fish mass 62% of the variation in stomach volume. However, as stomach content measurement can be a lethal, or at least very stressful, event for the fish, the accuracy of food intake measurement (X‐ray) could be increased using multiple regression. In multiple linear regressions, R²‐values varied between 0.79 (16‐day starvation) and 0.91 (1‐day starvation) with food intake and fish mass as explanatory variables for stomach volume. These results indicate that the stomach volume in rainbow trout can be estimated satisfactorily using indirect methods, which are not detrimental to the fish, although feeding history may affect the accuracy of the estimates.     

Formal and informal institutions and their hierarchy in the regulation of the forest lease in Russia

The aim of this study is to identify and analyse the institutionalarrangements that regulate the forest lease and related marketsof industrial timber in Russia. A theoretical framework is derivedfrom institutional economics. Institutions, their hierarchyand cohesion are surveyed at constitutional, collective-choiceand operational levels. The organization of the long-term forestlease and its contribution to the sustainable forest managementand development of forest industries are described and regionaldifferences in the organization of forestry are tested. In addition,the expected impacts of the new federal Forest Code are analysed.