Effect of Antimicrobial Peptides on the Growth and Immunity of Swamp Eels

This study aimed to investigate the effect of different levels of antimicrobial peptides (AMPs) supplementation in the diet feed on growth performance, survival rate, biochemical parameters in swamp eels. Healthy fishes were randomly assigned to five groups feeding with different supplementation of AMPs (0, 200, 400, 600, or 800 mg/kg) in diets for 68 days. Results showed that relative weight gain, feed coefficient and survival rate were significantly (p<0.05) increased by supplementation of AMPs in feed. Level of protein (TP), triglyceride TG, alanine transaminase (ALT), alkaline phosphate (ALP), acid phosphate (ACP), superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) in the serum were significantly (p<0.05) improved in all AMPs treatments, while no significant difference was found between the control and AMPs 200 mg/kg. AMPs supplementation significantly enhanced (p<0.05) the survival rate and immune protection in swamp eels after challenged with Aeromonas hydrophila compared to the control group and eels fed with AMPs 800 mg/kg had the highest survival rate and immune protection (32.50 and 85.71%, respectively). The diets containing AMPs enhanced the survival rate, immune ability, and antioxidant capacity in swamp eels, indicate that an appropriate dosage of AMPs can be used as a potential alternative to antibiotics in swamp eels.

Growth of rainbow trout (oncorhynchus mykiss) in the conditions of Tashkent province, Uzbekistan

Rainbow trout is a new fish farming object for Uzbekistan, the adaptability of which (first of all, growth) to local conditions should be carefully studied. We analyzed the growth of rainbow trout in the conditions of flowing pools and cages in the foothill zone of Tashkent province of Uzbekistan. From March to October, the water temperature in the Khojikent reservoir varied from 4.9 to 13.1 °C, the amount of dissolved oxygen was 8.4 to 11.5 mg/l, and the pH was 7.40 to 7.67. In the flowing basin, the temperature was 15-18 °C, pH 7.2-7.5, the amount of dissolved oxygen 6.1-11.2 mg/l. The conditions of the foothill zones of Uzbekistan in terms of water quality are favorable for the development of trout breeding. During the season, fish in cages increased from 250 g to 623 g, in pools from 25 g to 390 g on average. The waste was 1.7%. The actual fish productivity of the basin is 39 kg/m3, the cage is 30 kg/m3 and the feed coefficient in the basin is 1.2, in the cages - 1.09.

The effect of deformation of flow part of elastomeric elements of self-acting valves on characteristics of low-speed long-stroke compressor stages

The results of the study of the influence of changes in the area of the flow section in the seat of selfacting valves with elastomeric elements on the characteristics of low-speed compressor stages are presented. A method of experimental research of low-speed compressor stages with the possibility of obtaining instantaneous parameters of the gas state in the working chamber of the stage and its integral characteristics and an experimental stand for its implementation have been developed. The results of comparative experimental studies have confirmed the effectiveness of the valve design with a variable cross-sectional area of the seat in comparison with known designs — an increase in the feed coefficient and isothermal indicator efficiency is at least 10...15%.

PECULIARITIES OF CULTIVATION OF THE ORANGE-FIN RAINBOW TROUT ONCORHYNCHUS MYKISS (WALBAUM, 1792) IN CONDITIONS OF THE SULAK CANYON

The article has, for the first time in 20 years, presented the data on weight growth of the rainbow trout, grown in cag-es, in the territory of the Republic of Daghestan. The experiment has been conducted on the 5000 fries of the rainbow trout with an average weight of 41 gr. throughout the spring period. Tested was the original feed of the simplified rec-ipes and the minimal equipment costs for its production. As a result, it was proved that in the territory of the Sulak canyon there are all opportunities for growing commercial fish in cages. The results of the study showed that by the end of the experiment, the average weight of rainbow trout fry had reached 80 gr., the feed coefficient was 0,57–0,60%, while the loss of the fry was not observed. That indicates good quality of the food and favorable natural conditions for growing fish.

Trophic analysis of the fish community in the Ciénega Churince, Cuatro Ciénegas, Coahuila

Fish diets were analyzed to evaluate the dynamic trophs of the fish community in the Churince wetland system of the Cuatro Ciénegas, where the fauna consists of nine species: endemic, native and introduced. In nine sampling events (between February 2011 and May 2014) 556 specimens of all nine species were collected. Stomach contents were analyzed and the Relative Importance Index (IRI) was calculated. The feed coefficient (Q) of the diets and the accumulated trophic diversity (Hk), as well as the amplitude of the trophic niche were evaluated. Feeding strategies in the fish community were found to be eurifagic. The main foods in general were insects, crustaceans, gastropods, plants and teleosts. According to the average linkage method, four functional trophic groups were defined, with no higher consumption species; nevertheless all were regulators, mainly invertebrates. Therefore, the chain reaction in food control was higher from top to bottom, meaning a downwards dietary control.

Environmental impact of nutrients from nordic fish farming

During the last 20 years there has been an interesting development of the Nordic fish farming, with regard to the feeding and farming technology and to the increase in production quantities. During the period 1974-1994 the production increased from 15,800 to about 250,000 tonnes/year. In 1974 the major part of the production was in Denmark, and in 1994 the major part was in Norway. The nutrient impact of fish farming on surrounding sea areas is mainly a function of the feed coefficient, the feed composition and metabolic processes in the fish. The comprehensive development of the feed composition and the feeding technology has resulted in reduced load of unmetabolized nutrients from fish farms, calculated per tonne fish produced. In 1974 the mean Nordic feed coefficient was 2.08 and in 1994 the coefficient was 1.25. Feed coefficients of 1.0-1.1 are now reported for Danish and Norwegian freshwater and marine fish farms. The nitrogen (N) and phosphorus (P) content of the feed has decreased, in addition the quality of the nutrient substances in the feed has changed, especially for N. The N content has decreased from 7.8 to 6.8% during the period 1974-1994 and the content of P has decreased from 1.7 to 0.7% during the same period. This development of the feed coefficient and the feed composition has resulted in a present load from a typical Nordic fish farm of 55 kg N and 4.8 kg P/t fish produced. The figures for 1974 were 132 kg N and 31 kg P/t fish produced. The Nordic fish farming production in 1994 resulted in a load of about 13,750 t N and about 1,200 t P on the actual recipients. The load from the Swedish, Finnish and Danish fish farming operations, with the Baltic Sea and the Skagerrak as the recipients, is negligible in comparison with other pollution sources. The quantities of N and P from the fish farming are equal to 0.5% of the atmospheric deposition on the sea surface and 3% of the atmospheric P load. Norwegian, Icelandic and the Faroe Islands fish farming operations are using the North Sea and the Norwegian Sea as the recipients. However, the nutrient load from single fish farms in certain coastal and inland water bodies can be significant and must be considered in the impact assessment together with other sources.