Session E5: What Should We Know About Behavior of Sturgeons to Provide Their Efficient Passage?

Abstract: To provide passage of migrating sturgeons through dams, we have, first of all, to monitor and control their behavior in the water flow. To achieve this, we have to know following behavioral and ecological traits such as: rheoreaction, threshold and critical swimming velocity, swimming endurance, behavior in the flow velocity gradient, diel and seasonal patterns of spawning migrations, and vertical and horizontal distribution of migrating sturgeons. Such information is needed to determine optimum flow velocities attracting fish to the entrance of a fish pass (FP), FP operation regime, duration of attraction of migrants, location of the entrance to FP downstream the dam, and conditions at the fish release site upstream the dam. Since 1955 to 2005, 16 FP, to enhance fish spawning migration, were built at 11 large dams in the basins of rivers Volga, Don, and Kuban. One of the main functions of the FP was to facilitate spawning migration of sturgeons - Huso huso, Acipenser gueldenstaedti, A. stellatus, and A. ruthenus. Several types of FP were built: hydraulic (1 FP) and mechanic (2) fish lifts; fish locks (10), natural (spawning) bypass channels (2), and experimental floating FP (1). Most of them were efficient. Efficiency of some FP was as high as 67% (of the number of approached fish; river Don – Kochetovskii powerplant). The number of sturgeons that passed through the Volgogradskaya dam (river Volga) reached 60000 ind. per year (1967); 2050 ind. (Kochetovskaya dam, 1975); 2130 ind. through the Fedorovskaya dam (river Kuban, 1987). In the 1990s, the number of sturgeons in the Russian rivers decreased dramatically, mainly due to heavy poaching. This resulted in an abrupt decrease of the number of passed fish. In consequence, operation of some FP was suspende

IMPROVING THE EFFICIENCY OF MASTERING DISTRIBUTED INFORMATION SYSTEMS IN A VIRTUAL COMPUTER LAB BASED ON THE USE OF CONTAINERIZATION AND CONTAINER ORCHESTRATION TECHNOLOGIES

This article discusses issues surrounding the training of specialists in distributed information systems using innovative methods and technologies in a virtual computer lab environment with an integrated knowledge management system. The article clearly shows how complex knowledge, skills, and professional competencies should be taught to IT specialists. It provides a detailed exploration of the architecture of the Virtual Computer Lab (VCL) and describes the successful experience of using the VCL in classes taught by the Department of Systems Analysis and Control at the Dubna State University. The new practice with containers is different compared to hardware virtualization case and effectively complements it for a wide range of practical educational tasks dedicated to the mastering distributed information systems in a virtual computer lab. For the underlying operating system kernel can be used for all containers and improves payload on the north of a similar configuration. The article provides a detailed description of containerization technology to improve the efficiency of IT-training and features of container management in a distributed environment

Allee effect in a manipulative parasite within poikilothermic host under temperature change

Temperature and intraspecific competition are important factors influencing the growth of all organisms, including parasites. The temperature increase is suggested to stimulate the development of parasites within poikilothermic hosts. However, at high parasite densities, this effect could be diminished, due to stronger intraspecific competition. Our study, for the first time, addressed the joint effects of warming and parasite abundances on parasite growth in poikilothermic hosts. The growth of the common fish parasite larvae (trematode Diplostomum pseudospathaceum) within the rainbow trout at different infection intensities and temperatures (15°C and 18°C) was experimentally investigated. The results showed that temperature was positively correlated with both parasite infection success and growth rates. The growth rates increased much more compared to those in many free-living poikilothermic animals. Atypically for a majority of parasites, D. pseudospathaceum larvae grow faster when abundant (Allee effect). The possible causes for this phenomenon (manipulation cost sharing, etc.) are discussed in this study. Importantly, limited evidence of the interaction between temperature and population density was found. It is likely that temperature did not change the magnitude of the Allee effect but affected its timing. The impact of these effects is supposed to become more pronounced in freshwater ecosystems under current climate changes.peerReviewe

Trematode cercariae as prey for zooplankton : effect on fitness traits of predators

Removal of parasite free-living stages by predators has previously been suggested an important factor controlling parasite transmission in aquatic habitats. Experimental studies of zooplankton predation on macroparasite larvae are, however, scarce. We tested whether trematode cercariae, which are often numerous in shallow waters, are suitable prey for syntopic zooplankters. Feeding rates and survival of freshwater cyclopoids (Megacyclops viridis, Macrocyclops distinctus), calanoids (Arctodiaptomus paulseni), cladocerans (Sida crystallina) and rotifers Asplanchna spp., fed with cercariae of Diplostomum pseudospathaceum, a common fish trematode, were studied. In additional long-term experiments, we studied reproduction of cyclopoids fed with cercariae. All tested zooplankton species consumed cercariae. The highest feeding rates were observed for cyclopoids (33 ± 12 cercariae ind -1 h -1 ), which actively reproduced (up to one egg clutch day -1 ) when fed ad libitum with cercariae. Their reproductive characteristics did not change significantly with time, indicating that cercariae supported cyclopoids' dietary needs. Mortality of rotifers and cladocerans was high (25-28% individuals) when exposed to cercariae in contrast to cyclopoids and calanoids (<2%). Cercariae clogged the filtration apparatus of cladocerans and caused internal injuries in predatory rotifers, which ingested cercariae. Observed trophic links between common freshwater zooplankters and cercariae may significantly influence food webs and parasite transmission in lentic ecosystems. © 2018 Cambridge University Press.peerReviewe