Effects of slopes and spaces of protrusions in fish ladder for eels on migration rate of Anguilla japonica

In recent year, populations of Anguilla japonica have been decreasing sharply. This decrease is partly because it is estimated to be overfishing of Anguilla japonica, the deterioration of the river environment and so on. Migrating fishes are impeded by weirs and dams in the river. Fishways have been constructed to swimming fish like Plecoglossus altivelis altivelis in order to solve this problem. On the other hand, it is thought that special fishway is necessary for demersal fish like eels. Furthermore, studies on fish ladder for eels haven’t been conducted. In the present study, an investigation on migration rate of Anguilla japonica was conducted under the condition that slope of fish ladder for eels and spaces of protrusions are changed. It was found that migration rates decreased with the increase of slopes and spaces of protrusions. Besides, Anguilla japonica migrated while using protrusions by serpentine movement.The 11th Pacific Symposium on Flow Visualization and Image Processing, 2017, 1-3 December, Kumamoto, Japa

Effects of instillation locations of boulders at bottom of pool-and-weir fishway on migration rate of Zacco platypus

It is important to keep suitable area by boulders in pooland- weir fishway to make the migration rate of fish high. In this study, migrating behaviors of Zacco platypus in pooland- weir fishway were compared with locations of boulders placed on the bottom of pool-and-weir fishway changed. Migration behaviors of Zacco platypus were obtained with the aid of two digital video cameras. It was found that Zacco platypus migrates remarkably uses the space between boulders when boulders were placed on the upper bottom in the pool. It is because the velocity of space between boulders is low compared to other space.The 11th Pacific Symposium on Flow Visualization and Image Processing, 2017, 1-3 December, Kumamoto, Japa

Effects of magnetic force on swimming behavior of isolated Zacco platypus in static water

It becomes quite problematic in fishery that a lot of larval fish are lost due to enter intake gates of weirs and dams. Some techniques with air bubble, electricity and light have been developed to avoid fish from entering intake gates. In recent years, action control techniques of fish with magnet are evaluated. Hutchinson et al. achieved a certain result to prevent the entrance of several species of sharks into longlines by mounting magnets on longlines. Smith & O’Connell showed that magnet worked on Raja clavata to prevent alike. Ward et al. reported the research that Danio rerio which belongs to fresh water fish changed the swimming speed and the swimming direction near the magnets. However, few studies about action control techniques of fresh water fish with magnet have been conducted. In this study, the magnetic flux density of the magnets put on the bottom of the side wall in the circular pool is changed to make clear effects of magnetic force on the swimming behavior of the isolated Zacco platypus in static water. The swimming position, the swimming speed, the fish direction and the turning angle are analyzed by capturing the swimming in the experiment. As a result, Zacco platypus is unaffected by magnet force under the condition of this experiment.The 11th Pacific Symposium on Flow Visualization and Image Processing, 2017, 1-3 December, Kumamoto, Japa

Strength improvement of lime-treated clay with sodium chloride

Lime stabilisation of organic clay has often been studied in the past. However, there is some evidence in the literature that the presence of high concentrations of organic matter in clay soil can lessen the chemical reaction between lime and clay minerals and can have detrimental effects on the engineering properties of soil. Hence, in this paper, the stress–strain behaviour and strength properties of organic soil treated with lime and sodium chloride (NaCl) are analysed. A soil mixture, prepared with 5% lime content and 1·5% humic acid, was stabilised with varying quantities of sodium chloride (0·5, 2·0 and 5·0%). Consolidated undrained and drained triaxial tests were carried out on specimens at curing periods of 7 and 28 d with applied confining pressures of 50 and 100 kPa. Scanning electron microscopy and X-ray diffraction analysis were used to observe the microstructural changes resulting from cementation materials. It was found that the introduction of sodium chloride improved considerably the strength properties of the lime-treated organic clay. The microstructural analysis also confirmed the presence of calcium silicate hydrate in a salt-treated organic clay, which was the main contributing factor to the enhanced engineering properties of the clay

Effects of vegetation density on swimming behavior of Zacco platypus

It is important to secure the rest area for fish. Fish has the ordinary and dark muscle. When fish uses ordinary muscle, fish gets tired. In such a situation, fish needs a rest. In this study, vegetation density in open-channel is changed. The trajectories of Zacco platypus were observed. It was found that Zacco platypus utilized the slow velocity area as rest space. Staying in vegetation area increases with an increase of vegetation density. An approach rate to vegetation area rises with an increase of vegetation density. However, it was not found that clear relationship with a migration rate of Zacco platypus and vegetation density.The 11th Pacific Symposium on Flow Visualization and Image Processing, 2017, 1-3 December, Kumamoto, Japa

The K2-ESPRINT Project. I. Discovery of the Disintegrating Rocky Planet K2-22b with a Cometary Head and Leading Tail

We present the discovery of a transiting exoplanet candidate in the K2 Field-1 with an orbital period of 9.1457 hr: K2-22b. The highly variable transit depths, ranging from $\sim$0\% to 1.3\%, are suggestive of a planet that is disintegrating via the emission of dusty effluents. We characterize the host star as an M-dwarf with $T_{\rm eff} \simeq 3800$ K. We have obtained ground-based transit measurements with several 1-m class telescopes and with the GTC. These observations (1) improve the transit ephemeris; (2) confirm the variable nature of the transit depths; (3) indicate variations in the transit shapes; and (4) demonstrate clearly that at least on one occasion the transit depths were significantly wavelength dependent. The latter three effects tend to indicate extinction of starlight by dust rather than by any combination of solid bodies. The K2 observations yield a folded light curve with lower time resolution but with substantially better statistical precision compared with the ground-based observations. We detect a significant "bump" just after the transit egress, and a less significant bump just prior to transit ingress. We interpret these bumps in the context of a planet that is not only likely streaming a dust tail behind it, but also has a more prominent leading dust trail that precedes it. This effect is modeled in terms of dust grains that can escape to beyond the planet's Hill sphere and effectively undergo `Roche lobe overflow,' even though the planet's surface is likely underfilling its Roche lobe by a factor of 2.Comment: 22 pages, 16 figures. Final version accepted to Ap

Annual variation in the levels of transcripts of sex-specific genes in the mantle of the common mussel, Mytilus edulis

Mytilus species are used as sentinels for the assessment of environmental health but sex or stage in the reproduction cycle is rarely considered even though both parameters are likely to influence responses to pollution. We have validated the use of a qPCR assay for sex identification and related the levels of transcripts to the reproductive cycle. A temporal study of mantle of Mytilus edulis found transcripts of male-specific vitelline coat lysin (VCL) and female-specific vitelline envelope receptor for lysin (VERL) could identify sex over a complete year. The levels of VCL/VERL were proportional to the numbers of sperm/ova and are indicative of the stage of the reproductive cycle. Maximal levels of VCL and VERL were found in February 2009 declining to minima between July - August before increasing and re-attaining a peak in February 2010. Water temperature may influence these transitions since they coincide with minimal water temperature in February and maximal temperature in August. An identical pattern of variation was found for a cryptic female-specific transcript (H5) but a very different pattern was observed for oestrogen receptor 2 (ER2). ER2 varied in a sex-specific way with male > female for most of the cycle, with a female maxima in July and a male maxima in December. Using artificially spawned animals, the transcripts for VCL, VERL and H5 were shown to be present in gametes and thus their disappearance from mantle is indicative of spawning. VCL and VERL are present at equivalent levels in February and July-August but during gametogenesis (August to January) and spawning (March to June) VCL is present at lower relative amounts than VERL. This may indicate sex-specific control mechanisms for these processes and highlight a potential pressure point leading to reduced reproductive output if environmental factors cause asynchrony to gamete maturation or release

Dominant features in three-dimensional turbulence structure: comparison of non-uniform accelerating and decelerating flows

The results are presented from an experimental study to investigate three-dimensional turbulence structure profiles, including turbulence intensity and Reynolds stress, of different non-uniform open channel flows over smooth bed in subcritical flow regime. In the analysis, the uniform flow profiles have been used to compare with those of the non-uniform flows to investigate their time-averaged spatial flow turbulence structure characteristics. The measured non-uniform velocity profiles are used to verify the von Karman constant κ and to estimate sets of log-law integration constant B r and wake parameter П, where their findings are also compared with values from previous studies. From κ, B r and П findings, it has been found that the log-wake law can sufficiently represent the non-uniform flow in its non-modified form, and all κ, B r and П follow universal rules for different bed roughness conditions. The non-uniform flow experiments also show that both the turbulence intensity and Reynolds stress are governed well by exponential pressure gradient parameter β equations. Their exponential constants are described by quadratic functions in the investigated β range. Through this experimental study, it has been observed that the decelerating flow shows higher empirical constants, in both the turbulence intensity and Reynolds stress compared to the accelerating flow. The decelerating flow also has stronger dominance to determine the flow non-uniformity, because it presents higher Reynolds stress profile than uniform flow, whereas the accelerating flow does not