Vertical distribution of giant jellyfish, <Emphasis Type="Italic">Nemopilema nomurai</Emphasis> using acoustics and optics

Nemopilema nomurai jellyfish, which are believed to complete their development in the East China Sea, have started migrating into the Yellow Sea in recent years. We obtained biomass estimates of this species in the Yellow Sea using bottom trawl fishing gear and sighting surveys over a 5-year period. These methods are effective for obtaining N. nomurai jellyfish density estimates and information about the community distribution near the bottom or surface of the sea. To verify the vertical distributions of giant jellyfish between, we used hydroacoustic equipment, including an optical stereo camera system attached to a towed sledge and an echo counting method with scientific echosounder system. Acoustic and optical data were collected while the vessel moved at 3 knots, from which the distribution and density of N. nomurai jellyfish were analyzed. Subsequently, the camera system was towed from a 7 m mean depth to sea level, with the detection range of the acoustic system extending from an 8 m depth to the bottom surface. The optical and acoustic methods indicated the presence of vertical distribution of 0.11³ (inds/m³) and 0.064 (inds/m3), respectively. However, the vertical distribution indicated that around 93% of individuals occurred at a depth range of 10–40 m; thus, a 2.4-fold greater density was estimated by acoustic echo counting compared to the optical method.     

Geoarchaeological evidence on a Late Bronze Age earthquake,Ohrid Basin (North Macedonia)

Geoarchaeological investigations on the northeastern shore of Lake Ohrid revealed 3.5 m thick deepwater lacustrine sediments overlying terrestrial vegetation macrofossils, worked wood and abundant potsherds dated to the Late Bronze Age (LBA). Distinct contact of deepwater sediment with the sub-aerial weathered limestone bedrock point to a sudden increase in lake level. According to radiocarbon data, catastrophic flooding occurred shortly after 1214 yr bc. Because the area is located in a highly active seismic zone, we propose that this event was caused by tectonically induced, metre-scale coseismic subsidence related to faults bordering the Ohrid alluvial plain. Moreover, this event coincides well with a dramatic switch in the habitation and settlement strategy in the region. More important, however, is the finding that the age of the proposed massive tectonic event and change in habitation lies within the interval of the proposed ‘earthquake storm’ in the eastern Mediterranean dated to 1225–1175 bc. As the Ohrid-Korça zone belongs to the same tectonic province, a relationship between the abovementioned earthquakes and the proposed event can be expected. This research therefore might provide the first direct evidence of a large-scale earthquake event linkable to the LBA collapse of Europe's first urban civilisation in the Aegean.     

Acoustic Characteristic of Sailfin Sandfish (Arctoscopus japonicus) in Dokdo,Republic of Korea

The aim of this study is to determine the acoustic characteristics of sailfin sandfish over a wide frequency range. The acoustic survey was conducted in Fe     

Combating piracy and armed robbery in Asia: The ReCAAP Information Sharing Centre (ISC)

The Regional Cooperation Agreement on Combating Piracy and Armed Robbery Against Ships in Asia (ReCAAP) Information Sharing Centre (ISC) is an international organisation that comprises 14 member countries in the region. Despite its many advantages, the ISC has some weaknesses, which when addressed could bring regional cooperation to a new level and which could make the ISC a model for other regions.     

Notes on the Geological Structure of the Washan-Omeishan Region

I. INTRODUCTION Bordering the SW margin of the Red Basin of Szechuan runs a roughly N-S mountain range which includes such mountains as Washan, Omeishan and Talliangshan (Pl. I) and for the sake of convenience is designated with the name of Liangshan Range. Among these mountains only the geology of the Omeishan region is fairly well known in consequence of the works done by many a geologist; of the Washan region, though had been visited by     

Collectorless flotation of chalcopyrite and sphalerite ores by using sodium sulfide

The flotation of chalcopyrite and sphalerite from copper and copper-zinc ores has been achieved without using thiol-type collectors. Typically, a sulfide ore sample is first treated with sodium sulfide either during grinding or during the preflotation conditioning period, and then the chalcopyrite is floated with frother alone. With a copper-zinc ore, sphalerite is subsequently floated from the chalcopyrite tailings by activating it with copper sulphate. Results of the collectorless flotation tests are comparable to those obtained by using thiol collectors. The mechanisms of selective collectorless flotation are discussed on the basis of differences in the solubilities of sulfide minerals.