Deep Multi-Agent Reinforcement Learning using DNN-Weight Evolution to Optimize Supply Chain Performance

To develop a supply chain management (SCM) system that performs optimally for both each entity in the chain and the entire chain, a multi-agent reinforcement learning (MARL) technique has been developed. To solve two problems of the MARL for SCM (building a Markov decision processes for a supply chain and avoiding learning stagnation in a way similar to the prisoner\u27s dilemma ), a learning management method with deep-neural-network (DNN)-weight evolution (LM-DWE) has been developed. By using a beer distribution game (BDG) as an example of a supply chain, experiments with a four-agent system were performed. Consequently, the LM-DWE successfully solved the above two problems and achieved 80.0% lower total cost than expert players of the BDG

Biological notes on Tachypleus tridentatus (Leach, 1819) in Hiroshima Prefecture, Japan: two species of epibiotic organisms found on adults, and the carcass of a juvenile presumably eaten by a bird

2016年8月5日に広島県竹原市ハチ干潟で発見されたカブトガニ成体に，表在生物のカブトガニウズムシおよびカニエラエボシが確認された．また，2017年9月20日には野鳥に捕食されたと考えられるカブトガニ幼体の死骸が発見された．On August 5, 2016, two epibiotic species, the turbellarian Ectoplana limuli (Ijima & Kaburaki, 1916) and the goose barnacles Octolasmis neptuni (MacDonald, 1869), were found on two adults of the Japanese horseshoe crab Tachypleus tridentatus (Leach, 1819) in Hiroshima Prefecture. On September 20, 2017, the carcass of a juvenile horseshoe crab was found, which had presumably been eaten by a bird.本研究の一部は公益財団法人福武財団「瀬戸内海文化研究・活動支援助成」によって行われたことを明記する

Density of juveniles of tri-spined horseshoe crab Tachypleus tridentatus and characteristics of sediments in the Sone Estuary, Fukuoka, Japan

2017年7月25–27日の大潮最干時刻に福岡県北九州市曽根干潟において，大野川河口，貫川河口，貫川河口−朽網川河口中間点，朽網川河口の底質上に存在するカブトガニ幼体密度を目視よって測定した．幼体は貫川河口付近から沖に向って約300mまでの範囲及び貫川河口−朽網川中間地点にて確認され，その密度は0.063–1.000個体 /m²であった．出現した幼体の前体幅は17.0–60.5 mm（n = 27）であり，第4–8脱皮齢に相当する．粒度分析の結果より，大野川河口は細砂，貫川河口は細粒砂～中粒砂，貫川河口−朽網川河口中間地点は極細粒砂，朽網川河口は極粗粒砂に分類される底質であることが分かった．各調査地点において底質硬度・全硫化物量・強熱減量を測定したところ，いずれも幼体密度との相関はみられなかった．貫川河口域の底質の粒度より算出した中央粒径値は，2016年7月16日に同地点で採取した底質の中央粒径値とは大きく異なっており，貫川河口域での底質環境の変化が示唆された．The density of juveniles of the tri-spined horseshoe crab Tachypleus tridentatus (Leach, 1819) was measured at the lowest tide during the period from 25 to 27 July 2017 at the Sone Estuary in Kitakyushu City, Fukuoka Prefecture. It ranged from 0.063 to 1.000 indiv./m². The highest density was recorded at the mouth of Nuki River. The range of carapace width of juveniles was 17.0–60.5 mm (n = 27), corresponding to the 4th to 8th molts. No juveniles were found at the mouth of the Ono River. Median diameter of sedimentary particles at the habitat area ranged from 0.020 to 0.740 mm. Hardness, total sulfide content and ignition loss were simultaneously measured at each station, but no significant correlation was detected with the density. The median particle size was significantly different from that calculated at the same stations on 16 July 2016, suggesting that the sedimentary environments for the habitat of juveniles in Sone estuary were drastically changed within a year.本研究の一部は公益財団法人福武財団「瀬戸内海文化研究・活動支援助成」によって行われた

An observation of the walking behavior of Podosphaeraster toyoshiomaruae collected from the bank Oshima-shinsone, Kagoshima Prefecture, Japan

トヨシオマリヒトデPodosphaeraster toyoshiomaruae Fujita and Rowe, 2002は体がほぼ球形で，腕が発達しないという特殊な形態を持つ小型ヒトデ類である。鹿児島県奄美大島北西部に位置する大島新曽根水深100-200 m 程度の堆に生息している。この堆はROV で観察するとカイメン類，八放サンゴ類などで覆われている。2017年5月21日に本種の生きた個体が大島新曽根で採集され，管足を伸ばした状態や歩行が観察されたのでその行動を記載した。管足を体内にしまった状態とは異なり，体がやや口・肛門軸方向に扁平になり，約1.65 cm/min の速度で歩行した。通常の腕の発達したヒトデ類の歩行速度と比較すると相対的に著しく遅い。管足には少なくとも2種類が認められ，歩行用と感覚用と考えられる。The podosphaerastrid asteroid Podosphaeraster toyoshiomaruae Fujita and Rowe, 2002 is small-sized, nearly spherical in shape. The species exclusively inhabits on the bank Oshima-shinsone at depths of 100 to 200 m, northwest of Amami-Oshima Island, Kagoshima Prefecture, Japan, where the bottom is entirely covered with sponges, octocorals, and hyrozoan polyps with patches of sandy bottom. The bottom conditions were clearly observed with a ROV on September 29, 2009. A living specimen was collected from this locality on May 21, 2017. During locomotion by tube feet, the body was depressed dorso-ventrally in contrast with the spherical body shape with tube feet unexpanded. The locomotion rate of the specimen was about 1.65 cm/min. Two types of tube feet were identified. Presumably one is for locomotion with a sucker terminally, while the other for sensing.本研究の一部は日本学術振興会科学研究費（基盤研究C，No.16K07825，代表 大塚攻），国立科学博物館総合研究「黒潮に注目した地史・生物史・人類史」によって行われた

沿岸性魚類スズキにおける河川・河口域の重要性

京都大学0048新制・課程博士博士(農学)甲第18337号農博第2062号新制||農||1023(附属図書館)学位論文||H26||N4844(農学部図書室)31195京都大学大学院農学研究科応用生物科学専攻(主査)教授 荒井 修亮, 教授 山下 洋, 准教授 田川 正朋学位規則第4条第1項該当Doctor of Agricultural ScienceKyoto UniversityDFA

Upstream migration mechanisms of juvenile temperate sea bass Lateolabrax japonicus in the stratified Yura River estuary

Hydrographic conditions and distributions of juvenile temperate sea bass Lateolabrax japonicus were observed in early spring from 2009 to 2012 in the Yura River estuary, which is highly stratified due to its small tides and consequent seawater intrusion into the bottom layer of the river as a salt wedge. In all four studied years, the upstream expansion of their distribution coincided with the timing of the salt wedge intrusion from the lower to upper estuary, indicating that juvenile fish used salt wedge intrusions to ascend the estuary in early spring. However, juveniles sometimes remained in the nearshore area even when the salt wedge intrusion had already occurred, indicating that other triggers are also likely to be necessary. We therefore evaluated the effects of temperature on upstream migration behaviors. The relationship between the mean temperature they experienced from hatch until starting the ascent and mean age of each cohort at the upstream migration fitted with the law of effective cumulative temperature. Most cohorts ascended the river at an effective cumulative temperature of approximately 500 °C–days. This suggests that higher temperatures would lead to a shorter period prior to the upstream migration

Partial migration of juvenile temperate seabass Lateolabrax japonicus: a versatile survival strategy

Partial migration describes intrapopulation variation in the migratory behavior, i.e. some individuals from a population migrate to low-salinity river areas, while others remain in coastal areas. This paper reviews the partial migration pattern of juvenile temperate seabass Lateolabrax japonicus, which is a migration pattern not commonly seen in Japan. Seabass spawn offshore, and eggs and larvae are transported to coastal areas. Some of these juveniles then ascend rivers, while others remain in coastal areas. Juveniles efficiently use physical structures in their habitat; they use tidal currents to ascend rivers in macrotidal estuaries, while they use the salt wedge in microtidal estuaries. Once juveniles ascend the river, they can feed on the abundant prey and attain more rapid growth than those remaining in coastal areas. As estuaries are highly productive areas, they play significant roles as nurseries for juveniles of various fishes. However, compared with coastal areas, the relative area of estuaries is considerably smaller and its environmental conditions are more variable. For example, nearly 40% of adult seabass in Tango Bay were estimated to use estuarine areas as a nursery, while the other 60% use coastal areas during their juvenile stage. Using both estuaries and coastal areas through partial migration during the juvenile stage is concluded to contribute to the stabilization and yield of seabass populations

Freshwater migration and feeding habits of juvenile temperate seabass Lateolabrax japonicus in the stratified Yura River estuary, the Sea of Japan

Juvenile temperate seabass Lateolabrax japonicus were sampled along the Yura River estuary from April to July 2008 to determine their distribution and feeding habits during migration within a microtidal estuary. Throughout the sampling period, juvenile seabass were distributed not only in the surf zone, but also in the freshwater zone, and they were particularly abundant in areas with aquatic vegetation in the freshwater zone. This distribution pattern suggests that the early life history of the temperate seabass depends more intensively on the river (freshwater) than previously considered. Small juveniles in the freshwater zone fed on copepods and chironomid larvae and upon reaching a standard length (SL) of approximately 20 mm did they fed on mysids. In contrast, juveniles (approx. 17–80 mm SL) in the surf zone fed mainly on mysids