The spawning habitat of the endangered Chinese false gudgeon, Abbottina rivularis, was investigated in an irrigation channel near the Ushizu River, northern Kyushu Island, Japan, from March to May, 2012. Sixteen nest sites were identified from early April to mid-May. A generalized mixed liner model incorporating nest presence/absence data and several environmental parameters, disclosed the environmental characteristics of the spawning habitat of the species, indicating the probability of occurrence of a nest with distance from the channel bank, current velocity and emergent plants. The results suggested that the maintenance of low current velocity and few or no emergent plants near the banks were most important for conservation of the spawning habitats of A. rivularis.

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　The reproductive cycle of Abbottina rivularis was investigated at Katada Naiko on the shore of Lake Biwa in Shiga Prefecture, Japan. By casting net sampling, specimens were collected every season from August 2001 through June 2005. Of the 37 female specimens collected from November through May, 34 were mature. The females collected between late February and mid- April exhibited a large body size and high gonadosomatic index （GSI）. Of the 31 male specimens collected from October through May, 30 were mature. All the males collected between February and May had pearl organs on their pectoral fins, and some males collected between March and May exhibited a large body size and high GSI. These results suggest that at Katada Naiko, the reproductive cycle of A. rivalaris occurs over 1.5 months from late February through mid-April.

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カマツカ亜科魚類の自然分布は, ベトナムのメコン川以北のアジア大陸東部とされていたが, 新たたメコン川流域からを3個体採集したので, 形態的特徴を記載するとともに, 生物地理学的観点から考察した.

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Fifteen specimens of the Chinese false gudgeon Abbottina rivularis were collected from three rivers in the Lake Biwa–Yodo River system, Kyoto Prefecture, Japan for the first time in 38 years. A molecular phylogenetic analysis of mitochondrial cytochrome b gene sequences indicated that the specimen haplotypes completely matched two haplotypes included in the Honshu clade of the Japanese lineage, suggested as indigenous to Japan in a previous study. Further surveys are necessary to reveal the origin and distribution of the species in Kyoto Prefecture, and future conservation requirements, in addition to progressing biogeographic studies in the Kinki region.

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In this paper the writer deals with the breeding habits of the fresh-water suker, Abbottina rivularis (BASILEWSKy), a small cyprinoid fish. The usual habitats of the fish are the slow streams with muddy bottom. The spawning season lasts from beginning of March to early May. In the breeding male numerous horny tubercles appear on the snout, anterior part of the cheek, pre-opercle region and on the outer margin of pectoral fins. Dusky and yellow nuptial coloration also appears on the body.
The male fish prepairs a nest on the muddy bottom in the shape of a round, shallow depression, 20-40 cm. in diameter and 3-5 cm. in depth. In this nest about 2, 000-4, 000 eggs are deposited, over which the male parent fish eagerly keeps guard until the hatched larvae attain the end of the post-larval stage, about 10mm. in total length. The egg is spherical in shape and about 1.4mm. in diameter, with a jelly-like coating of about 1mm. in thickness. The surface of the jelly coat is covered with mud.

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　菊池川では氾濫原に依存して生息する魚類（氾濫原依存魚種）が激減しており，氾濫原依存種を保全するためのワンドやたまり等の河道内氾濫原水域の造成等の対策が必要である．本研究では，菊池川における氾濫原依存魚種の保全にむけた知見を得るため，河道内氾濫原水域をタイプ分類し，それぞれが有する氾濫原依存魚種生息場としての機能を評価した．その結果，固定砂州たまりや水域面積の大きな固定砂州ワンドで氾濫原依存種が多く確認され，特に，氾濫原依存種で絶滅危惧種であるタナゴ類，ミナミメダカ，3種の保全には，固定砂州上のワンド・たまりが重要であることが示唆された．一方で，砂州上に形成されたワンド（砂州尻ワンド，砂州中腹ワンド，砂州頭ワンド）は，オイカワやカワムツの稚魚の生息場として機能していた．

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In this paper the authors describe a conclusion regarding the result of comparative ob-servations on the pharyngeal bones and their teeth in four subfamilies, eighteen genera and thirty species of Japanese cyprinids.
Though there are some variations, relative length of the pharyngeal is fairly constant, and pharyngeal bone length in standard body length of the fish will make one of specific characters of the fish (Table 1).
In all Japanese cyprinids, the rate of the breadth in the length of pharyngeal bones is in the range of 5.2 ?? 3.0 In general, fishes with long pharyngeals tend to be carnivorous, or fishes with short and broad pharyngeals are usually inclined to be herbivorous (Table 2).
The length of posterior and anterior limbs equal in length in almost all species, or the former slightly longer than the latter, while the anterior limbs longer than the posterior ones in five species of leuciscine fishes.
The rate of elongation to anterior direction of pitted surface of the pharyngeal will make one of specific characters of the fish.
In all species, pharyngeal bones of the fish always having anterior angle, but posterior angle indistinct or not to be found.
Pharyngeal bones having one to three rows of teeth. In the first row with three to five teeth, the second row without or with one to five teeth and the third row without or with two teeth. (Table 5-7)
The authors have established a key to Japanese cyprinids subfamilies according to the characters of pharyngeal bones and their teeth.

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本研究では、日本を含むアジアを中心に繁栄しているコイ科カマツカ類の信頼性の高い系統関係を示すために、近年報告された新種や新たな種内系統を含めた日本産カマツカ類全種を用いて、ミトコンドリアの Cytb 遺伝子と COI 遺伝子及び核の RAG1 遺伝子の塩基配列を決定して系統解析を行った。また、先行研究と当研究室の研究の間でみられたタモロコのCytb遺伝子の塩基配列の相違について、その矛盾を解決するために系統解析を行った。その結果、カマツカ類の属の分類は支持され、属間の関係もこれまでの分子系統解析の結果に概ね一致した。カマツカ類の起源は約 3000 万年前と推定され、Liu et al.（2010）の分岐年代推定の結果（約 2900 万年前）にほぼ一致した。タモロコの塩基配列の10 %の相違は、各々の研究で用いたタモロコが、別種の可能性が高い異なる種内系統に属していたためであることが明らかになった。

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This study aims to acquire basic knowledge for the conservation of floodplain dependent species at the Kikuchi river. We investigated water quality, physical environment and fish of the artificial off-channel habitat inflow of groundwater has been constructed in March 2014. The artificial off-channel habitat was confirmed that it is functioning as the habitat of Cobitis kaibara and Lethenteron reissneri the floodplain dependent species by inflow of groundwater.

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琵琶湖の内湖における生物多様性減少機構を明らかするため，魚類相の定量調査を堅田内湖で実施した．標本は2001年8月から2006年7月の5ヵ年にわたり投網で集めた．1年目と2年目ではフナ属魚類，モツゴ，タイリクバラタナゴの3種が優占種であった．5年の調査期間中，この3種が全体に占める個体数の割合は83.3%，84.3%，68.9%，18.6%，および15.5%と激減し，一方で侵略的外来種のブルーギルとオオクチバスの個体数の割合が3.9%，4.5%，16.2%，68.9%，および78.1%と急増した．この優占種の置き換わりにより，市場価格を参考にした生産高変化法によって算出された経済損失額も調査期間中に増加した．これらの結果は，優占種の減少がブルーギルとオオクチバスの増加と同調して起こることと，優占種の減少が潜在的経済損失をもたらすことを示している．生物多様性の回復のためにこれらの2種の侵略的外来種を除去する必要性とその方法についてもあわせて議論した．

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Emergent plant zones on the shores of temperate lakes and ponds function as an essential habitat for various fish species, although few studies have focused on spatial variations in fish fauna over a range of such habitat within a single river system. In order to promote a better understanding of conservation requirements for the fish habitat, the fish fauna of emergent plant zones was investigated by quantitative fyke-net sampling, with measurements of environmental properties, at 19 sites in seven lakes and three ponds in the lower Tone River system, eastern Japan in June and August 2017. A total of 27 and 34 species, including commercially important and threatened species, were collected in June and August, respectively. A cluster analysis based on species composition at each site in each month showed that the fish assemblage was divided into three groups: six medium and large-sized lakes, a small lake and pond on the floodplain, and ponds in the hilly areas. The differences in species composition among the groups were partly related to different elevation, impacts of downstream weirs, and occurrence of introduced piscivorous species. In addition, analyses of the relationships between fyke net catches of eight abundant fishes and environmental variables at each site in the medium and large lakes at lower elevation (< 5 m) in each month, using a generalized linear mixed model, indicated that wave height and mud content in sediments, as well as emergent vegetation size, were significant determinants of abundance of most species. Accordingly, deliberate conservation and rehabilitation of emergent plant zones, taking such essential information into consideration, should be included in future conservation plans for fish habitats in the Tone River system.

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The system for supporting nature-oriented river work was developed for administrative agencies to perceive the distribution of fish species and necessary considerations to conserve or to recreate its habitat in advance to construction works such as river improvements. Distribution maps for 40 fish species, which include primary freshwater fish inhabit the Chikugo and the Onga River systems together with ayu (Plecoglossus altivelis) and Japanese eel (Anguilla japonica), were developed by constructing distribution models for each species by logistic regression analysis based on known habitats and environmental variables such as landscape and land use. Furthermore, options of environmental consideration in construction works for the habitat conservations or recreations were organized in charts. Those outcomes are applied to the Web-based GIS system based on the GSI maps (issued by the Geospatial Information Authority of Japan) which could be browsed with simple operation.

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The brackish and lower reaches of the river are characterized by low flow velocity and large water depth. When environmental DNA metabarcoding surveys in these water area are carried out, it is predicted that DNA substances present in water are distributed in specific points due to settlement, advection and diffusion. Therefore, it may not be possible to accurately grasp the local aquatic biota by collecting water from the surface. In this study, water was collected by longitudinal, transversal and vertical direction in the lower reaches of the Tone River.

As a result, in the case of environmental DNA metabarcoding surveys in brackish and lower reaches of the river, it is thought that fish fauna can be efficiently identified by collecting 2 samples at the possible lower layer in the vertical direction near the riverbank in the survey area.

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コウノトリの採餌環境として着目されている田中調節池において，魚類を対象とした生息状況調査を 2018 年および 2019 年に実施した．また，台風 19 号通過に伴う洪水前後での魚類の分布状況を比較することで，平水時の田中調節池における魚類の生息地としての問題点および今後の配慮方針について検討した．平水時の農閑期（2018 年 12 月）では，支線排水路における魚類の分類群数および個体数は少なく，魚類の全く採集されない調査区も存在した．また，同時期に幹線排水路で確認された魚類が末端排水路ではほとんど記録されなかった．洪水後の農閑期（2019 年 11 月～12 月）には，支線排水路において魚類の分類群数，個体数ともに洪水前に比べて顕著に増加し，洪水前にはみられなかったタモロコやメダカ属等が採集された．また，洪水前には乾燥していた支線排水路も洪水後には湛水され，ドジョウ等の魚類が採集された．洪水後の各支線排水路におけるドジョウの個体数や魚類全体の個体数および分類群数には泥深が正の効果を示し，底泥の柔らかい水路環境が魚類の越冬環境として好適と考えられた．2019 年の農繁期における水田調査では，カラドジョウの繁殖のみが田面で確認された．以上より，洪水によって利根川本川から幹線排水路，支線排水路まで水域が連続し，魚類の分布域が拡大することが示唆された．その一方で，平水時の支線排水路までの連続性は低く，農繁期に多種の魚類が田面まで遡上できないこと，農閑期には支線排水路で魚類が十分に越冬できないことが明らかになった．平水時の田中調節池における魚類の繁殖場所・越冬場所としての機能を高めるためには，特に幹線排水路と支線排水路，そして支線排水路と田面との落差を解消させること，さらに底泥の柔らかい水路区間を積極的に保全し，河道内のワンド等とも連続させることで魚類の越冬場所を確保することが重要と考えられた．その一方で，こうした取り組みによって外来種の分布域を拡大させる可能性があることにも留意し，健全な水域の連続性の確保を目指す必要があるだろう．

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河川の人工護岸・直線化は河川内の生物多様性を減少させる要因の一つである．近年，生物多様性保全に配慮した多自然川づくりの一環として，人工護岸の撤去や河道の拡幅が，各地で実施されつつある．このような多自然川づくりが行われた河川と行われていない河川の水生動物群集を比較する事は，河川改修の生態系への評価を行う上で欠かせない．本研究では，千葉県内の同じ水系に属し，隣接する河川である駒込川（都市型の河川）と，木戸川（多自然川づくりを施行）の水生動物相を比較することで多自然川づくりに基づく河川改修によって，水生動物の分類群数や物理環境の特徴に差があるかどうかを評価した．結果は，木戸川の方が生物種数（分類群数），個体数密度ともに高く，調査地点間の種組成の相違も大きいことが分かった．また，河川内の流速や水深などの物理環境は，駒込川と比べて木戸川では多様であることが分かった．以上のことから，木戸川で実施された多自然川づくりによる河川改修は生物のハビタットとなる環境の創造や，水生動物の多様性保全に寄与したと考えられる．

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We focused on flood channel excavation that forms a gently sloping surface for preventing redeposition of soil and investigated a flood channel that has passed more than 2 years after the excavation to evaluate the riparian area’s function as habitat of floodplain-dependent species (plants, fishes) in the Kikuchi river.

As a result, floodplain dependent species were found due to be created an area its relative elevation from ordinary water level is low and an intricate river side. It was found from the result that the excavation had a good influence on creating habitats of floodplain dependent species and the stumpig contributes to create the fluvial lagoon. However it was suggested that exclusion of an alien species must also be considered in addition to conservation of floodplain dependent species because some alien species invaded and became established.

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The restoration of river ecosystems is of worldwide interest. Although various techniques have been designed, an effective method for environmental evaluation is necessary. We report a new method for the evaluation of the riverine environment on the basis of simple fish ecological data. The 16 indexes studied were (1) native species, (2) alien species, (3) red list species, (4) genuine freshwater fish species, (5) amphidromous or brackish water fish species, (6) swimming species, (7) benthonic species, (8) flowing water species, (9) still water species, (10) permanent water species, (11) temporary water (flood plain) species, (12) spawning in vegetation area species, (13) spawning in muddy bottom species, (14) spawning in sandy-gravely bottom species, (15) spawning under rocks species, and (16) spawning in mussel species. The reference data is the maximum number of potential species . First, the fish fauna data of the evaluated point was obtained. Next, a radar chart was prepared with regard to the 16 indexes. Although this assessment method can be applied in the same ecoregion, it provided a good evaluation.

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