The distributions of five species of freshwater goby, Rhinogobius spp.(Rhinogobius sp.CB, OR, LD, DA and CO, according to recent morphological definitions) and R. fiumineus were surveyed at 264 points in 114 streams and rivers on the coastal area of Ise Bay, Japan. Rhinogobius sp.CB (cross-band type) was found in most of the rivers investigated, with R. sp.OR (orange type) occurring in many rivers on the Atsumi and Chita Peninsulas. The possibility of separate origins for the latter populations was discussed. Rhinogobius sp.LD (large-dark type) was found longer rivers flowing across the plains. Rhinogobius sp.DA (dark type) inhabited only a few rivers on the Shima Peninsula. In those rivers habitat segregation was observed between the former and R. flumineus. Rhinogobius sp.CO (cobalt type) occurred in rivers on the Kii Peninsula.

抄録全体を表示

Members of the genus Rhinogobius are widely distributed in Far East Asia, at least 11 species having been recognized in Japan. Of the six species recorded from Okinawa Island, two are land-locked (“aobara-yoshinobori” R. sp.BB and “kibara-yoshinobori” R. sp.YB) and the remainder amphidromous. Embryonic development and morphological changes in the two land-locked species are described from artifically-reared eggs, larvae and juveniles. Survival and growth of the two species were compared under different salinities (0-35%0) dur-ing a 21-day period following hatching. Although egg diameters of both species were almost the same (“aobara-yoshinobori”; 4.3±0.1 mm, “kibara-yoshinobori”; 4.3±0.2 mm), newly-hatched larval morphology, and larval and juvenile salinity tolerance clearly differed. Newly-hatched larvae of “aobara-yoshinobori” had a flexed notochord and caudal fin rays already developed. The yolk was completely consumed 3 days after hatching. By comparison, “kibara-yoshinobori” hatched at an ealier developmental stage, having a straight notochord. The yolk disappeared 7 days after hatching. Larvae and juveniles of “aobara-yoshinobori” were less toler-ant in high salinity than those of “kibara-yoshinobori”. The results suggested that the two land-locked gobies have become adapted to a wholly fluvial life cycle, through somewhat different strategies.

抄録全体を表示

The genus Rhinogobius is widely distributed across Japan and East Asia, including Japan, comprises amphidromous, fluvial, lacustrine, and land -locked species. Because R. kurodai (Tanaka 1808) an endemic species formerly known as Rhinogobius sp. OR (Tou–yoshinobori species complex), in the Kanto region, central Japan, but recently re –assessed taxonomically, has been less studied from ecological, taxonomic and genetic perspectives than other Rhinogobius species, this study investigated ontogenetic morphological changes in artificially –reared larvae and juveniles of the former, in addition to larval salinity tolerance. Larval salinity tolerance is described for artificially -reared newly -hatched larvae reared in eight tanks (0, 5, 10, 15, 20, 25, 30, and 35 psu). Newly -hatched R. kurodai larvae (3.2 ± 0.1 mm in notochord length) had one or two symmetrical pairs of cupulae, (free neuromast organs), on the trunk around the anus or tail region, such having been previously reported in the genus only from larvae of R. sp. BF, a lacustrine species Nine days after hatching (4.5 mm in standard length: SL), the notochord tip projected upwards, and the second dorsal and anal fin ray were formed. Between eighteen (5.6 mm SL) to twenty-one days (6.4 mm SL), the larvae settled to the bottom of the aquarium tank. At thirty-five days (11.2 mm SL), all fins and scales were formed (juvenile stage). All larvae subjected to salinities of 20 to 35 psu died within three days, evidence (together with than of small sized-eggs and ealy presence of larval cupulae) suggesting that R.kurodai is a lacustrine -type species.

抄録全体を表示

河川人工構造物は，水生生物個体群の分断化を引き起こす．本研究では，貯水ダムが設置されている愛媛県の加茂川と中山川において類の遺伝的集団構造の解析および回遊履歴の判定を行い，ダムによる分断の程度を評価することを目的とした．加茂川および中山川の 6 地点からシマ，オオ，トウ，カワを 20～39 個体採集し，各個体の胸鰭から DNA を抽出した．マイクロサテライト領域の増幅には Rhi-5^*, -7^*, -11^* の3 種のマーカー座を用い，アリルサイズを決定し遺伝的解析に用いた．耳石による回遊履歴の判定は加茂川の黒瀬ダム上流域の中奥，黒瀬ダム下流域の大久保，中山川下流域の大頭堰からそれぞれシマを 1 から 2 個体の耳石を採取し，Sr/Ca 濃度を測定した．遺伝的多様性を示すヘテロ接合体率 (期待値) の平均値は，シマ (0. 900～0. 921) で最も高く，続いてオオ (0. 869, 0. 889)，トウ (0. 7779 の順となり，カワ (0. 192～0. 271) で最も低く，種により遺伝的多様度に違いが見られた．各個体群間の遺伝的分化を示す異質性検定では，種間で有意差が見られた．耳石 Sr/Ca 解析により，加茂川の黒瀬ダム上流のシマ個体群の陸封化が確認されたが，遺伝的異質性検定では，黒瀬ダムの上流域と下流域のシマ個体群において有意な差は見られなかった．また，中山川のカワでも中山川逆調整池堰堤の上流域と下流域の個体群において有意な差が見られなかった．

抄録全体を表示

河川人工構造物は，水生生物個体群の分断化を引き起こす．本研究では，複数の貯水ダムが設置されている吉野川においてオオの遺伝的集団構造の解析および回遊履歴の判定を行い，ダムによる分断の程度を評価することを目的とした．吉野川の大橋ダム上流および下流の 6 地点からオオを 31～50 個体採集し，各個体の胸鰭から DNA を抽出した．マイクロサテライト領域の増幅には Rhi－5^＊，－7^＊，－11^＊ の 3 種のマーカー座を用い，アリルサイズを決定し遺伝的解析に用いた．耳石による回遊履歴の判定は吉野川下流域から支流の鮎喰川，穴吹川，貞光川，上流域から大橋ダム上流の長沢，長沢ダム上流の越裏門，大森川ダム上流の奥南からそれぞれオオを 1 から 3 個体の耳石を採取し，Sr/Ca 濃度を測定した．遺伝的多様性を示す有効アリル数の平均値は，鮎喰川および貞光川で最も高く（15. 7，15. 9），ダム上流域の個体群で低かった（10. 9～13. 0）．一方，ヘテロ接合体率（期待値）の平均値は竹野川（0. 788）を除きダム上流域と下流域で同等の値を示した（0. 870～0. 890）．遺伝的異質性検定では，大橋ダムの上流域と下流域の個体群間において有意な差が見られた．耳石Sr/Ca 解析により，大橋ダム上流の個体群のダムによる陸封化が確認された一方，貯水ダムの存在しない鮎喰川，貞光川の個体において降海していない個体が確認された

抄録全体を表示

Spawning ground distributions of four amphidromous gobies (Rhino-gobius giurinus, R. sp.CB, R. sp.CO and R. sp.LD) were investigated in the Aizu River, Wakayama Prefecture, Japan. Twenty eight egg clusters of R. giurinus were found in the lower reaches, being deposited mainly in summer. Forty six egg clusters of R. sp.CB were found over a wide distribution range, from lower to middle reaches, nine egg clusters of R. sp.CO in a narrow range, from middle to upstream reaches, and twenty nine egg clusters of R. sp.LD in upstream reaches. Rhinogobius sp.CB, CO and LD deposited eggs mainly in spring. For all four species, spawning ground distributions were in close agreement with those of the adults. Apparently, the differences in spawning ground distribution and spawning season reduce interspecific competition for nest sites and enhance reproductive isolation. The former difference may cause the difference in other reproductive characters such as egg size among four species, because of a negative correlation between the survival of embryos during migrating to the sea and the distance from spawning ground to river mouth.

抄録全体を表示

The longitudinal distribution and dietary habits of five and fbur Rhinogobius species were investigated in the Genka River of northern Okinawa Island, Japan. Two sampling points for the assessment of fbod habits, and locations for determining longitudinal distribution (n=13), were identified along the length of the Genka River. Habitat prefbrence was observed to be relatively discreet among the five Rhinogobius species sampled: R. giurinus was distributed from the tidally influenced river reaches to the lower river reaches, R. sp.MO was commonly fbund in the middle river reaches, R. sp.CB was fbund in riffles along the length of the river without the lowest and uppermost stations, R. sp.DA occurred from the middle to the uppermost river reaches, and R. sp .BB was commonly found in pools from the middle to the uppermost reaches of the Genka River. Four Rhinogobius species (MO, CB, DA, BB) were found to feed primarily on Trichoptera, with R. sp.CB and R. sp.BB also observed to feed on terrestrial insects. R. sp.DA observed to feed on molluscs (snails). These findings suggest that the members of Rhinogobius species assayed in the Genka River have become somewhat specialized with respect to habitat (5 species) and food prefbrence (4 species).

抄録全体を表示

Clutch and egg size in the Japanese amphidromous goby, Rhinogobius sp.DA (R. brunneus, dark type), inhabiting small rivers in the southern part of the Kii peninsula were examined. Clutch sizes, ranging between 1043 and 4436, increased with increasing maternal standard length. Spawned egg volume ranged between 0.85 mm³ and 1.38 mm³, mean egg volumes being similar among the eight rivers sampled during the study. Rhinogobius sp.DA had a relatively larger egg and smaller clutch size compared to those of three other amphidromous Rhinogobius species inhabiting relatively larger rivers in the same region. Inter-specihic egg size variations among the four species appear to result in differing larval survival rates during their migration to the sea.

抄録全体を表示

Larval development and salinity tolerance of Rhinogobius sp. BF are described from artificially-reared eggs, larvae and juveniles. Aquarium-held R. sp. BF spawned small-type eggs (n=816, long axis 1.9 mm, short axis 0.6 mm) on May 17 2004, which were guarded in the nest by a male. Newly-hatched larvae (3.2 mm in notochord length) had a small yolk, and some melanophores apparent on the snout to caudal region. Twenty-two days after hatching (6.8 mm in standard length; SL), the notochord tip projected upwards, and dorsal and anal fin rays appeared. Between thirty (12.0 mm SL) to forty-five days (14.2 mm SL), the larvae settled to the bottom of the aquarium. Sixty days after hatching (15.4 mm SL), all fins and scales were completed (juvenile stage). All larvae subjected to marine salinity (35 psu) died within three days, indicative of the lentic landlocked life history recorded for the species.

抄録全体を表示

The three species of amphidromous gobies (Rhinogobius sp.CB, CO and LD) allopatric in the Aizu River, Wakayama Prefecture, Japan were examined for their clutch size and egg size. Clutch size was the largest in R. sp.CO and the smallest in R. sp.CB, whereas egg size was in the reverse order. Larger clutch size in R. sp.CO and LD than R. sp.CB was partly explained by the difference in body size, because the formar two species have a larger body size at maturation than the latter. The differences in reproductive characteristics may be a result of the different survival rates of larvae during migration to the sea, because their spawning ground distributions are different from one another along the stream.

抄録全体を表示

To clarify the early life history of a fluviatile goby (“Kibara-yoshinobori”) Rhinogobius sp.YB, the morphological characters of newly hatched larva and distribution pattern of larvae were investigated, while collecting the eggs and drifting larvae from March 2000 to April 2002 at four stations in the upper stream of Sumiyo River, Amami-oshima Island, southern Japan. Judging from the appearance of clutch of eggs and larvae, the breeding period was assumed to last for three months from April to June with a peak in May. The egg diameter was larger than that from Okinawa-jima Island and any other waters of Amami-oshima Island. Thelar gest embryos collected from egg clutch showed a postflexion stage, forming second dorsal, anal and principal caudal fin rays. These characters denoted a more advanced stage than previously reported. The larvae gathered in the shallow water area (<40 cm) with low current velocity (<5 cm/s) near shore and around substratum. The swimming ability of the newly hatched larvae and characteristic distribution of the larvae reduced a carry-away risk and thus enabled their life history within stream.

抄録全体を表示

城北ワンド群に生息するトウ縞鰭型について，生息場所スケール(ワンド間比較)と微生息場所スケール(底質型間比較)での分布様式と摂餌生態を調査した．縞鰭型は，本川では採集されず，ワンド内でのみ生息が確認された．とくに，年間を通して小型で底質の小さい閉鎖的なワンドに多く生息していた．微生息場所スケールでは，泥や落葉が多い底質に多く生息していた．充満度(体重に対する消化管内容物湿重量の割合)は5月に高く，とくに，5月の0歳魚で高かった．消化管内容物には，止水環境に生息するケンミジンコ科やシカクミジンコ属などの動物プランクトンや，チビミズムシやユスリカ類などのベントスが多く出現した．これらの結果は，トウ縞鰭型の生活様式が，ワンドの止水環境に適応していることを示している．いっぽう，繁殖期と稚魚期には新設ワンドに多く生息しており，繁殖期の成魚は長径16∼21cmの大きな石の下面に産卵していた．したがって，トウ縞鰭型の生息場所には，餌場としての泥や落葉が堆積した止水域の生息場所と，産卵場としての侵食が卓越した石底のある生息場所が必要なことが示唆された．また，淀川大堰の運用が淀川の環境と類の個体群に与える影響を考察した．

抄録全体を表示

わが国は戦後の拡大造林政策による上流集水域の森林化およびダム建設・河川改修による流況の平滑化が進行している。このようにわが国の戦後の拡大造林政策および治水・利水政策の弊害を検証するためには、上述の期間中の直近 30年程度の中期的な期間のモニタリングが重要になる。本報では、中期的な期間の魚類の個体数変動から河川環境の変化を推定し、望ましい河川整備のあり方を提案することを目的とする。福井県南川に注目し、 2000年から現在に至る河川水辺の国勢調査の結果を解析することによって、魚類相および個体数が豊かな河川における魚類群集の経年変化を統計解析した。南川において、過去約 20年間の魚類調査の結果、カワ

が増加し、ウグイおよびアカザが減少している可能性が示唆された。カワが増加した原因として平瀬が増加し、ウグイおよびアカザが減少した原因として早瀬や淵が減少した可能性が考えられる。今後は、南川において早瀬や淵を造成する河川整備を提案する。

抄録全体を表示

江の川で採集された通し回遊魚（ 3 科 11 種）の耳石 Sr：Ca 比を分析し，回遊履歴を検証した．耳石 Sr：Ca 比のプロファイルより，河口付近で採集されたチチブは，終始，汽水域を主な生息域としていると考えられた．浜原ダムより下流の中流域で採集されたスミウキゴリ，ゴクラクハゼ，シマ，オオ，カマキリ，カジカ中卵型は回遊型と考えられた．ヌマチチブやウキゴリについては中流で採集された個体は回遊型であったが，浜原ダムより上流で採取された個体は非回遊型であった．浜原ダムより上流への回遊型のヌマチチブ，ウキゴリ，シマ，オオの移動は，同ダムの魚道評価の指標となり得る．トウ（宍道湖型）は浜原ダムより下流の個体にも非回遊型が存在することが明らかとなった．ヌマチチブ，ウキゴリ，トウ（宍道湖型）は，回遊パターンに対して柔軟性を有するとことで環境に適応していると考えられた．

抄録全体を表示

Hybrids of Rhinogobius biwaensis and Rhinogobius sp. BF were identified in the ponds of Sento Imperial Palace, Kyoto City, Japan, from microsatellite and mitochondrial DNA markers. Mitochondrial DNA analysis indicated that five of seven Rhinogobius specimens had R. biwaensis haplotypes, the remaining specimens having those of Rhinogobius sp. BF. In DAPC and STRUCTURE analyses based on microsatellite data, all specimens examined showed intermediate status between R. biwaensis and Rhinogobius sp. BF, the two species being considered to have formed a hybrid swarm in the ponds because genetically pure individuals of either were not found. This is the first report of recent hybridization under field conditions in Rhinogobius fishes from Japan, confirmed by nuclear and mitochondrial DNA data. Hybrid Rhinogobius specimens from the ponds had 5–17 predorsal scales, an intermediate range between those of non-hybrid R. biwaensis (0–6) and Rhinogobius sp. BF (11–20). However, in appearance they were more similar to R. biwaensis than Rhinogobius sp. BF, having bluish-white distal coloring anteriorly on the first and second dorsal fins, a reduced reddish longitudinal band on the anal fin, and lacking yellowish dorsal and posterior margins on the caudal fin. However, they differed from R. biwaensis in having a narrower white posterior caudal fin margin. Further morphological differentiation of the hybrid specimens was not apparent.

抄録全体を表示

アラビア湾の北西部の水深5-12mからトロールによって, これまで当海域から報告されていないハゼ科魚類が採集された.本種は孔器や他の外部形質によって, と査定された.の現在の分布を考慮すると, 今回採集された標本はタンカーのバラスト・タンクに入って運ばれたと考えられる.

抄録全体を表示