〔 水 産 増 殖45巻4号497-503 SUISANZOSHOKU (1997-H9),〕

Geographical Distributions of Two Bagrid Catfishes in

Kyushu, Japan

Shinji MIZOIRI1), Naohiko TAKESHITA2), Seirð¯ KIMURA3),

and Osame TABETA1)

1) Graduate School of Marine Science and Engineering , Nagasaki University, Bunkyo, Nagasaki, Nagasaki 852-8131, Japan 2) D epartment of Applied Aquabiology, National Fisheries University, Nagata-hon, Shimonoseki, Yamaguchi 759-6533, Japan 3) Kashii , Fukuoka, Fukuoka 813-0011, Japan

Abstract Two Bagrid catfishes, Pseudobagrus aurantiacus and P. nudiceps are found in Kyushu, Japan. This paper reports a survey made to elucidate the exact range of each species, and to grasp the present habitation status of P, aurantiacus. The survey was made by field fishing trips , interviewing fishermen, and sending questionnaire to the cooperative fishery associations of each reach . The result showed that P. aurantiacus was inhabiting 14 river systems in the whole western side of the island, while P. nudiceps was inhabiting 11 river systems in northeastern Kyushu facing to the Seto Inland Sea, and in the Kuma River, southwestern Kyushu where it might be introduced artificially from Lake Biwa. P. aurantiacus tends to increase in parts of some river systems, but its distributional range in the most river systems is still restricted to small area.

Four species of bagrid catfishes (Siluriformes) are Kikuchi R., Kuma R., Midori R., Mifune R., Tsuetate R. found in Japan1-3). One of them, Pseudobagrus auras (Kumamoto Pref.), Oyodo R. (Miyazaki Pref.), Hiwa- tiacus (Fig. 1-a) confined to Kyushu1-7), is consid- tashi R., Sendai R., and Kotsuki R. (Kagoshima ered decreasing in population drastically and being Pref.) 2,5,9-14). But the current distributional range of threatened by such environmental deterioration as riv- the fish was unclear. Knowing their exact range is er improvement and water pollution8). The Japanese essential for conserving the fish.

Environmental Agency has designated this small cat- P. nudiceps (Fig. 1-b) is widely distributed through- fish as an•gEndangered Species•hin 19918). So far, P. out western Honshu, a part of Shikoku and northeast- aurantiacus has been recorded in the following rivers: ern Kyushu1,4-7), but the southwest extreme of its Yabe River, Chikugo R. (Fukuoka Fref.), Chikugo R., distribution was poorly known until now. P. nudiceps Shirohara R., Tabuse R., Naka R., Hama R., Tara R., is considered to extend its distributional area year by Matsuura R., Arita R. (Saga Fref.), Sakai R., Nagata R., year15-17).It is necessary to know whether the fish has Honmyo R., Iki Island (Nagasaki Pref.), Tsuboi R., encroached on the new location.

Received:August 4, 1997 Key words:Pseudobagrus aurantiacus, Pseudobagrus nudiceps, Freshwater fish, Conservation biology 498 S. Mizoiri et al. (1997)

Fig. 1. Pseudobagrus aurantiacus collected from the Hiwatashi R. of Sendai R. syst., Kagoshima Prefecture, 119.3mm SL (a); Pseudobagrus nudiceps from Yakivama R. of Onga R. svst., Fukuoka Prefecture, 106.0 mm SL (b). Both species are clearly distinguishable each other based on the shape of caudal fin. Scales indicate 50 mm.

We have surveved the occurrence of both species scoop nets. The specimens were preserved in a 10% in each river system of Kyushu since 1990. Here, we buffered formalin at the collecting points, and their report the geographical distributions and living standard length was measured in our laboratory. All environment of the two bagrid catfishes in Kyushu. the specimens used in this study were deposited in the Japan. Department of Applied Aquabiologv. National Fisher- ies University, Shimonoseki, Japan. In addition, we Methods talked with fishermen at each place, and sent question-

Field surveys were carried out at 14 reaches in naires to the cooperative fishery associations at each

Fukuoka Pref., 9 reaches in Saga Pref., 15 reaches in river, adding the explanation about the difference of

Nagasaki Pref., 15 reaches in Oita Pref., 7 reaches in audal fin shape of both fishes as discernible character

Kumamoto Pref., 10 reaches in Mivazaki Pref., and 7 reaches in Kagoshima Pref., from April 1990 to Results September 1996. Field surveys were carried out main ly from April to October, when ecological activities of Disirihution of Pseurlobagrus aurautiacus

PR aurautiacus were high. P. aurautiacus was collected from 17 reaches of 11 Hook and line and gill nets were mainly used in river systems. From questionnaire replies it occurs in deep water, and cast nets were adopted in shallows to 10 reaches (Fig. 2. Table 1). According to Dr. Shino- catch the fish swimming and feeding actively at night. miya. the fish was also found in the Maesato River of

During the clay, bagrids hiding under the vegetated the tofu River system adjoining to the Antori River river bank of the shallows and rapids were caught by system, Kagoshima Prcf*.

* Personal communication , Prof. Shinomiva, Faculty of Fisheries, Kagoshima University, conducted the research in 1993. Geographical distributions of bagrid catfishes

P. aurantiacus appeared in small tributaries and in

the downstreams as well. They were found mostly in the rapids with pebble and boulders in the bottom

along dense vegetated bank at the upper-side of

depths, or shallow.

Distribution of Pseudobagrus nudiceps P. nudiceps was collected from 6 reaches of 5 river systems and from questionnaire replies it occurs in 7 river systems. Distributional areas of this species appeared to be limited into northeastern Kyushu facing to the Seto Inland Sea and the Kuma River, southwest- ern Kyushu (Fig. 2, Table 1). P. nudiceps was not found coexist with P, aurantiacus, except in the Kuma River. P. nudiceps appeared mostly in the depths or slug gish areas with rocky or bouldery bottom. Habitats of P. aurantiacus and P. nudiceps resemble each other, but P, nudiceps seems to prefer slower current than P. au

Fig. 2. Distributions of P. aurantiacus and P. nudiceps rantiacus does. Sometimes the fish occurred in brackish

in Kyushu, Japan. •£ and •¢ indicate for the water.

localities of P. aurantiacus; •œ and •› indicate

for the localities of P. nudiceps; solid symbols Discussion

were confirmed by collecting; open symbols were Habitation status of P. aurantiacus based on the questionnaires. 1. Ohno River P. aurantiacus was found in the most part of the (Ohno River syst.); 2. Nanase R. (Oita R. syst.); localities ever known, however, the local habitats of 3. Yorimo R. (Yorimo R. syst.); 4. Yakkan R. the fish in the most reaches were supposed to shrink. (Yakkan R, syst.); 5. Iroha R. (Iroha R. syst.); 6. Inumaru R. (Inumaru R. syst.); 7, 8. Yamautsuri Though we could not confirm the occurrences of P. au

R., Yamakuni R. (Yamakuni R. syst.); 9. Sai R. rantiacus in the Kuma River, Kumamoto Pref. and the (Sai R. syst.); 10. Iwatake R. (Iwatake R. syst.); Kotsuki River, Kagoshima Pref., in this study, it was 11. Ima R. (Ima R. syst.); 12. Yakiyama R. (Onga reported that the fish had occurred in these river sys- R. syst.); 13. Naka R. (Naka R. syst.); 14, 15, 16. tems in the past10,11,18). According to questionnaire Matsuura R., Ikisa R., Kyuragi R. (Matsuura R. replies, P. aurantiacus seemed to distribute around the syst.); 17. Kori R. (Kori R. syst.); 18. Kawatana

R. (Kawatana R. syst.); 19, 20. Honmyo R., Naga- Oyodo River system including such reaches as the

ta R. (Honmyo R. syst.); 21. Sakai R. (Sakai R. Shou, Mina, Shounai, Hagiwara, or Aya River 20-30 syst.); 22, 23. Naka R., Shiota R. (Shiota R. years ago, however, it was found only in the Ura- syst.); 24, 25, 26, 27. Koishiwara R., Chikugo R., nomyo River, a small tributary of the Oyodo River sys- Ono R., Mikuma R. (Chikugo R syst.); 28. Yabe tem in the present study (Fig. 2-41). The fish seemed R. (Yabe R. syst.); 29. Iwano R. (Kikuchi R. to distribute around the Amori River system as well as syst.); 30, 31, 32, 33, 34. Akai R., Mifune R., the Oyodo River system, 20-30 years ago, while there Tsutsu R., Midori R., Shakain R. (Midori R. was no report on habitat of P. aurantiacus. Local syst.); 35. Kuma R. (Kuma R. syst.); 36, 37, 38,

39. Hiwatashi R., Maesendai R., Ana R., Kubuki fishermen's answers to the questionnaires stated that

R. (Sendai R. syst.); 40. Amori R. (Amori R. the fish still lives in the upper reaches of the river

syst.) 41. Uranomyo R. (Oyodo R. syst.). system (Fig. 2-40), but it has not been confirmed. The Dverall conclusion from questionnaire replies and from 500 S. Mizoiri et al. (1997)

Table 1. List of distributions of Pseudobagrus aurantiacus and Pseudobagrus nudiceps

Pa: Pseudobagrus aurantiacus, Pn: Pseudobagrus nudiceps, C: collecting, Q: questionnaire. *Periodic sampling site for survey of population structure , dynamics, etc. talking with fishermen were that until 20-30 years On the contrary, the numbers of P, aurantiacus in ago, distributional range of the fish appeared wider certain areas of Matsuura, Chikugo, and Yabe River (e. g., small tributaries or irrigational canals) than system seem to recover in recent years, for the fisher- recent range. P. aurantiacus seems to have been a men said that sometimes they captured more P. auran- common species in the most reaches in Kyushu until tiacus than Plecoglossus altivelis altivelis by gill net re- about 20 years ago, and the decline of the fish seems to cently, though P, aurantiacus had been hardly captured have occurred simultaneously in each reach. in these reaches in early 1970's. We also discovered Geographical distributions of bagrid catfishes 501

that the fish was abundant in these river systems and and Sarcocheilichthys variegatus microoculus have colo- the Sendai River system, Kagoshima Pref. nized in the Kuma River11,18). The typical habitat for P. aurantiacus well accords P. aurantiacus did not occur in the distributional with so-called Aa-Bb transitional type, or Bb type de- area of P. nudiceps in northeastern Kyushu, and the fined by Kani for middle reaches in river19). The habi- distributional patterns of both fishes were considered tats of the fish seem isolated into those areas in each to be allopatric completely, but the related Liobagrus reach, and overall distribution still appears to be re- reinii extends its distribution into P. nudiceps's stricted now. It might be resulted from intercepting the area6.21). remigration and dispersal of the fish by river improve- This implies the presence of competition between ments such as dam construction or dredge of river bed. the two fishes. It is thought that Japanese bagrid cat- Further observation is necessary to understand the ex- fishes speciated from the different continental ances- act inhabiting situation of in each river system. tors and entered into the Japanese Archipelago independently22).It is considered that P. nudiceps Natural distribution and artificial introduction of P. entered from continent into the Japanese Archipelago nudiceps in early Pliocene at latest, and P. aurantiacus The populations of P. nudiceps distributed in north- entered more recently than other Japanese bagrid eastern Kyushu along the Seto Inland Sea, seemed to catfishes2,22).If this is true, the range of P, auran- be a native, as the fish was found continuously in the tiacus may have been limited by being excluded from region in spite of the river scale. Sakaizumi dissected the areas already colonizedby P. nudiceps. the genetic variation of Oryzias latipes among regional In recent years P. nudicepsdevelops new localities in populations, showed the regional variation of these Honshul5-17).They should be studied from the view small fishes well reflecting the large river system point of population genetics to identify their origin. formed during the glacial age of the Pleistocene by re- Suppose that P. nudicepsis introduced into the distri- gression of the Seto Inland Sea, and the killifishes in- butional area of P. aurantiacus, the former fish may habiting in northeastern Kyushu was the same group affect the survival of the latter fish, as the new comer to the populations of southwestern Honshu20). These often causes the extinction of the native species23-25). results suggest that freshwater fish is able to immi- We must abstain from indiscreet introduction of fish grate between northern Kyushu and southwestern Hon- species into new location. shu through this old freshwater system, and appear to Acknowledgment support the speculation that P. nudiceps distributing in northeastern Kyushu is a native. We extend our particular appreciation to Dr. Gordon On the other hand, it is thought that P. nudiceps R. Williamson for the critical reading of manuscript, found discontinuously in the Kuma River was artifi- and Prof. A. Shinomiya (Faculty of Fisheries, Kagoshi- cially introduced with P. altivelis altivelis from Lake ma University), Prof. S. Matsui, Mr. S. Nagata, Mr. E. Biwa, middle Honshu, Japan, by following reasons: so Miyamura, Mr. N. Onikura (Faculty of Agriculture, far any reaches where Japanese bagrid catfishes Kyushu University), and Mr. Y. Nakagawa (Kobayashi distributed sympatrically, have never been known. The Branch, Miyazaki Prefectural Fisheries Experimental Kuma River has been reported as the native habitat of Station) for supplying with us valuable information P. aurantiacus11,18). P. nudiceps was confirmed for the about habitat of P. aurantiacus. We also extend our first time in the Kuma River in 1985 by the research of thanks to everyone of Freshwater Laboratory, Environment Agency18). According to the fishermen of Fukuoka Fisheries and Marine Technology Research the Kuma River, P. nudiceps began to establish in the Center for accommodatingus to reserve and measure Kuma River around 1990. Endemic species to Lake specimens. Biwa such as Acheilognathus cyanostigma, Squalidus chankaensis biwae, Opsariichthys uncirostris uncirostris, 502 S. Mizoiri et al. (1997)

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九 州 におけるギギ科魚類2種 の地理的分布

溝 入 真 治1)・ 竹 下 直 彦2)・ 木 村 清 朗3)・ 多 部 田 修1) (1)長崎 大 学 大 学 院 海 洋 生 産 科 学研 究科,2)水 産 大 学 校 生 物 生 産 学 科,3)福 岡市 香 椎4-2-24)

九 州 に は ア リ ア ケ ギ バ チPseudobagyus auyantiacusと ギ ギP.nudicepsの2種 の ギ ギ 科 魚 類 が 生 息 す る こ とが 知 られ て い る。 これ ら2種 の ギ ギ科 魚類 の 九州 に お け る正 確 な分 布 を明 らか に し,ア リ アケ ギ バ チ の現 在 の 生 存 状 況 を把握 す るた め,各 河 川 で採 集,聞 き取 りお よ び ア ン ケ ー ト調 査 を行 った 。 そ の結 果,ア リ ア ケギ バ チ は14水 系27河 川 に生 息 を認 め た。 ギ ギ は九 州 北 東 部 の 瀬 戸 内 海 に面 す る11水 系 に 連 続 分 布 し,さ ら に球 磨 川 に不 連 続 分布 す る こ と(人 為 移 入 と思 わ れ る)を 確 認 した。 一 部 の 河 川 の 限 ら れ た流 域 で は ア リ アケ ギ バ チ の個 体 数 は増 加 傾 向 に あ るが,各 水 系 内 の 流 程 分 布 は依 然,局 所 的 で あ る と考 え られ た 。