〔 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.