Ichthyological Research

, Volume 57, Issue 1, pp 78–84 | Cite as

Present status and conservation of the markless forms of stream-resident masu salmon Oncorhynchus masou (the so-called ‘iwame’) in Japanese mountain streams

  • Yuichi KanoEmail author
  • Takuya Kondou
  • Yoshitaka Shimizu
Full Paper


As a markless form of stream-resident masu salmon (Oncorhynchus masou), the so-called ‘iwame,’ which can be distinguished from the sympatric normal form of the salmon by their plain body pattern, has been previously reported among seven local populations (A–G) in Japanese mountain streams. In the present study, all populations but B (where any information is entirely missing) were surveyed in a snorkeling survey (detection rate: 34.7%) in 2005 to elucidate the recent conditions of the markless forms. The ratios of the markless forms were 13.0% (9/69), 0.0% (0/364), 5.6% (68/1,205), 0.8% (1/132), 0.0% (0/1,181) and 64.6% (155/240) in A, C, D, E, F and G, respectively. Markless forms might indeed be already extinct in C and F where the stocking of non-native hatchery individuals has been carried out extensively. The same survey was repeated in D in 2009: the markless ratio had significantly decreased to 2.4% (19/783), although the reason for this was unknown. In D, the ratio of the markless form was higher in the mainstream as opposed to the tributaries in both 2005 and 2009, which might imply that the habitat of the markless form differs from that of the normal form.


Color mutant Fish stocking Genetic disturbance Intraspecific diversity Oncorhynchus iwame 



We thank Y. Harada, T. Ikada, O. Inaba, S. Kan, T. Kawasaki, T. Kikkou, E. Kimura, S. Kimura, J. Kitajima, J. Kitamura, K. Kondou, M. Kuwabara, H. Miwa, M. Mori, S. Mori, K. Okada, T. Okayama, Y. Saito, Y. Sakakura, T. Sato and Y. Tomida for valuable information and support in the field. We also thank Choshi River Fisheries Cooperative Association, Kami-ishidu Local Resource Center, Makita River Fisheries Cooperative Association, Ohsugi-dani Nature School, Omogo Mountain Museum, Omogo-gawa Fisheries Cooperative Association, Ôno-gawa Fisheries Cooperative Association and the So-in Fisheries Cooperative Association for helpful information and photograph permission. This research was partially supported by a Ministry of Education, Culture, Sports, Science and Technology Grant-in-Aid for JSPS Fellows, DC2, 2004, 09581 to Y.K.


  1. Dizon AE, Lockyer C, Perrin WF, Demaster DP, Sisson J (1992) Rethinking the stock concept—a phylogeographic approach. Conserv Biol 6:24–36CrossRefGoogle Scholar
  2. Donnelly WA, Dill LM (1984) Evidence for crypsis in coho salmon Oncorhynchus kisutch (Walbaum), parr: substrate colour preference and achromatic reflectance. J Fish Biol 25:183–195CrossRefGoogle Scholar
  3. Dunham JB, Vinyard GL, Rieman BE (1997) Habitat fragmentation and extinction risk of Lahontan cutthroat trout. N Am J Fish Manage 17:1126–1133CrossRefGoogle Scholar
  4. Elser AA (1968) Fish populations of a trout stream in relation to major habitat zones and channel alterations. Trans Am Fish Soc 97:389–397CrossRefGoogle Scholar
  5. Ford MJ (2002) Selection in captivity during supportive breeding may reduce fitness in the wild. Conserv Biol 16:815–825CrossRefGoogle Scholar
  6. Freshwater Fish Protection Association (1981) The 10th business report of Freshwater Fish Protection Association. Tansuigyo (7):173–180Google Scholar
  7. Gamborg C, Sandøe P (2004) Beaver and biodiversity: the ethics of ecological restoration. In: Oksanen M, Pietarinen J (eds) Philosophy and biodiversity. Cambridge University Press, Cambridge, pp 217–236CrossRefGoogle Scholar
  8. Gunderson DR (1993) Surveys of fisheries resources. Wiley, New YorkGoogle Scholar
  9. Hayashi S, Tsuchiya S, Kondo K, Shibano H, Numamoto S, Kosugi K, Yamakoshi T, Ikeda A (2004) Sediment related disasters caused by typhoon Meari (T 0421) in Miyagawa village, Mie Prefecture on September 29, 2004 (prompt report). Jpn Soc Erosion Control Eng 57:48–55Google Scholar
  10. Hidaka T (1979) Evolutional significance of the parr mark. Tansuigyo (5):55–59Google Scholar
  11. Ida T, Okamoto S, Okawa M, Sato Y (1981) About markless form of masu salmon. Fish Genet Breed Sci 6:34–36Google Scholar
  12. Inaba O (1998) Fish fauna in northern coast of Ibaragi Prefecture. Ibaragi Seibutsu 18:1–15Google Scholar
  13. Itô T (1979) Fishes and amphibians of Mt. Ishizuchi and Omogo Valley in the Ishizuchi Quasi-National Park. Rep Nat Conserv Soc Japan 58:99–113Google Scholar
  14. Itô T, Isa J, Yamauchi A (1973) On a rare salmonid fish, Oncorhynchus iwame Kimura et Nakamura, found in a mountain stream of the Omogo River system, Shikoku. Mem Ehime Univ Sci Ser B (Biology) 7:6–12Google Scholar
  15. Jones MW, McParland TL, Hutchings JA (2001) Low genetic variability in lake populations of brook trout (Salvelinus fontinalis): a consequence of exploitation? Conserv Genet 2:245–256CrossRefGoogle Scholar
  16. Kagehira M (2003) A survey on condition of iwame population. Rep Ôita Pref Ocean Fish Resour Cent Inlandwater Proj 13:14–17Google Scholar
  17. Kagehira M, Tokumitsu S (2003) Iwame’s effect of transplant discharge on the upstream from natural living region. Rep Ôita Pref Ocean Fish Resour Cent 4:71–76Google Scholar
  18. Kano Y, Shimizu Y (2007) Threatened fishes of the world: Oncorhynchus iwame (Kimura & Nakamura 1961) (Salmonidae). Environ Biol Fish 78:215–216CrossRefGoogle Scholar
  19. Kano Y, Shimizu Y, Kondou K (2006) Sympatric, simultaneous, and random mating between markless trout (iwame; Oncorhynchus iwame) and red-spotted masu salmon (amago; Oncorhynchus malsou ishikawae). Zool Sci 23:71–77CrossRefPubMedGoogle Scholar
  20. Kato F (1991) Life histories of masu salmon and amago salmon (Oncorhynchus masou and Oncorhynchus rhodurus). In: Groot C, Margolis L (eds) Pacific salmon life histories. UBC Press, Vancouver, pp 447–520Google Scholar
  21. Kimura E (1972) Talking with love the fishes in mountain streams. Tansuigyo Hogo Kyokai, OsakaGoogle Scholar
  22. Kimura S (1989) About iwame. In: Kawanabe H, Mizuno N (eds) Freshwater fishes of Japan. Yama-Kei, Tokyo, p 168Google Scholar
  23. Kimura S, Nakamura M (1961) A new salmonid fish, Oncorhynchus iwame sp. nov. obtained from Kyushu, Japan. Bull Biogeogr Soc Japan 22:69–74Google Scholar
  24. Kondou T, Takeshita N (2005) Ecology of iwame trout—migration, growth and spawning. In: Katano O, Mori S (eds) Current condition and future perspective of rare freshwater fishes—a scenario of positive conservation. Shinzan-Sha, Tokyo, pp 232–239Google Scholar
  25. Madeira MJ, Gómez-Moliner BJ, Barbé AM (2005) Genetic introgression on freshwater fish populations caused by restocking programmes. Biol Invasions 7:117–125CrossRefGoogle Scholar
  26. Maeda N, Hidaka T (1979) Ethological function of the parr marks in a Japanese trout, Oncorhynchus masou f. ishikawai. Zool Mag 88:34–42Google Scholar
  27. Maynard Smith J (1982) Evolution and the theory of games. Cambridge University Press, CambridgeGoogle Scholar
  28. Morán P, Perez J, Dumas J, Beall E, García-Vázquez E (2005) Stocking-related patterns of genetic variation at enzymatic loci in south European Atlantic salmon populations. J Fish Biol 67(Suppl A):185–199CrossRefGoogle Scholar
  29. Mori S, Nagoshi M (1986) Morphological comparisons between the markless masu trout (iwame) and the red-spotted masu trout (amago), Salmo (Oncorhynchus) masou macrostomus GÜNTHER, in the Mikuni-dani Stream of Mie Prefecture, Japan. Bull Fac Fish Mie Univ 13:135–143Google Scholar
  30. Morita K, Yamamoto S (2002) Effects of habitat fragmentation by damming on the persistence of stream-dwelling charr populations. Conserv Biol 16:1318–1323CrossRefGoogle Scholar
  31. Murata G, Koyama H (1976) On the “Sohayaki element” defined by Dr. G. Koidzumi. Mem Nat Sci Mus 9:111–121Google Scholar
  32. Nagoshi M (1981) Oncorhynchus iwame and O. rhodurus found in the Mikuni-dani Stream of Mie Prefecture, Japan. Bull Kansai Org Nat Conserv 7:5–8Google Scholar
  33. Nakamura M (1970a) Oncorhynchus iwame found in eastern Japan. Tsuribito 294:47–49Google Scholar
  34. Nakamura M (1970b) Oncorhynchus iwame found in eastern Japan again. Tsuribito 295:67–69Google Scholar
  35. Nature Conservation Committee of Ichthyological Society of Japan (2009) Guidelines for the fish stocking for biodiversity conservation. Accessed 24 April 2009
  36. Omogo Mountain Museum (1996) Photographs of events and sceneries in the Ishizuchi Mountains. Bull Omogo Mt Mus 5:8Google Scholar
  37. Perrow MR, Côté IM, Evans M (1996) Fish. In: Sutherland WJ (ed) Ecological census techniques. Cambridge University Press, Cambridge, pp 178–204Google Scholar
  38. Peters JC, Alvord W (1964) Man-made channel alterations in thirteen Montana streams and rivers. Trans N Am Wildl Nat Res Conf 29:93–102Google Scholar
  39. Ryder OA (1986) Species conservation and systematics: the dilemma of subspecies. Trends Ecol Evol 1:9–10CrossRefGoogle Scholar
  40. Sato S (1998) The native trout anthology. Turibito-Sha, TokyoGoogle Scholar
  41. Sato T, Watanabe K (2004) Spawning site characteristics of Kirikuchi charr Salvelinus leucomaenis japonicus: southernmost population, and effect of angling pressure. Jpn J Ichthyol 51:51–59Google Scholar
  42. Shimizu Y, Katayama T, Kada K (2005) Investigation report of iwame and other species in the Mikuni-dani Stream. Mie-Ken, TsuGoogle Scholar
  43. Shiraishi K (1993) The faces of Japanese white-spotted charr. Yama-Kei, TokyoGoogle Scholar
  44. UNCED (2009) Convention on biological diversity. Accessed 22 April 2009
  45. Waples RS (1991) Genetic interactions between hatchery and wild salmonids: lessons from Pacific Northwest. Can J Fish Aquat Sci 48(Suppl 1):124–133Google Scholar
  46. Waples RS (1995) Evolutionarily significant units and the conservation of biological diversity under the endangered species act. Am Fish Soc Symp 17:8–27Google Scholar
  47. Yamauchi A (1982) The results of artificial incubation of iwame and iwame–amago crossbreeding experiment. Tansuigyo Extra Vol on Yamame and Amago:119–124Google Scholar

Copyright information

© The Ichthyological Society of Japan 2009

Authors and Affiliations

  • Yuichi Kano
    • 1
    • 4
    Email author
  • Takuya Kondou
    • 2
  • Yoshitaka Shimizu
    • 3
  1. 1.Department of BioresourcesGraduate School of Mie UniversityTsuJapan
  2. 2.West Japan Freshwater Fishes Research GroupKikuchiJapan
  3. 3.The Inabe River Nature Research GroupInabeJapan
  4. 4.Department of Urban and Environmental EngineeringKyushu UniversityNishi-kuJapan

Personalised recommendations