Title. Author(s)Tamate, T.; Maekawa, K. CitationEurasian Journal of Forest Research, 1: Issue Date Doc URL. Type.

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1 Ttle Lfe cycle of masu salmon (Oncorhynchus masou) n Sh Author(s)Tamate, T.; Maekawa, K. CtatonEurasan Journal of Forest Research, 1: ssue Date Doc URL Type bulletn Fle nformaton 1_P39-42.pdf nstructons for use Hokkado Unversty Collecton of Scholarly and Aca

2 Eurasan J. For. Res. 1: 39-42, 2000 Hokkado Unversty Forests, EJFC Lfe cycle of masu salmon (Oncorhynchus masou) n Shumarna Lake, northern Hokkado, Japan Tamate, r.h and Mae kawa, K. 2 1 Graduate School of Agrculture, Hokkado Unversty, Sapporo , Japan 2 Hokkado Unversty Forests, Sapporo , Japan Abstract We descrbed some lfe-hstory trats of masu salmon (Oncorhynchus masou) n Shumarna Lake, northem Hokkado, Japan. Males occurred both lake-run form and fluval form but all females were lake-run form. Age at maturty of lake-run form was 1+~3+ n males and 2+ and 3+ n females. Males of fluval form (mature male parr) matured at 0+~2+. Mean fork length at maturty of lake-run form was about 280mm n males and about 350mm n females, beng markedly smaller than the sea-run adults. Ths appeared to be due to the low food abundance and the relatvely low water temperature for longer perods n Shumarna Lake. The lfe cycle of masu salmon n Shumarna Lake s smlar to that of the sea-run populatons, whch nclude both the semelparous mgratory type (almost all females and a few males) and the teroparous stream-resdent males. However, two partcular lfe cycles probably exst n Shumarna populatons: juvenle parr mgratng to the lake before smoltfcaton and "Jack" (precocous lake-run males) that do not wnter n the lake after smoltfcaton. These lfe cycles are pecular to lacustrne populatons. Key words: masu salmon, Shumarna Lake, lacustrne populaton, smolts, mature male parr, lake-run adults, juvenle parr, Jack ntroducton Masu salmon (Oncorhynchus masou) dstrbute n far-east Asa, and as wth other salmon ds, have several lfe hstory forms wthn the speces,.e., sea-run form and fluval form (Kato 1991). n the northern part of ther dstrbuton, most populatons conssted of sea-run fsh and some fluval male (mature male parr). n populatons around the southern lmt of ther dstrbuton, all males and females have a fluval lfe cycle. Moreover, throughout ther dstrbuton, lake-run form has occurred n lakes constructed artfcally by dams or by ntroducton to natural lakes whch masu salmon dd not orgnally nhabt (Osana 1962, Honda et al. 1980, Yamamoto et al. 2000). Many researchers have reported on the lfe-hstory of the sea-run form (e.g., Kubo 1980, Mayama 1992, Kso 1995) and fluval form (e.g., Kmura 1989, Kso 1995). n lacustrne populatons, there are some reports on the food habts (Osana 1962, Honda et al. 1980) and sze and age at maturty (Honda et al. 1983, Yamamoto et al. 2000). However, lttle s known about lfe-hstory trats and the lfe cycle of lacustrne populatons, except that Yamamoto et al. (2000) reported on the male lfe cycle n Toya Lake, northern Japan. We descrbed here several lfe-hstory trats of masu salmon n Shumarna Lake, northern Hokkado, Japan, and estmated ther lfe cycle. Study area and Methods Shumarna Lake, 23.7km 2 surface area and 31m maxmum depth, s located n northern Hokkado (Fg. 1) and was artfcally constructed n 1943 by dammng the upper reach of the Uryu Rver (shkar Rver-System) for a hydroelectrc power. Masu salmon land-locked by the dam orgnate from the Uryu Rver fsh (Osana 1962). n addton to masu salmon, Japanese smelt Hypomesus npponenss (ntroduced), Japanese huchen Hucho perr, whtespotted charr Salvelnus leucomaens, Japanese dace Trbolodon hakonenss, carp Cyprnus carpo (ntroduced), and crucan carp Carassus aura thus (ntroduced) nhabt n Shumarna Lake (Osana 1962, Tamate unpubl. data). From 1996 to 1999, samplng were performed n two nlet streams (Bfukakoshzawa Creek and Akash Creek) by electrofshng, cast net and anglng. Smolts were captured from md-may to early-july. Mature parr (wth typcal parr marks) and lake-run adults (wthout clear parr marks) were collected from late-july to md-september. All fsh measured were raw. Fork length and body weght of each fsh were measured, and ther sex and degree of rpeness were examned by drect observaton of the gonads. Scales were used to determne age and spawnng marks noted (Kso 1995). Data n each (Receved; Mar. 14,2000: Accepted; June 16, 2000) * Correspondng author: tamate@exfor.agr.hokudalac.jp

3 40 Tamate, T. and Maekawa, K. Eurasan J. For. Res. 1 (2000) E! 1 45 N N E! Creek Hokkado s. Q lkm + N Fg. L Map of the Shumarna Lake system. year were pooled because of small number of ndvduals collected. We also analyzed parr captured n the lake by nets used to collect Japanese smelts by a fsherman. Results and Dscusson Of smolts collected (N = 59), 84.7% were 1+ and 15.3 % were 2+. Most of smolts conssted of females: 78.0% of 1 +smolts (39 50) and 88.9% of 2+ smolts (8 9) were females. The 1 +smolts tended to be smaller n body sze than 2+smolts (Fg. 2A. mean fork length n 1 +smolts = 126.1mm±9.4 S.D., N = 50; 2+smolts 138.6± 10.9, N = 9; Mann-Whtney U-test, U = 78.0, P <0.002). Age composton, sex rato and sze of smolts n Shumarna masu salmon appear to be smlar that of sea-run populatons n Japan (see Kato 1991). All of 78 mature parr examned were male. Of these male parr, 36 (46.2%) and 41 (52.6%) were 0+ and 1 +, respectvely. Only one ndvdual was 2+ (2.2%). Sze of parr ncreased wth age at maturty (Fg. 2B. O+parr = 108.4± 10.6, N = 36; 1+parr = 153.0±17.5; N = 41; 2+parr = 243.0, N = 1). Some of 1 + and 2+ parr had a spawnng mark n the prevous year n ther scales (no. of ndvduals havng spawnng mark n 1+ parr = 5, n 2+parr =1): thus, some mature parr wll survve after the frst breedng and mature agan n the next autumn. Of the 51 lake-run adults collected, 2+ females and 2+males were 30 (58.8%) and 15 (29.4%), respectvely. The 3+ females and 1+ males were few (3+females 7.8%, 1+ males 3.9%). Thrty four (66.7%) of lake-run adults were females. Excludng the occurrence of 1 + lake-run males, age composton and sex rato of lake-run adults do not appear to dffer n comparson wth that of sea-run populatons n Japan (see Kato 1991). Lake-run females tended to be larger than lake-run males (Fg. 2C. 2+females = 347.2±27.8, N = 30; 3+females = 353.8±11.1, N = 4; 1+males = 197.5±10.6, N = 2; 2+males = 290.3±40.7, N = 15; females vs. males, Mann-Whtney U-test, U = 58.5, P < 0.001). Accordng to Kato (1991), the mean fork length of sea-run adults ranged from 375mm (males, Tokoro Rver, Japan) to 660mm (males, Samarga Rver, Russa), usually more than 450mm. Thus, the body sze of mgratory adults n Shumarna Lake was extremely small, compared wth that of sea-run populatons. Ths appears to be due to low food abundance (due to low producton of Japanese smelts) and relatvely low water temperature for longer perods (due to freezng over durng the wnter) n Shumarna Lake (see Tamate and Maekawa 2000). No lake-run adults had spawnng marks of the prevous year n ther scales; all lake-run adults de after breedng.

4 Masu salmon n shumarna Lake 41 Thrty four parr were captured n the lake from late-may to late-october, and conssted of O+parr, 1 + mmature parr and 1 + potental mature parr whch were judged to mature durng the year of capture (range of fork length n O+parr = mm, N =13; 1 + mmature parr = mm, N = 17; 1 + potental mature parr = mm, N = 4). Most of 0+ parr conssted of females (rato of females n 0+ parr = 84.6%), but such a trend was not recognzed n the 1 + mmature parr (52.9%). Some of these fsh may became smolts n the next year. The 1 + potental mature parr were males, and may mgrate up to nlet streams before spawnng season, socalled "puerle" (Yamamoto et al. 2000). n Toya lake, whch s located n southwestern Hokkado, Japan, "puerle" usually occur (Yamamoto et al. 2000). However, n Shumarna Lake, few puerle males appear to occur because they have rarely been caught n the lake. The lfe cycle of lake-run masu salmon s smlar to that of the sea-run populatons, whch nclude both the semelparous mgratory females and males and the teroparous stream-resdent males. However, two partcular lfe cycles probably occur n Shumarna masu salmon. n anadromous masu salmon, the parr undergo smoltfcaton n the sprng and mgrate to the sea after the juvenle parr lve for one or two years n rvers. They return to ther natal streams after 1 yr of marne lfe (e.g., Kubo 1980, Kato 1991, Mayama 1992, Kso 1995). n Shumarna Lake, a few juvenle parr mgrate to the lake. Therefore, some fsh wll smoltfy n the lake durng the next sprng and spend about two years n the lake (thus, two years of lacustrne lfe). Another unque lfe cycle s that Jack, whch s a precocous lake-run male and do not wnter n the lake after smoltfcaton, occur n Shumarna Lake system. There are no reports of maturng anadromous masu salmon whch dd not wnter n the sea (Kato 1991), except that Tsger et al. (1994) reported on the occurrence of Jack n South Prmor'e, Russa. These lfe cycles may be pecular to lacustrne populatons. Acknowledgements We are grateful to the members of the Fsherman's Socety at Lake Shumarna, especally K. Uto and N. Nakano, for ther assstance. We could not have accomplshed ths study wthout the assstance of the staff of the Uryu Expermental Forest and many graduate and undergraduate students at Hokkado Unversty. Ths research was supportted by a grantn-ad from the Mnstry of Educaton, Scence, Sports and Culture (No ) and the Mnsry of Agrculture, Forestry and Fshery. C) +o A) = 59 o l+faaale 2+faaale.1Gle [] 2Ge Fork length (om) l+11ale Fg. 2. Fork length dstrbuton of A) smolts, B) mature male parr, and C) lake-run adults caught n Bfukakoshzawa Creek (smolts caught ll Akash Creek. also) from 1996 to References Honda, N., Suzuk, A., Amta, K., Kataoka, T. and Emura, K. (1980) Studes on the reproducton of landlocked masu salmon, Oncorhynchus masou (Brevoot), n Okutadam reservor.. Vertcal dstrbuton and feedng habts of fsh (land-locked masu salmon, etc.). Rep. Ngata Pref. nland Water Fsh. Exp. Stn., 8: (n Japanese wth Englsh summary). Honda, N., Kataoka, T., Hoshno, M. and Sek, Y. (1983) Studes on the reproducton of landlocked masu salmon, Oncorhynchus masou (Brevoot), n Okutadam reservor. V. Studes on the growth and age of maturty of the land-locked masu salmon n Okutadam reservor. Rep. Ngata Pref. nland Water Fsh. Exp. Stn.,10: (n Japanese wth Englsh summary). Kato, F. (1991) Lfe hstores of masu salmon and am ago salmon (Oncorhynchus masou and Oncorhynchus rhodurus). n "Pacfc Salmon Lfe Hstores" (ed. by C. Groot and L. Margols), UBC press, pp , Vancouver. Kmura, S. (1989) The Yamame, land-locked masu

5 42 Tamate, T. and Maekawa, K. Eurasan J. For. Res. 1 (2000) salmon of Kyushu sland Japan. Physol. Ecol. Japan., Spec. 1: Kso, K. (1995) The lfe hstory of masu salmon Oncorhynchus masou orgnated from rvers of the pacfc coast of Northern Honshu, Japan. BUll. Natl. Res. nst. Fsh. Sc., 7: (n Japanese wth Englsh summary). Kubo, T. (1980) Studes on the lfe hstory of masu salmon (Oncorhynchus masou) n Hokkado. Sc. Rep. Hokkado Salmon Hatchery, 34: 1-95 (n Japanese wth Englsh summary). Mayama, H. (1992) Studes on the freshwater lfe and propagaton technology of masu salmon Oncorhynchus masou (Brevoot). Sc. Rep. Hokkado Salmon Hatchery, 46: (n Japanese wth Englsh summary). Osana, M. (1962) Ecologcal studes on the landlocked masu salmon, Oncorhynchus masou (Brevoot). 1. Ecologcal successon of the lmonologcal condtons and feedng habt of the lake-locked form at Uryu reservor. Sc. Rep. Hokkado Fsh Hatchery, 17: (n Japanese). Tamate, T. and Maekawa, K. (2000) nterpopulaton varaton n reproductve trats of female masu salmon, Oncorhynchus masou. Okos, 90: Tsger, V. V., Skrn, V.., Krupyanko, N.., Kashkn, K. A. and Semenchenko, A. Yu. (1994) Lfe hstores forms of male masu salmon (Oncorhynchus masou) n South Prmor'e, Russa. Can. J. Fsh. Aquat. Sc., 51: Yamamoto, T., Edo, K. and Ueda, H. (2000) Lacustrne forms of mature male masu salmon Oncorhynchus J1la.SJ.2U Brevoot, n Lake Toya, Hokkado, Japan. chthyologcal Research (n press).