Sea of Japan Hokkaido Okhotsk Sea Study area Number of fish released (thousand) 120,000 100,000 80,000 60,000 40,000 20,000 0 1991 1993 1995 1997 1999 2001 Year Fish released in rivers Fish released from net-pens

Number of fish released (thousand) 12,000 10,000 8,000 6,000 4,000 2,000 0 1 10 20 30 10 20 May June Date Return rate (%) 20 18 16 14 12 10 8 6 4 2 0 1991 1992 1993 1994 1995 1996 1997 Year 1998 1999 2000 2001 Mean weight (g) Return rate (%) 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 Mean weight at release (g)

Return 8-days period (counted consecutively by defining 1-8 January as the first) Year of rate 17th 18th 19th 20th 21st 22nd 23rd 24th 25th release (%) 9-16 May 17-24 May 25 May-1 Jun 2-9 Jun 10-17 Jun 18-25 Jun 26 Jun-3 Jul 4-11 Jul 12-19 Jul 1991 10.7 1992 6.9 No Data No Data 1993 8.6 1994 13.4 No Data 1995 9.4 1996 5.3 1997 5.6 1998 10.5 1999 9.6 No Data No Data No Data No Data No Data No Data 2000 17.7 2001 11.5 Period of SST within 8-13 No Data

20 20 Return rate (%) 15 10 5 0 y = -3.15x + 73.63 R 2 = 0.60 P < 0.01 18 19 20 21 22 First period reaching 8 Return rate (%) 15 10 5 0 y = -2.08x + 59.79 R 2 = 0.41 P < 0.05 21 22 23 24 25 26 27 First period exceeding 13

20 17th 8-days period (9-16 May) 20 18th 8-days period (17-24 May) 19th 8-days period (25 May-1 June) 20 Return rate (%) 15 10 5 0 y = -0.13 x + 10.04 R 2 = 0.004 P > 0.05 0 2 4 6 8 10 12 14 SST Return rate (%) 15 10 5 0 y = 0.49x + 7.28 R 2 = 0.023 P > 0.05 0 2 4 6 8 10 12 14 SST Return rate (%) 15 10 5 0 y = 3.10x - 12.29 R 2 = 0.58 P < 0.05 0 2 4 6 8 10 12 14 SST Return rate (%) 20 15 10 5 20th 8-days period (2-9 June) y = 0.11x + 9.13 R 2 = 0.002 P > 0.05 Return rate (%) 20 15 10 5 21st 8-days period (10-17 June) y = 0.31x + 6.99 R 2 = 0.020 P > 0.05 0 0 2 4 6 8 10 12 14 SST 0 0 2 4 6 8 10 12 14 SST

1991 1996 1997 2001

Upper marking reach Falls Sea of Japan Hokkaido Pacific Ocean Hidarimata River Lower marking reach Sea of Japan Atsuta River

1998 Number of fish 40 30 20 10 0 Late July Lower reach Male Female Upper reach Number of fish 40 30 20 10 0 Mid-August Male Female Lower reach Upper reach 1999 Number of fish 40 30 20 10 0 Late July Male Female Lower reach Upper reach Number of fish 40 30 20 10 0 Mid-August Male Female Lower reach Upper reach Number of fish 40 30 20 10 0 Late August Male Female Lower reach Upper reach

Number of fish 80 70 60 50 40 30 20 10 0 1998 Male Female 9/8-9 9/18 9/24 10/2 Number of fish 80 70 60 50 40 30 20 10 0 Male Female 1999 9/2 9/7 9/15 9/20-22 9/28-29 10/6

St.1 (6000m) Oyobe River 0 0.5 1.0 St.2 (4500m) St.3 (3000m) 44 N 42 N St.4 (1200m) St.5 (300m) 140 E Sea of Japan 145 E Sea of Okhotsk Hokkaido Pacific Ocean Tsugaru Strait

Frequency Frequency Frequency 100 80 60 40 20 0 100 80 60 40 20 0 100 80 60 40 20 0 0.3 1.2 3 4.5 6 0.3 1.2 3 4.5 6 0.3 1.2 3 4.5 6 Fork length ( cm ) Body weight ( g ) Condition factor 11.0 10.5 10.0 9.5 9.0 16.0 14.0 12.0 10.0 12.5 11.5 10.5 9.5 1-Oct 30-Nov 29-Jan 29-Mar Month Seasonal changes in the average fork le 1-Oct 30-Nov 29-Jan 29-Mar Month 1-Oct 30-Nov 29-Jan 29-Mar Month

Fork length ( cm ) Body weight ( g ) Condition factor 11.5 10.5 9.5 8.5 17.0 15.0 13.0 11.0 9.0 12.5 11.5 10.5 9.5 0 1 2 3 4 5 6 7 Distance of mouth ( km ) 0 1 2 3 4 5 6 7 Distance of mouth ( km ) 0 1 2 3 4 5 6 7 Distance of mouth ( km ) Stomach contents index 1.2 St.1St.5 1.0 0.8 0.6 0.4 0.2 0.0 A B,C B,D A,C,D D J F M Month 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 Water temperature ()

Stomach contents index 1.2 1.0 0.8 0.6 0.4 0.2 0.0 Dec.Mar. a,b St.1 St.2 St.3 St.4 St.5 a Sampling site b

Sea of Japan Date Fishing Port Kesen Dai-ichi Hatchery C.Chikyu Sea of Okhotsk Hokkaido Osaru R. Pacific Ocean Shiraoi Fishing Port 250Km Tomakomai Fishing Port

Mean body weight (g) 45 40 35 30 25 20 15 10 5-2001 2002 2004 11/1 11/21 12/11 12/31 1/20 2/9 3/1 3/21 4/10 4/30 5/20 2001 2002 2004 Number of individuals 35 30 25 20 15 10 5 0 50 40 30 20 10 0 24 May 22 Feb. 4 4 88 12 16 20 24 24 40 30 20 10 0 70 60 50 40 30 20 10 0 19 Feb. 4 4 88 12 16 20 24 21 May 40 30 20 10 0 50 40 30 20 10 0 1 March 4 4 8 8 12 16 20 24 21 May 10 10 30 30 50 50 70 70 90 90 110 130 130 10 10 30 30 50 50 70 70 90 90 110 130 10 10 30 30 50 50 70 70 90 90 110 110130 130 Body weight(g)

Number of fish 1 1050 50100 100 Sea of Okhotsk Number of fish 1 1050 50100 100 Sea of Okhotsk Sea of Japan Sea of Japan Pacific Ocean Pacific Ocean N=505 N=192

Number of fish 1 1050 50100 100 Sea of Okhotsk Number of fish 1 1050 50100 100 Sea of Okhotsk Sea of Japan Sea of Japan Pacific Ocean Pacific Ocean N=10 N=179 Number of fish 1 1050 50100 100 Sea of Japan Sea of Okhotsk Mean body weight(g) 3,000 2,500 2,000 1,500 1,000 500 - J J A S O N D J F M A M J Release year Next year Pacific Ocean N=62

Individual numbers m 2 Individual numbersm 2

1.0 1.0 0.8 R0 0.6 0.8 R0 0.6 0.4 0.4 0.2 Jul 2000 0.2 Oct 2000 1.0 1.0 0.8 R0 0.6 0.8 R0 0.6 0.4 0.4 0.2 Feb 2001 0.2 Apr 2001 1.0 1.0 0.8 R0 0.6 0.8 R0 0.6 0.4 0.2 Mar 2002 0.4 0.2 May 2002 1.0 1.0 0.8 R0 0.6 0.8 R0 0.6 0.4 0.4 0.2 Jul 2002 0.2 Oct 2002

e1 e2 e3 e4 0.01 0.20 0.23 0.59 Velocity at the Distance from Unfixed cobbles Water depth stream bed stream edge 0.12 0.45 0.48 0.00 0.77 e9 Physical environment e8 0.92 0.85 Total individual numbers 0.32 Benthic macroinvertebrates 0.88 0.77 Number of taxa 0.10 0.68 Total wet weight 0.46 e7 e6 e5