Data S1. Age distribution of whitefish catches from 1987 and 1990, estimation of a theoretical age distribution based on instantaneous mortality rate Z = 0,15, and estimation of relative year-class strength and mean values based on the two samples.

Year-class
Sampled 1987 / 1985 / 1984 / 1983 / 1982 / 1981 / 1980 / 1979 / 1978 / 1977 / 1976 / 1975 / Sum
Age / 2 / 3 / 4 / 5 / 6 / 7 / 8 / 9 / 10 / 11 / 12
Cn / 12 / 1 / 18 / 7 / 3 / 3 / 1 / 5 / 10 / 10 / 12 / 82
Cm / 14 / 12 / 11 / 9 / 8 / 7 / 6 / 5 / 4 / 4 / 3 / 82
YS / 84.5 / 8.2 / 171.1 / 77.3 / 38.5 / 44.7 / 17.3 / 100.6 / 233.8 / 271.6 / 378.7
Year-class
Sampled 1990 / 1988 / 1987 / 1986 / 1985 / 1984 / 1983 / 1982 / 1981 / 1980 / 1979 / 1978 / 1977 / 1976 / 1975
Age / 2 / 3 / 4 / 5 / 6 / 7 / 8 / 9 / 10 / 11 / 12 / 13 / 14 / 15
Cn / 28 / 9 / 3 / 8 / 0 / 2 / 4 / 3 / 4 / 3 / 6 / 8 / 10 / 4 / 92
Cm / 15 / 13 / 11 / 9 / 8 / 7 / 6 / 5 / 4 / 4 / 3 / 3 / 2 / 2 / 92
YS / 191.8 / 71.6 / 27.7 / 85.9 / 0.0 / 29.0 / 67.4 / 58.7 / 91.0 / 79.3 / 184.2 / 285.3 / 414.4 / 192.6
Mean YS / 191.8 / 71.6 / 27.7 / 85.2 / 4.1 / 100.1 / 72.3 / 48.6 / 67.8 / 48.3 / 142.4 / 259.6 / 343.0 / 285.7

Data S2. Data analysed by means of additive generalized modelling, YC = year, R = regulation regime (Old and New), mean air temperature in May to August (TM – A), water level mean one week after ice off (Watl), mean wind velocity four weeks after ice off (Winmean), time of ice over (Iceover), duration of ice cover (Icecover), time of ice off (Iceoff), time of water level minimum (Watmin) and estimated relative year-class strength of vendace (YV.0.15) and whitefish (YW.015) based on assumed instantaneous mortality Z = 0.15. Strong year-classes are bold faced.

YC / R / TM / TJn / TJl / TA / Watl / Winmean / Iceover / Icecover / Iceoff / Watmin / YSV / YSW
1969 / O / 8.5 / 15.8 / 16.9 / 17.5 / - / 1.1 / - / - / - / - / 607.7 / 68.8
1970 / O / 8.9 / 16.6 / 13.2 / 13.2 / - / 1.2 / - / - / - / - / 18.9 / 8.9
1971 / O / 8.1 / 11.6 / 14.0 / 12.2 / - / 1.1 / - / - / - / - / 5.4 / 32.5
1972 / O / 8.6 / 12.5 / 16.5 / 12.1 / - / 1.0 / - / - / - / - / 4.7 / 75.7
1973 / O / 8.1 / 14.0 / 15.6 / 11.6 / - / 1.1 / - / - / - / - / 18.9 / 198.0
1974 / O / 8.6 / 12.3 / 13.0 / 12.3 / - / 1.1 / - / - / - / - / 33.8 / 159.1
1975 / O / 8.8 / 12.0 / 16.1 / 15.2 / 436.36 / 1.3 / 1/1/ / 134 / 11/5/ / 21/4/ / 96.7 / 239.5
1976 / O / 9.4 / 13.0 / 15.6 / 13.5 / 437.57 / 1.2 / 2/1/ / 140 / 13/5/ / 16/4/ / 64.9 / 344.5
1977 / O / 7.6 / 12.4 / 13.7 / 12.3 / 437.12 / 1.4 / 29/12/ / 124 / 20/5/ / 23/4/ / 217.1 / 260.9
1978 / O / 8.4 / 13.7 / 13.4 / 11.9 / 435.62 / 1.1 / 9/12/ / 160 / 21/5/ / 30/4/ / 178.8 / 142.9
1979 / O / 6.7 / 14.1 / 12.8 / 11.2 / 435.16 / 1.2 / 12/12/ / 147 / 17/5/ / 21/4/ / 41.4 / 48.3
1980 / O / 8.7 / 14.2 / 14.9 / 12.7 / 434.42 / 1.4 / 12/12/ / 160 / 7/5/ / 18/4/ / 67.2 / 68.1
1981 / O / 9.7 / 11.1 / 14.1 / 11.9 / 436.24 / 1.3 / 12/12/ / 154 / 20/5/ / 12/4/ / 61.3 / 48.8
1982 / N / 7.7 / 11.6 / 16.1 / 13.8 / 435.84 / 2.5 / 31/12/ / 132 / 14/5/ / 19/3/ / 293.0 / 72.8
1983 / N / 9.0 / 12.7 / 15.8 / 13.5 / 437.30 / 1.5 / 6/1/ / 122 / 10/5/ / 8/4/ / 71.9 / 101.2
1984 / N / 9.9 / 12.6 / 14.1 / 13.3 / 434.67 / 1.6 / 5/1/ / 137 / 7/5/ / 12/4/ / 36.9 / 4.1
1985 / N / 8.3 / 12.8 / 14.1 / 12.5 / 435.94 / 1.8 / 9/12/ / 164 / 21/5/ / 19/4/ / 42.9 / 62.8
1986 / N / 9.0 / 15.2 / 14.9 / 10.6 / 437.59 / 1.8 / 30/12/ / 136 / 21/5/ / 24/4/ / 6.4 / 22.6
1987 / N / 6.9 / 10.9 / 14.6 / 10.7 / 435.83 / 1.4 / 19/12/ / 149 / 13/5/ / 24/4/ / 94.7 / 46.8
1988 / N / 9.0 / 16.1 / 14.9 / 12.7 / 434.91 / 1.3 / 16/12/ / 146 / 16/5/ / 22/4/ / 50.3 / 73.7
1989 / N / 8.4 / 13.6 / 15.2 / 12.0 / 437.09 / 1.7 / 28/12/ / 120 / 10/5/ / 6/4/ / 23.3 / 254.2
1990 / N / 9.7 / 13.5 / 14.0 / 13.4 / 436.40 / 1.8 / 12/1/ / 109 / 26/4/ / 15/3/ / 1.3 / 58.3
1991 / N / 7.9 / 10.0 / 16.2 / 13.9 / 434.24 / 2.8 / 10/1/ / 122 / 30/4/ / 2/4/ / 360.6 / 202.7
1992 / N / 11.2 / 15.1 / 14.1 / 11.6 / 435.71 / 1.3 / 21/12/ / 143 / 11/5/ / 4/4/ / 108.3 / 8.1
1993 / N / 9.9 / 10.8 / 13.5 / 10.8 / 437.15 / 1.7 / 14/12/ / 147 / 12/5/ / 7/4/ / 43.8 / 15.7
1994 / N / 7.7 / 11.5 / 18.9 / 13.3 / 434.98 / 1.5 / - / - / 9/5/ / 5/4/ / 76.7 / 8.5
1995 / N / 7.3 / 13.5 / 14.7 / 14.1 / 434.42 / 1.1 / - / - / 22/5/ / 10/4/ / 12.3 / 69.8
2001 / N / 8.6 / 15.9 / 15.8 / 13.1 / 435.16 / 1.5 / - / - / 11/5/ / 21/3/ / 11.9 / 27.8
2002 / N / 10.6 / 14.4 / 15.7 / 17.1 / 437.19 / 1.4 / - / - / 28/5/ / 27/3/ / 176.7 / 540.2
2003 / N / 8.2 / 13.9 / 17.1 / 13.8 / 435.03 / 1.3 / 30/12/ / 121 / 12/5/ / 14/4/ / 149.0 / 177.1
2004 / N / 10.0 / 12.7 / 14.1 / 15.0 / 435.03 / 1.8 / 16/2/ / 73 / 28/4/ / 11/4/ / 50.0 / 36.6
2005 / N / 7.2 / 12.3 / 16.7 / 13.3 / 433.58 / 1.6 / - / - / - / 5/4/ / 58.1 / 52.2
2006 / N / 8.4 / 14.7 / 17.7 / 15.5 / - / - / - / - / - / 12/4/ / 139.8 / 24.0
2007 / N / 9.1 / 15.1 / 14.6 / 14.0 / 434.65 / - / - / - / 28/4/ / 3/4/ / 25.6 / 6.6
2008 / N / 8.3 / 13.5 / 15.6 / 13.0 / 436.86 / 1.3 / 29/12/ / 124 / 10/5/ / 15/4/ / 44.2 / 137.3
2009 / N / 9.2 / 12.8 / 15.2 / 13.7 / 435.12 / 1.5 / 22/12/ / 139 / 1/5/ / 11/4/ / 75.4 / 137.9
2010 / N / 8.0 / 12.7 / 16.1 / 13.9 / 433.64 / 1.4 / 2/12/ / 144 / 9/5/ / 9/4/ / 216.5 / 67.8
2011 / N / 8.5 / 14.5 / 15.4 / 13.9 / 435.10 / 1.6 / 9/1/ / 110 / 24/4/ / 30/3/ / 134.0 / 87.6