Supplementary material

Appendix A. Population biomass of the age 0+ vendace and age 0+–2+ whitefish in autumn in 1979–2018 in Lake Pyhäjärvi. Vendace data from Sarvala and Helminen (2021). The period of vendace overfishing indicated with a horizontal blue bar. The horizontal red bar shows the average whitefish biomass during that period.

Appendix B. Biomass ratio between zooplankton and planktivorous fish (food availability index, FAI), and the density of whitefish larvae in 1987–2019 in Pyhäjärvi. Broken and dotted curves represent smoothing by 4^th order polynomial.

Appendix C. Annual catches of signal crayfish from Pyhäjärvi in 2000–2022 (Source: Säkylän Pyhäjärven hoitoyhdistys).

Appendix D. Population biomass in autumn of (A) whitefish, (B) vendace, (C) perch, (D) roach, (E) smelt and (F) ruffe in Pyhäjärvi in 1988-2018. Trend lines and 95% confidence limits are shown for significant regressions of biomass vs time (NS = not significant).

Appendix E. Average June–September temperature (A), total phosphorus (B) and chlorophyll a (C) at 0–2 m depth in 1982–2020 in Pyhäjärvi. Broken lines show the trendlines.

Appendix F. Whitefish larval density with bootstrapped 95% confidence intervals plotted against the hatching year. Also shown are the expected values predicted from population fecundity (PF) of the previous autumn alone or in combination with the signal crayfish egg predation during spawning time and winter (PF & Scf).

Appendix G. Proportions of various food items in the diet of age 1+ (A) and age 0+(B) whitefish in 1989 in Pyhäjärvi.

Appendix H. Development of the annual ratio between catch and population biomass of whitefish in Pyhäjärvi in 1988-2018. In the 1990s, the ratios were very high, declining clearly with increasing scatter towards the end of the time series. Although the catch/biomass ratios in the early part of this time series were unrealistically high, they suggest that the high fishing pressure on whitefish has relaxed during the latest years.

© J. Sarvala et al., published by EDP Sciences, 2024