Scenario simulations (2016–2098)

During the scenario simulations, we varied the same forcing variables (Table 1, Fig. S2) used to force the model in the historical period. Table 2 details the seal abundance, F_cod and environmental scenarios used in the future projections (2016–2098). In the seal0 and seal1 scenarios, we used seals as ‘forcing’, i.e. set their biomasses to certain values a priori, excluding bottom-up effects affecting their biomass. In seal50, we forced the seal biomass to grow exponentially, following the current growth trend, until a maximum seal population size of 50 times the initial biomass from 1974, which is past the number of seals that there were in the Baltic Sea in the beginning of the twentieth century [nearly 100 000 individuals (Harding and Härkönen 1999)]. This is followed by a stabilization of seal biomass around 2 040 of 0.07 t km⁻² or 140 000 individuals (Fig. S3). The Multi-sim functionality of Ecosim was used to simulate the dynamics of the groups from 2016 to 2098 for each of the future scenarios. Linear models were fitted to the log-transformed model outputs for the period 2016–2098 to investigate how the environmental, F_cod and seal abundance scenarios affect the mean annual biomass, catches, seal consumption and fish predation mortality by seals of adult cod, herring and sprat in each scenario combination (Fig. S4). No carrying capacity limits were set for any of the functional groups.