Figure 4
Hysteresis and stable states in Western Baltic cod. (a) Effect of scaled exploitation pressure, i.e. fishing mortality (F) relative to recruitment (R, i.e. year-class strength at age 1), and sea surface temperature (SST) on spawning stock biomass (SSB; points scaled to predictions from stochastic cusp modelling); grey shaded polygon indicates the cusp area where bistability of the system exists. (b) Time-series on observed (grey dashed line) and predicted SSB (points and black solid line) from stochastic cusp modelling; horizontal coloured bars indicate SSB regimes (see Fig. 1). In (a) and (b) red points indicate the system to be in the bistable cusp area (see polygon in a) and black points indicate a stable system, outside the cusp area.
