Synergistic effects of fishing-induced demographic changes and climate variation on fish population dynamics

The synergistic effects of fishing, climate internal dynamics on population fluctuations are understood due to the complexity of these interactions. this paper, we combine time series analysis and to investigate the long-term dynamics of overexploited population in the Mediterranean Sea, its link with both fishing-induced demographic and hydroclimatic variability. We show that the of the catch per unit of effort (CPUE) of European Merluccius merluccius (EH) vanished in the1980s, while the correlation between the CPUE and a environmental index increased. Using simulations, then show that the cyclicity observed in the EH biomass the 1980s can have an internal origin, while its disappearance could be due to the fishinginduced of the age structure. Our results suggest fishing can trigger a switch from internally generated externally forced population fluctuations, the being characterised by an increasing dependency the population on recruitment and ultimately on environmental. Hydroclimatic modifications occurring the Mediterranean in the early 1980s could enhanced these changes by leading to a mismatch early life stages of EH and favorable environmental. Our conclusions underline the key of the interaction between exploitation and climate the dynamics of EH and its important consequences management and conservation.