Long-term changes in productivity of conspicuous demersal species along the Peruvian and Chilean coasts using pre-image population analysis

Annual time series of biomass and/or abundance of Merluccius gayi peruanus (Peruvian hake), M. gayi gayi (Chilean hake), M. australis (Southern hake), Macrurorus magellanicus (Hoki) and Dosidicus gigas (Flying squid) were analyzed by pre-image population analysis (PPA). Through PPA, it was possible to estimate the equilibrium [x*] and intrinsic growth rate [r] values (this latter is used as proxy for productivity). The outcomes show that the Peruvian and Chilean demersal species exhibited a reduction (between  –17 and  – 97%) in both model parameters during the entire period of time analyzed. An exception was found for M. magellanicus (Hoki), which showed an opposite trend. Although practically all species exhibited an asymptotically fall in both model parameters, only the Peruvian hake seems to be in a better status. It is also highlighted that the Peruvian hake, Southern hake and the Flying squid showed chaotic dynamics with the highest equilibrium and growth rate (productivity) values. Consequently, it is suggested that changes of growth rate (productivity) values over time could be used as dynamic reference points for these demersal species. Finally, the PPA could be performed as a complementary analytic method, facilitating the monitoring of exploited or protected populations.