Synchronous multi-species alternations between the northern Humboldt and Kuroshio Current systems

Abstract Synchrony of species alternations in the northern Humboldt (NHCS) and Kuroshio (KCS) Current systems was examined by comparing time series data of landings and population statisticsof major small pelagic fish species along with climate indices from 1960 to 2015. Target species were anchovyEngraulis ringens , sardineSardinops sagax , jack mackerel Trachurus murphyiand chub mackerel Scomberjaponicus in the NHCS, and anchovyE. japonicus , sardineS. melanostictus , jack mackerelT. japonicus and chub mackerelin the KCS. The time series of total biomass and spawning stock biomass (SSB) of anchovyand sardinefor the NHCS and the KCS were well correlated, as were the landings data. Landings of small pelagic fish including jack mackereland chub mackerelindicated that multi-species alternations may also be synchronous at a community level between the two current systems. Peak landings of jack mackereland chub mackerelwere observed between peaks of anchovyand sardinein both current systems, although the relationships between jack mackereland chub mackereldiffered between the current systems. The species alternations between anchovyand sardineare most reasonably attributable to environmentally-induced changes in the biomass as a major mechanism, although the effect of fishing activity cannot be excluded. Future studies will be required to compare biological characteristics of multiple small pelagic fish species in the pelagic food chain in each current system.