Possible impacts of environmental change on pelagic fish recruitment: modelling anchovy transport by advective processes in the southern Benguela

Climate change may influence pelagic fish by altering advective processes or by changing where fish choose to spawn. Using a simulation model, the effects of altered advection and spatial distribution of spawning by anchovy on recruitment off South Africa were explored. Cape anchovy Engraulis capensis spawn on the region of the Agulhas Bank, south of South Africa. Currents transport eggs and larvae to nursery areas. Transport of eggs and larvae was modelled using a flow field based on averaged Acoustic Doppler Current Profile data, Feasible Scenarious of altered advection were modelled. For modelling purposes, the ocean surrounding South Africa was divided into blocks with dimensions of a quarter‐degree latitude by a quarter‐degree longitude. Acoustically measured distributions of spawner biomass for the years 1986–92 were used to calculate egg production per block. In the model, batches were released from each of these blocks each day of the spawning season. The modelling study indicates that passive transport of young anchovy may account for a substantial proportion of year‐class variability. Model results show that distribution of spawners influences the distribution of young of the year, as well as the number and the location of advective losses across offshore boundaries.