Anchovy biomass is linked to annual potential new production in the southern Benguela: Support for the 'optimal environmental window' hypothesis

Abstract

The hypothesis that physical forcing is related to tertiary production was tested by relating regional estimates of annual potential new production to certain pelagic fishery variables. The results show strong evidence of a dome-shaped relationship between annual potential new production (x-axis) and anchovy spawner biomass (y-axis), providing further confirmation that both a paucity and surfeit of upwelling is detrimental to the fishery. Fish biomass was maximized by a median range of upwelling, which formed an 'Optimal Environmental Window' either side of the dome apex. The relationship was described by a Gaussian Area curve: y = 1.90 e([0.5(x-5.72)/0.43)2]·) (r2 = 0.90) A similar, but less marked, dome-shaped relationship was found with respect to anchovy recruitment biomass. It is shown that the period of physical forcing most likely to impact on anchovy recruitment on the west coast of South Africa is negatively correlated with recruitment biomass.