A decline in the energy content of forage fish in the Bay of Biscay

Planktonic production fuels the base of marine food webs and can mediate energy accumulation in consumers but is affected by several anthropogenic pressures. Our understanding of how shifts in prey quality at various trophic level shape marine food webs remains poor. This study explores variation in the nutritional quality of prey of hake Merluccius merluccius and whiting Merlangius merlangus between the 2000s and 2020s. An overall decrease in prey quality was observed between these periods. Prey species previously considered high quality no longer differed in nutritional composition from intermediate-quality prey species. These results suggest that a profound trophic reorganization is currently taking place in the Bay of Biscay, probably mediated through bottom-up processes.