Abstract
Understanding the extent and magnitude of change in marine food webs requires historical data that predates modern monitoring efforts. Such information can provide invaluable insights into the longer‐term impacts of altered trophic interactions, yet it is rarely incorporated into marine policy frameworks. Using multiple stomach records spanning over a century, we investigated long‐term changes in the diet composition of six demersal fish species in the western North Sea. Plaice, dab and haddock exhibited marked dietary shifts from larger, more sessile bivalves in the early 20th century to an increase in the prevalence of shorter‐lived, more opportunistic prey (polychaetes and echinoderms) in the latter part of the century. Cod, whiting, and grey gurnard exhibited variable diets, but some prey groups (amphipods and echinoderms) were consistently more important in particular decades. Compared to the 1900s, sandeels became an increasingly dominant dietary component for nearly all predators in later decades. These findings likely reflect ‘bottom‐up’ effects of altered benthic prey communities caused by the intensification of trawling, eutrophication and climatic changes, especially in the latter part of the 20th century. Our study highlights the value of using alternative historical data in detecting broad‐scale change over extended timescales, and provides additional evidence that can guide relevant policies aimed at restoring the functional integrity of marine food webs.