Gadiform species display dietary shifts in the Celtic Sea

Global changes, through their impacts on ecosystem trophic structures, are behind regime shifts and cascading effects, and could result in the reorganization of whole ecosystems. The Celtic Sea is a temperate sea at risk of the above because of the interplay between climate change and fisheries. This sea has only displayed slight changes in species diversity between the late 20th century and the present day. However, this apparent stability in species diversity could be hiding structural transformations, including the rearrangement of trophic relationships. Historical stomach content database offers the opportunity to investigate changes in ecosystem trophic structure. Based on such database, this study explored shifts in the feeding habits of gadiform species in the Celtic Sea in the 1980s, 1990s, and 2010s. To this end, it examined dietary generalism and composition for four top predator fish species. During the target period, generalists maintained their diets, while specialists adopted more generalist diets. There were also decreases in frequencies of occurrence of certain fishes within the diets of gadiform species. These recent changes in trophic structure organization have likely been caused by the influence of global changes on both top-down and bottom-up processes that occurred in the Celtic Sea.