This study verifies the food assimilation of a carnivorous teleost in different timescales (weeks vs months) and evaluates how it uses the food sources. The target species is the adult ribbonfish, Trichiurus lepturus, a voracious teleost caught in commercial fisheries off south-east Brazil (21°S–22°S). The isotope models indicated Chirocentrodon bleekerianus as the main food in the ribbonfish diet in the last weeks (liver: 38.5%; 95% credible intervals: 3.4–73.9%) and last months (muscle: 36.2%; 95% credible intervals: 3.4–68.7%). The contribution of other food sources ranges from 10–16% (liver) and from 10–20% (muscle). Food assimilation remains similar at different timescales. The isotope models suggested a strong and long-lasting association of the adult females of ribbonfish with coastal waters along the study area.

The shallow sandy marine subtidal ecosystem off Mar del Plata, Argentina, is the scene of multiple fisheries activities, in particular the prawn–shrimp Artemesia longinaris and Pleoticus muelleri grounds. We examined the δ13C vs δ15N isotope signatures of 22 species commonly found in the area in order to understand how this ecosystem supports the fishery, with special emphasis on imposex-affected gastropod populations. Our results indicate that the main food source for Olivancillaria urceus and Buccinanops monilifer were bivalves and crustaceans. Buccinanops duartei and Olivancillaria carcellesi feed on bivalves and also on macroalgae. These findings indicate, for the first time, a slight selectivity of some of the gastropods studied for local drifted algal sources and how gastropods may scavenge available food from by-catch returned to the sea. The fishes Urophysis brasiliensis and Callorhynchus callorhynchus appeared to be the top predators of this area with B. duartei and O. carcellesi constituting important components of their diet.

Viking Haithabu and its successor, the medieval town of Schleswig, were important international trade centres. Human skeletal finds spanning a period of approximately 400 years represent the bodily relics of the former inhabitants, who witnessed the rise and fall of these trade centres. Analysis of δ13C and δ15N from bone collagen was performed to reconstruct and detect changes in dietary preferences over time. A comparison with the respective isotopic data obtained from a large archaeofaunal sample resulted in a classic ‘mixing muddle’ that could only be deciphered using isotope mass balance mixing models applied on an individual basis. It was found that the overall subsistence economy shifted over time from a focus on fishing to one based predominantly on farming. The move to utilizing a new main source of protein did not impair overall protein supply. In addition, changing living conditions experienced by the inhabitants of Schleswig may have led to a change in infant nursing strategy.