However, the rapid development in aquaculture fish production has not been matched by new methods that accurately can trace the food chain supply in aquaculture production.With stable isotope fingerprinting, an international team lead by researchers from Kiel University and the Kiel Cluster of Excellence "The Future Ocean" has developed a new method for identifying the protein sources of salmon with high accuracy.In this way, conclusions can be drawn about the origin and nutrition of individual fish.The results of the study were recently published in the international journal Food Chemistry.New isotopic analyses of bones, soils and plant remains from Rapa Nui, Chile (Easter Island) provide evidence contrary to the widely-held belief that the ancient civilization recklessly destroyed its environment.It had been proposed that vast forests of giant palm trees were cut down by the people of Rapa Nui leaving them among other things without canoes.In recent years, commercial compound diets in aquaculture have gone from a single source of protein, fishmeal, and a single source of lipid, fish oil, to more than several dozen ingredients such as soy, insects, macroalgae, mussels and yeast.
To reduce costs and impact on wild fish stocks, carnivorous fish are increasingly fed plant-based diets in aquaculture.Professor Popp said: "Human and animal bone retain isotopic ratios that reflect a consumer's diet in life."By studying these isotope ratios, particularly in individual amino acids, we estimated the relative proportions of different food sources in each individual’s diet." Christian-Albrechts from the University of Kiel Thomas Larsen, added: "We used three independent lines of isotopic evidence to determine what the ancient Rapa Nui people ate.These had been carefully constructed and deliberately managed, and our study showed that the islanders may have added fertilisers." The research team analysed archaeological material dating from 1400AD to the historic period from the Kon Tiki Museum in Oslo, Norway.These included some material from excavations lead by the famous Norwegian explorer and anthropologist Thor Heyerdahl in the 1950s and 1980s.Contrary to notions of 'ecocide', the new results suggest that the ancient population adapted to the harsh environmental conditions by managing their gardens and manipulating soils for better crops. This means that they exhibited astute environmental awareness and stewardship to overcome nutrient poor soils. Catrine Jarman concluded: "This research highlights the unique and varied environmental adaptations that Pacific Islanders have shown through time. "Polynesians developed sustainable economies in ways that we are now better understanding through interdisciplinary research. The ecocide hypothesis, though controversial, is commonly used as the archetypal parable of the dangers of environmental destruction. In addition to offering specialized courses, the ITCE funded Catrine Jarman's Research-in-Residence at the University of Hawai‘i allowing her to gain access to new ideas, skills and data through collaborative work with Popp, an ITCE course faculty member.Understanding how past populations managed their limited resources for subsistence purposes is crucial to this debate, but empirical evidence of their diets is sparse. Funding was also obtained through a research grant to Jarman from the Kon-Tiki Museum.