Painting a fuller picture of human marine exploitation
To better gauge the health of a marine ecosystem, scientists need to be able to measure how things have changed. Are there fewer fish, or fewer fish species than before? Has the size – and thus the age at which fish are being caught – decreased? “The difficulty here is that scientific observations often only go back a few decades,” explains SeaChanges project coordinator David Orton from the University of York in the United Kingdom. “This brings into play the shifting baselines concept. If you are trying to assess if a particular ecosystem is depleted, you might go back to scientific data from 20 years ago. But if you were to ask somebody from then to assess the situation, they would be comparing the situation to a baseline further back, and so on.”
Case studies on human marine activities
The SeaChanges project came about out of a realisation that longer-term trajectories could better capture how centuries of marine exploitation have impacted fish stocks. To do this, 15 case studies were undertaken by PhD students, with the support of the Marie Skłodowska-Curie Actions programme. These case studies all took long-term perspectives on human marine activities, with timescales ranging from decades to millennia.
Long-term perspectives on ecosystems
One case study for example looked at North Sea cod fishing. Industrialised fishing began in the late 19th century with steam-powered trawlers, which massively increased the amounts of fish that could be extracted. Through the study of mitochondrial DNA, the study was able to show that while overall populations of cod might have been suppressed since industrialisation, there has not been a great loss of genetically different subgroups – potentially good news for restoration efforts. Another case study looked at dolphin populations around the Iberian Peninsula. Through an examination of historical documentation – for example about organised culls – the researcher was able to gain a clearer picture of the amount of dolphin biomass taken out of the ecosystem as a result of persecution. “Another project focused on grouper populations and fish sizes in the eastern Mediterranean since the Bronze Age, in part through the application of collagen fingerprinting techniques,” says Orton. “Other studies looked at population dynamics of Baltic herring since the Viking Age, as well as the changing length of Atlantic bluefin tuna.”
Broader narrative of human activities
Together, these separate case studies have built up a broader narrative of human marine exploitation. “I think that shifting the mindset of the general public has as much relevance as it does for policymakers and practitioners,” adds Orton. “We’ve drawn attention to the fact that, while there has been long-term exploitation of the seas, for many species in many waters, there has also been a clear step change in terms of fishing intensity.” The project has also helped to shine a light on the economic history of Europe. Marine resources have been fundamental to European development, and SeaChanges helped to demonstrate this. One study for example showed that flatfish were harvested from marine waters far earlier than previously thought. Moving forward, Orton would like to see more dialogue fostered between different academic disciplines and fisheries managers. “Archaeologists don’t always understand what the fisheries sector needs, while fisheries scientists and marine biologists often don’t understand the challenges faced by archaeologists,” he says. “By training people up to understand both sides, I hope that we’ll be in a better position in the future to tackle all these issues.”
Keywords
SeaChanges, marine, archaeological, fisheries, ecosystem, DNA, dolphin, cod
