Clues from the past to guide the future
Eric is casting back in time to understand how processes throughout history have shaped shark ecology today. Based in Monterey Bay, where declines in the 21 different local shark species have been attributed to overfishing and environmental change, he is using archaeological sites to understand thousands of years of shark history. Using ancient DNA to confirm species identification for shark remains, and combining this with cutting-edge biogeochemistry, Eric aims to look at how overfishing and habitat change have impacted shark behaviour over a much greater timescale than ever before. His hope is that his results will add nuance to how shark conservation is approached.
Eric Guiry
I grew up in the Great Lakes region of Canada and spent my childhood exploring the Lake Ontario watershed. On visits with family in the USA I would catch fish along Florida beaches. During this time I had the privilege of observing a wide range of marine and freshwater life: reptiles, amphibians, crustaceans and fish. These experiences came to underpin my lifelong interest in understanding how human and animal communities interact. Throughout my graduate studies – including two BScs, an MA, and a PhD focusing on natural science and archaeology – I had further opportunities to live near and study...
Towards an archaeology of sharks: building millennial-scale records of shark ecology in Monterey Bay
To demonstrate the immense potential of archaeological shark remains as bio-molecular archives for exploring long-term trends in shark ecology.
Humans have been exploiting sharks for millennia. However, because scientific monitoring has developed only recently, conservation decisions about how to protect sharks are often made with limited knowledge of how populations have responded to past and ongoing human impacts, like overfishing and habitat destruction. To better contextualise key conservation challenges, such as knowing which human impacts are most harmful to shark populations, this project taps into the potential of archaeological assemblages for generating long-term baseline perspectives.
Monterey Bay, on California’s Central Coast, supports more than 500 fish species, including 21 shark taxa. Although many of the bay’s sharks were once abundant, a growing number of species have seen reductions in their populations as a result of overfishing and the deterioration of their environment. Several research programmes are exploring contemporary shark ecology in the area, but they lack the time depth necessary to understand the long-term impacts of the historical processes that have shaped (and continue to shape) modern shark ecology in the region.
Shark remains recovered from archaeological sites around Monterey Bay provide unprecedented opportunities to explore the relationships between sharks, humans and the environment over hundreds or even thousands years. This promising avenue of research is almost entirely unexplored, however, due to difficulties in assigning species identifications to archaeological shark remains, which prevents more detailed analyses. Our project will overcome this challenge by using analyses of ancient DNA to confirm species identification for the shark remains. Combining species identifications with cutting-edge biogeochemical techniques will enable us to investigate long-term patterns in shark behaviour and explore the effects of long-term processes (like overfishing and habitat change) on Monterey Bay’s shark ecology for the first time. Insights from this work will provide key contextual information for developing more nuanced shark conservation approaches.
- To use archaeological science techniques to reconstruct how fisheries have impacted shark populations over millennia. This information can be critical for improving how we approach shark conservation challenges.
RESULTS:
Our finding provides the first glimpse of the potential for combined biomolecular approaches to shed light on the past ecology of sharks and the evolution of human-shark relationships. While this has, overall, been a small pilot project, results already hint at possible continuity in population dynamics among Tope Sharks (aDNA) and habitat preferences for Leopard Sharks in the Monterey Bay area. This project has also helped us to understand some of the challenges that will be inherent in retrospectively oriented conservation research that seems to generate long-term behavioral baselines using archaeological materials. In particular, future work would benefit from larger sample sizes as well as taking an iterative approach in which aDNA is performed on a much large suite of samples in order to allow selection of statistically meaningful sample sizes from target taxa with ecologies that are better suited to exploration through isotopic analyses.
Nonetheless, it should be noted that our historical dataset is not directly comparable with the modern dataset, limiting the strength of our conclusions. The modern sample includes individuals from multiple areas of Southern California while our archaeological samples represent individuals from a single region in Central California. While North American Tope Sharks are considered a single population, if a subpopulation existed in the past genetic differences between modern and historical samples might reflect geographical rather than temporal differences. This, in turn, could explain why some haplotypes present in the modern sample are absent from the ancient population. As such it is, while we believe these findings could represent an exciting discovery, we are planning to further analyses from sites across a wider geographical area to confirm interpretations.