March 2021
March 2021 - A look Into Historical Fisheries Through the Atlantic Cod- a Fish That Made History
Lourdes Martínez-García (ESR 1 - Oslo) and Rachel Blevis (ESR 2 - Cambridge)
There are many reasons to study the Atlantic cod.
For starters, it has a fascinating history and has been a key element in fisheries development since medieval times (1).
Secondly, though the Atlantic cod is not a particularly flashy fish, it is a keystone species in many marine environments (2).
It is also a successful predator, eating everything and anything in its path along the seabed, even plastic cups and other rubbish (3)!
Picture from ThisFish & Ecotrust Canada. Species, 2013.
http://thisfish.info/fishery/species/atlantic-cod/
Some Cod History
Before the 12th century, marine fishing and trade were popular activities for both coastal and inland communities in the North Atlantic Ocean. Atlantic cod is one example of a prominent marine trade-product since medieval times, thanks to air-drying and salting procedures which gave it an exceptionally long shelf life (4).
The archaeological remains of Atlantic cod and other fish species in the North Sea attest to an expansion of marine fishing activities and trade from Scandinavia to more southern waters in the 13th century (5). This expansion is also backed by written historical records and sagas. More distant trade began in the 15th-16th centuries with the discovery of Newfoundland and Labrador in the alleged “New World” (6). This discovery permanently changed the development of cod fisheries and turned them into globalized trade goods (7).
These extraordinary breakthroughs in marine enterprise are still worth researching, as many details of fishing expansion still elude us today. For instance, which other species were exploited and how intensively? Where exactly were these fish being exploited? What economic and ecological factors influenced these breakthroughs (e.g. increased urbanism, climate change, etc.)?
Atlantic cod has supported some of the most important fisheries of all time, which unfortunately led to population declines, unsustainable stock numbers and to categorization as vulnerable on the Red List of Threatened Species in 1994. Subsequently, strong conservation measures have been introduced to recover cod abundances and improve guidelines for more sustainable management (8).
So, what has intense commercial fishing done to this once abundant fish species?
The full extent of damage to contemporaneous fish stocks following historical fishing events remains unclear. Several new methods have been developed over the past 30 years to further explore the damage inflicted on Atlantic cod stocks. The recent improvements in ancient DNA analysis is one such method.
Why work with Ancient DNA Methods?
Lourdes Martínez-García (ESR 1 - Oslo)
Ancient DNA (aDNA) can provide impressive biological inferences, especially with time series analyses using a combination of historical and modern samples. The study of a wide-range of populations of Atlantic cod across different timelines is an excellent opportunity to understand the evolutionary potential of the species to overcome the current climate changes (9). With this in mind, a question arises:
Could early medieval fishing activities have influenced the decline of Atlantic cod more than we had originally thought?
The use of aDNA allows us to improve the accuracy of estimating changes in species distribution and population sizes both from recent centuries and from thousands of years ago (10). Reconstructing the history of fish trade between growing urban centers can also provide important insights on the role of such activities in the decline of Atlantic cod. Thus, understanding the historical events that species have experienced is vital for optimal conservation measures. Studying the aDNA of Atlantic cod will therefore offer vital information for future sustainable fisheries.
But wait! An interdisciplinary collaboration can add even more to the story of the Atlantic cod.
LabVideo No SoundmovPhoto and Video by Lourdes Martínez-García
Why work with Ichthyoarchaeological Methods?
Rachel Blevis (ESR 2 - Cambridge)
Zooarchaeological methods (e.g. morphometrics, skeletal-element representation analysis and species representation) can also help us understand our historical relationship with past cod populations. These methods have helped researchers reconstruct animal diets, trade networks, and vocations of past human populations from different social backgrounds and how they were interacting with their aquatic environments (11).
But how do we identify archaeological Atlantic cod-family bones to species? Can we also estimate how large they were in the past?
The unique morphological characteristics of Atlantic cod bones can help us identify their presence in the archaeological record, and the subsequent use of regression models and geometric morphometrics on cod vertebrae can help us reconstruct their past sizes.
The application of these methods to less-researched archaeological vertebrae can enhance our knowledge of past cod populations, especially during the early medieval shift to intensified marine fishing. It can also facilitate comparisons of estimated cod sizes from vertebrae elements in this study and cranial elements from past studies (12, 13).
Together, these methods constitute a comprehensive procedure for the identification and size reconstruction of traded, processed Atlantic cod. This will also contribute to a better understanding of past fluctuations in the sizes of cod individuals and populations.
Photo by Rachel Blevis
Clearly, the long and winding journey of Atlantic cod is far from over.
Obtaining new data on ancient cod exploitation is important for understanding our complex relationship with the seas and oceans.
Of late, consistent attempts to recover historical cod population numbers have increased. Nevertheless, wildlife conservation efforts have never been easily achieved. What might be the benefits of these efforts? This question leads to another:
When we think about oceans, do we think about the fish swimming in them as well? We are sure you agree, that an ocean with no fish is not really an ocean at all.
References
(1) Barrett, J.H., (2016). Medieval sea fishing, AD 500-1550: chronology, causes and consequences. In: Barrett, J.H., Orton, D. (eds.). Cod and herring, the archaeology and history of medieval sea fishing. Oxbow Books, Oxford.
(2) Bundy, A., Heymans, J., Morissette, L., and Savenkoff, C. (2009). Seals, Cod and Forage Fish: A Comparative Exploration of Variations in the Theme of Stock Collapse and Ecosystem Change in Northwest Atlantic Ecosystems. Progress In: Oceanography 81.
(3) Cod, British Sea Fishing, retrieved 28 Feb 2021 from:
(4) Christensen P, Nielseen A.R. (1996). Norwegian fisheries 1100-1970: main developments. In: The North Atlantic Fisheries, 1100-1976: National Perspectives on a common resource (eds. Holm P, Starkey DJ, Thor J). Esbjer: North Atlantic Fisheries Association. 145-176.
(5) Barrett, J.H., Orton, D., Johnstone, C., Harland, J., Van Neer, W., Ervynck, A., Roberts, C., Locker, A., Amundsen, C., Enghoff, I.B., Hamilton-Dyer, S. (2011). Interpreting the expansion of sea fishing in medieval Europe using stable isotope analysis of archaeological cod bones. Journal of Archaeological Science 38 (7). 1516-1524.
(6) Betts MW, Noël S, Tourigny E, Burns M, Pope PE, Cumbaa SL (2014). Zooarchaeology of the historic cod fishery in Newfoundland and Labrador, Canada. Journal of the North Atlantic. 24:1-21.
(7) Holm, P., Ludlow, F., Scherer, C., Travis, C., Allaire, B., Brito, C., Hayes, P.W., Al Matthews, J., Rankin, K.J., Breen, R.J. and Legg, R. (2019). The North Atlantic Fish Revolution (ca. AD 1500). Quaternary Research. 1-15.
(8) Rose, G.A. (2019). Exploitation: Cod is Fish and Fish is Cod. Wiley Blackwell. Vancouver, Canada. 397.
(9) Mitchell, K.J., and Rawlence, N.J. (2021). Examining Natural History through the Lens of Palaeogenomics. Trends in Ecology & Evolution 36(3). 258-267.
(10) Oosting, T., Star, B., Barrett, J.H., Wellenreuther, M., Ritchie, P.A., and Rawlence, N.J. (2019). Unlocking the potential of ancient fish DNA in the genomic era. Evolutionary Applications 12(8). 1513-1522.
(11) Wheeler, A., and Jones, A.K.G. (1989). Fishes. Cambridge Manuals in Archaeology. Cambridge University Press. 4-188.
(12) Enghoff, I. B.(1994). Fishing in Denmark during the Ertebølle Periodxs. International Journal of Osteoarchaeology 4, no. 2. 65–96.
(13) Jones, A.K.G. (1991). The Fish Remains from Freswick Links, Caithness. Phd, University of York.