Written by Dr Paul Montgomery Ph.D., Investigação Científica Faculdade de Arquitectura da Universidade do Porto, Portugal & Reserch Fellow Trinity College Dublin, Ireland
The point at which the land and water connect holds special significance for me. In my field, Archaeology, we refer to this as the intertidal zone. For nerds like me, this is recognised as one of the most important areas in the historical and archaeological record. From the earliest times, civilizations have chosen to utilise these intertidal areas for their strategic importance and access to the sea. Here, I will share with you my experiences of travelling the globe to study the ancient fishing technology found in the intertidal zone, technology that is still used today. This journey has taken me to Ireland, the UK, the Netherlands, Denmark, Spain, Portugal, China, and Taiwan. Through the study of stone fish weirs, rock formations designed to catch fish, I have unlocked secrets of our past relationship with the sea and uncovered ways to adapt to environmental pressures in the present and future. However, these formations are in danger of being lost, threatened by the ongoing erosion wrought by the climate crisis. In recounting my journey, I hope to inspire others to look to our past to help us understand the present and realise the value of preserving this ancient technology.
My initiation into the intertidal world did not come in university or in any academic setting. Rather, it began through my boyhood hobby of sea angling. This led to many hours spent wandering the intertidal zone of Dublin gathering different species of marine worms, shellfish, and crustaceans as bait. It's fair to say that my interest in academia, at the time, was somewhat limited by the fact that I was a poor student due to my undiagnosed dyslexia. During my early school years at the Presentation Brothers secondary school in Dublin, sea angling gave me the opportunity to travel extensively around Ireland and the British Isles to participate in fishing competitions. These experiences introduced me, inadvertently, to the intertidal archaeology of Ireland, such as on the Shannon estuary and Strangford Lough. Little did I know that my childhood hobby was shaping my future academic outlook.
After my dyslexia was properly diagnosed, I reflected on how archaeology is about incomplete stories that need to be investigated patiently and carefully, where incomplete data can resemble the nature of dyslexia at times.
My interest in history and archaeology, in particular in the maritime world, led me to study history, ancient literature, and archaeology at the University College Utrecht in the Netherlands at both the BA and MA levels. While investigating the coastal fortifications of the Peloponnese war (431–404 BC) in the Attic region around modern Athens and Greece, I investigated the maritime installations built on these sites, and their significance to the sea. These fortifications represented a crucial network of maritime trade along the coast all the way to the Black Sea, which provided a vital source of grain during the war with the Peloponnese forces. This research acted as a gateway into the world of maritime archaeology and fuelled my interest to delve further into the field.
Like all good scholars, I realised that I actually knew very little and needed to develop the skills required for deeper investigation in the field of maritime archaeology. So, I packed my bags and went to the Southern University of Denmark SDU, under the tutelage of the late Professor Thijs Jakob Maarleveld (21 October 1953–11 March 2021). This was a significant turning point for me in terms of the skills I acquired working on a number of shipwrecks in Denmark, Sweden, and the UK and which meant training as a commercial diver to investigate underwater cultural heritage. Working on a shipwreck means locating ancient artefacts which reveal important facts about how people traded and communicated in the past. I was beginning to realise the interconnectedness of natural and cultural impacts on the marine environment. Human actions leave traceable marks and delving into our history with the sea uncovers many forgotten lessons.
The next chapter in this Odyssey led to the muddied expanse of Lough Swilly’s intertidal zone in Co. Donegal, Ireland, and a PhD with the University of Ulster (UK). In the spring of 2011, while I was walking along the shores of the Lough, a V-shaped ripple appeared on the surface of the water as the tide ebbed. From an archaeological point of view, this was thrilling! The ripples grew into a line of stones silhouetting the V-shape structure in the water below and then a wall emerged as the tide dropped, and a fully visible stone fish weir that had not been used for three centuries appeared. This weir was to be one of six discovered here during a survey of the shoreline, dating from the Irish Medieval period (1150-1550 AD) to the early Modern period (1550–1850 AD) . The Lough had started to reveal its past to me. Though not unique or in any way spectacular, this discovery opened up a new window into maritime archaeology, further reinforcing my feeling that where the sea meets the land marks a special area of archaeological intrigue. Our relationship with the sea provides an important record of our past, insights into our evolution as Homo sapiens and prods us with difficult questions about how these historical records will disappear as a result of climate change.
Much of my current research has been shaped by the twin challenges of understanding the archaeological record in the intertidal zone and dealing with the challenges presented by climate change. While teaching in China at the Liaocheng University in Shandong Province, I had the opportunity to visit a number of archaeological sites where humans have fished and utilised the intertidal zone for thousands of years. These sites are now in danger of disappearing due to the imposing threat of sea level rise.
Around the world, many sites like these are under appreciated as they have neither the attraction of large imposing ancient structures, such as Stone Henge or the Great Pyramid of Giza, nor the possibility to become cultural centres making them economically valuable as tourist locations.
This represents a lost opportunity. These sites reveal that our cultural and economic development is rooted in our relationship with the sea and can encourage us to value and preserve our ancient oceanic bonds. They also offer insight into our historical resilience against climatic shifts and preserve ancient technology utilised for this purpose. A prime example is the continued use of stone tidal weirs by local and indigenous communities to feed themselves through non-invasive fishing methods. At a time of great uncertainty brought on by climate change, their approach illustrates how humans can work alongside nature, rather than against it, to sustain life. The escalating impact of the climate crisis serves as a call to governments to protect our past, which, like our stone fish weirs, is literally sinking into the sea.
Following my work in China, I travelled to Spain. The communities who manage the stone fish weirs of Andalusia, in Southern Spain, visit the sites of their fish traps daily not just to catch fish but to check the structures ensuring that the tides or storms haven't damaged them. It’s an exemplar of bottom-up conservation. While in Andalusia, I walked up and down the length of a three-kilometre stone fish weir to observe what was happening on the ground. I observed fishermen using differing repair methods to stabilise the wall and restore stone structures that had been washed away by storms. I was impressed by the level of attention and energy exerted by local people utilising the intertidal zone to maintain their livelihoods. Despite not being their primary source of income, many part-time fishermen use these fishing structures to feed their families as part of their domestic economy. The level of effort and attention required to maintain these monuments reflects their importance to these Spanish communities. The daily rhythms that I observed demonstrated the harmony between the movement of the tides and the necessity of season to fish and then repair in turn.
Intertidal zone conservation and research are in desperate need of funding. In the world of maritime archaeology, shipwrecks and tales of sunken treasure take centre stage, sucking up the media attention and funding. However, unlike nets or fishing hooks, fish weirs represent an imitation of the natural environment by humans. The development of fish weirs is truly astounding when we reflect on the fact that ancient communities, who lived in basic shelters and lacked the technology we boast of today, invested considerable effort in building life-sustaining 100-metre-long fish weirs. Through trial and error, they gained deeper understandings of the ebb and flow of the tides as well as the movements of fish species which they took advantage of to feed themselves. By copying nature, they were able to support their communities without denigrating their environment. Surely this is an important lesson for modern humans.
My appreciation for these lessons from our past has been reinforced by the opportunity to work with communities and my fellow scholars from UNESCO endorsed “Indigenous People, Traditional Ecological Knowledge, and Climate Change: The Iconic Underwater Cultural Heritage of Stone Tidal Weirs” project together on fish weirs and traps in Africa, Asia, and the Americas . For example, the indigenous communities of Micronesia have a complex and well-established cultural tradition around the use of their fish weirs. These communities, like many island populations of wider Asia Pacific, are vulnerable to the most extreme impacts of climate change, such as accelerated rising sea levels, drastic alteration of the local ecology, and acidification of the waters endangering their lives and livelihoods. The Yapese in Micronesia have a corpus of sacred traditional law governing the construction and use of these structures . Their belief systems are also highly attuned to the natural environment. Even their legends narrating the construction of the first fish weirs include instructions from ancestral spirits, some of whom are represented by natural avatars such as fish. Even today, the management of fish weirs is alive and flourishing. In their society the access and use of fish weirs are tightly controlled allowing for long periods of inactivity during which fish species have time to breed and regenerate resulting in a more diverse ecological environment . Their treatment of the natural environment, not just as a resource to exploit, but one to conserve and respect, underlines their close relationship with the maritime ecology of the area. Their day-to-day experiences offer us deeper insights into how humans lived in the past and how we may utilise some of this innate knowledge to address climate change challenges in the present.
The sea and tides have many lessons to teach us.
Despite the growth of commercial fishing, the use of fish weirs is resurging. Earlier this year, I had the opportunity to visit Taiwan and observe how communities have been reviving their use. Taiwan is home to one the largest concentrations of stone tidal fish weirs, and home to some of the most well-preserved examples of this architectural form . In particular, the area around Penghu Archipelago in the Strait of Taiwan is home to over 500 stone tidal fish weirs. The coastal communities, with support from government, are engaging in a movement to bring stone fish weirs back into use as a functioning part of the marine environment. Local communities are launching and spearheading initiatives, actively participating in the process of recovering both the physical and cultural knowledge of these structures. The goal is not to alter the entire economic landscape of fisheries in Taiwan. Instead, the focus is on revitalising this part of their cultural heritage. This represents not only a part of their cultural identity but also, a constructive way to catch fish and increase the marine richness of the ecology around the island. The intertidal zone and fish weirs represent the possibility to not only preserve our cultural heritage, but also reactivate an ancient relationship with our marine environment. In this world, we can still catch fish, but in a way that works in harmony with the natural flow of seas and does not damage the wider marine environment.
Ultimately, many of the questions I posed here are only in the process of being answered as we dig deeper and deeper into the complex relationship between human communities and their use of the intertidal zone through fish weirs. There are some who might consider this to be an unwarranted question to spend so much time considering. However, the story of the past is always one we can learn from, but only if we're willing to be honest about the values that we hold to be important. The climate crisis has forced us to reflect on whether our endless economic growth is desirable, and serves as a reminder that we can never ignore the sea.
 Montgomery P, Forsythe W, Breen C. Intertidal fish traps from Ireland: Some recent discoveries in lough swilly, co. Donegal. J Marit Archaeol. 2015;10(2):117-139. doi:10.1007/s11457-015-9146-z. Montgomery P, “At the ebb of the tide: Exploring the Cultural Heritage of Stone Tidal Weirs”. https://www.tcd.ie/tceh/blogs/paul.php Accessed on 13/07/2023  INDIGENOUS PEOPLE, TRADITIONAL ECOLOGICAL KNOWLEDGE, AND CLIMATE CHANGE: THE ICONIC UNDERWATER CULTURAL HERITAGE OF STONE TIDAL WEIRS: https://www.oceandecade.org/actions/indigenous-people-traditional-ecological-knowledge-and-climate-change-the-iconic-underwater-cultural-heritage-of-stone-tidal-weirs/ . Accessed on 22/09/2022.  Jeffery B, Pitmag W. The aech of Yap: a survey of sites and their histories. Yap State Historic Preservation Office; 2010.  Jeffery B. Reviving community spirit: furthering the sustainable, historical and economic role of fish weirs and traps. Journal of Maritime Archaeology. 2013 Jun;8:29-57.  Zayas, N. Cynthia. "Describing stewardship of the common sea among Atob fishers of the Pacific Rim Islands: cases from the Philippines, Taiwan and Japan." 南太平洋研究= South Pacific Study 31, no. 2 (2011): 71-80.