Introduction
The Mekong Delta constitutes a complex socio-ecological system of strategic importance to Viet Nam’s national food security and economic development. In recent decades, the region’s increasing vulnerability has highlighted the urgent need for locally grounded adaptive mechanisms, particularly in coastal areas that have long been closely associated with fishing-based livelihoods. The coastal zone of the Mekong Delta extends across seven coastal provinces Tiền Giang, Bến Tre, Trà Vinh, Sóc Trăng, Bạc Liêu, Cà Mau, and Kiên Giang bordering both the East Sea and the Southwestern Sea, with a total coastline of approximately 732 km. Offshore, this maritime area encompasses numerous islands and archipelagos, including Hòn Đá Bạc, Hòn Khoai, Hòn Chuối, the Nam Du Archipelago, the Bà Lụa Archipelago, the Hải Tặc Archipelago, the An Thới Archipelago, and the Thổ Chu Archipelago. This region is widely recognized as one of the country’s most dynamic and rapidly developing fisheries zones, owing to its extensive fishing grounds, warm seawater, shallow continental shelf, and vast marine area. The coastal waters of the Mekong Delta are characterized by abundant and diverse marine resources, including pelagic, demersal, and deep-sea fish stocks. The total estimated marine and aquatic resource reserve reaches 439,992 tons, with an exploitable yield of approximately 207,597 tons (Tran and Pham, 2014). Over the past century, these favorable natural conditions have facilitated the formation and gradual expansion of numerous fishing communities, evolving from nearshore and coastal exploitation to offshore fishing activities. Prominent fishing localities in the Mekong Delta include Vàm Láng town (Gò Công Đông district, Tiền Giang province), Bình Thắng commune and An Thủy commune (Bình Đại and Ba Tri districts, Bến Tre province), Đại An town (Trà Cú district, Trà Vinh province), Trần Đề town (Trần Đề district, Sóc Trăng province), Gành Hào town (Đông Hải district, Bạc Liêu province), Sông Đốc town and Cái Đôi Vàm town (Trần Văn Thời and Phú Tân districts, Cà Mau province), among others. In addition, many fishing households reside on offshore islands and archipelagos, relying almost exclusively on fishing for their livelihoods and survival. At present, coastal fishing communities in the Mekong Delta are confronted with multiple and intensifying challenges. Increasingly erratic weather patterns particularly storms in the East Sea combined with sea-level rise have exerted severe impacts on both livelihoods and daily living conditions. Declining fish stocks have resulted in mounting economic losses for fishers, often rendering offshore fishing trips financially unviable. In some cases, these pressures have driven fishing vessels to cross into the maritime zones of neighboring countries, leading to vessel seizures and the confiscation of assets. The case of the Sông Đốc fishing community one of the largest fishing centers in the Mekong Delta illustrates these challenges clearly. Although offshore fishing vessels are now equipped with more advanced technologies than in the past, fishing activities remain highly dependent on unpredictable natural conditions. Fishers operating at sea are directly exposed to rough waves, strong winds, and sudden storms, with the greatest danger arising when typhoons strike while vessels are still far offshore and unable to reach safe shelters in time, posing serious threats to human life. Moreover, in recent years, fishing yields have shown a declining trend due to the gradual depletion of marine resources, thereby intensifying livelihood pressures on fishing households. The growing number of vessels from different provinces operating in the Southwestern Sea has further increased the risk of overexploitation of marine resources that were once abundant. The widespread use of modern navigation and fish-finding technologies enables vessels to locate and harvest entire fish schools with high efficiency, including juvenile fish, leaving little opportunity for natural regeneration. This practice poses significant risks to the short- and long-term sustainability of fisheries in Sông Đốc and the wider Mekong Delta region (Duong, 2019). In this context, coping with increasingly frequent and unpredictable storms and natural hazards has emerged as an urgent concern for coastal fishing communities in the Mekong Delta today.
Against the backdrop of persistent exposure to storms that directly disrupt fishing activities, this study focuses on the role of Indigenous Knowledge (IK) within coastal fishing communities in the Mekong Delta, Viet Nam, in the context of socio-ecological adaptation. This issue carries both urgent academic and practical significance, as the resilience of coastal communities depends not only on externally driven technological or institutional interventions, but also on their capacity to mobilize inherited knowledge systems to sustain livelihoods under the dual pressures of climate change and resource depletion. The urgency of investigating fishers’ indigenous knowledge stems from the convergence of two major socio-ecological threats: the rapid decline of marine living resources and the increasingly pervasive impacts of climate change. First, climate change places fishing communities on the frontline of risk exposure. They are among the earliest and most severely affected groups, confronting sea-level rise, more frequent and intense flooding, and the growing destructive force of storms. These processes have directly undermined fishing infrastructure, production assets, and the viability of livelihood planning among coastal fishers. Second, nearshore marine resources have been experiencing a severe and alarming decline, often described as approaching a critical threshold of collapse. High-value and economically important species have largely disappeared from coastal waters, leaving predominantly low-value and juvenile fish stocks. The primary driver of this depletion is overexploitation, with fishing intensity far exceeding the maximum sustainable yield. Of particular concern is the emergence of a profound socio-ecological paradox. While marine resources continue to diminish, the number of nearshore fishing vessels has steadily increased. This phenomenon can be attributed to economic pressure: for many poor fishing households, fishing remains the sole viable source of livelihood, and financial constraints limit their ability to operate offshore. Poverty and resource decline thus interact to generate a negative feedback mechanism, compelling fishers to adopt increasingly intensive and in some cases destructive fishing practices in an attempt to maintain catch volumes. The proliferation of small-scale vessels and the use of destructive fishing methods not only accelerate resource degradation but also erode the ecological foundations upon which traditional management knowledge is built. As these knowledge systems lose their material and environmental bases, fishing communities become trapped in a self-reinforcing cycle of vulnerability and ecological degradation that is increasingly difficult to escape.
Indigenous knowledge continues to hold significant value and relevance for the survival and development of contemporary communities. In the 1990s, the World Bank underscored the importance of indigenous knowledge, defining it as a fundamental basis for decision-making across all domains of modern life, including natural resource management, nutrition and food security, healthcare, education, and social and community activities. Indigenous knowledge also provides locally grounded strategies for addressing the challenges faced by local communities (Ngo and Huynh, 2017). Indigenous knowledge among coastal fishing communities represents a multidimensional field of inquiry, encompassing systems of knowledge, practices, and resource management processes that have been developed and transmitted across generations. A growing body of research demonstrates that indigenous knowledge plays a crucial role in the sustainable management of coastal and marine resources, while simultaneously enhancing the capacity of local communities to adapt to environmental change and climate variability (Ensor, 2025; Thoral et al., 2025).A core component of indigenous knowledge lies in the deep understanding of marine ecosystems and their interactions with the ecological, economic, and cultural dimensions of indigenous communities. Empirical studies indicate that indigenous knowledge enables communities to implement effective resource management practices, ranging from fishing activities to the conservation of coral reef ecosystems (Thomassin et al., 2010; Kadir et al., 2021). For instance, within the Tobati-Enggros fishing community in Papua, local knowledge extends beyond practical expertise in marine resources to encompass culturally embedded norms and customary rules governing marine management (Kadir et al., 2021). This case illustrates that indigenous knowledge should be understood not merely as an accumulation of information, but as a system of values, norms, and social responsibilities. Moreover, the integration of indigenous knowledge with modern scientific approaches has been shown to be an effective strategy for resource management and ecological conservation. Studies suggest that the meaningful participation of local communities in research and management processes not only enhances data quality but also fosters trust and mutual collaboration between researchers and community members (Adams et al., 2014; Rivers et al., 2023). Such integrative approaches contribute not only to ecosystem resilience but also to the establishment and maintenance of long-term, trust-based relationships among stakeholders (Adams et al., 2014). Despite its recognized value, the incorporation of indigenous knowledge into policy-making and resource governance remains fraught with challenges, including insufficient recognition and valuation of local knowledge within formal policy and decision-making frameworks (Rivers et al., 2023; Rojas et al., 2025). The inherent complexity of socio-ecological systems requires governance approaches that attend not only to ecological dimensions but also to cultural values and indigenous knowledge systems (Loring, 2012). In Viet Nam, indigenous knowledge among coastal fishing communities has been examined by scholars in ethnology and cultural studies. Notable contributions include those by Ngô Đức Thịnh and colleagues (2000), Phan Thị Yến Tuyết (2014), Nguyễn Chí Bền (2019), Dương Hoàng Lộc (2020),· · · These studies conceptualize indigenous knowledge as a cultural component of fishing communities, preserved and transmitted across generations, providing critical insights into hydrological patterns and weather conditions that enable fishers to anticipate and mitigate natural hazards during fishing activities, as well as to understand the reproductive cycles and behavioral patterns of marine species that support effective harvesting (Ngo et al., 2000).Furthermore, indigenous knowledge is widely recognized as a valuable cultural asset that warrants preservation and revitalization, particularly in the context of increasingly erratic climatic conditions in Viet Nam, where such knowledge remains essential to contemporary fisheries (Nguyen, 2019). Other studies emphasize that indigenous knowledge among fishers represents a long-term adaptive process grounded in experiential engagement with the marine environment, reflecting profound ecological understanding and respect developed through continuous interaction between communities and their ecosystems (Duong, 2020). This knowledge plays a vital role in sustaining resource-based livelihoods among coastal fishing communities in Viet Nam. In summary, indigenous knowledge among coastal fishing communities constitutes not only a valuable resource for sustainable marine resource management but also a critical factor in enhancing local adaptation to environmental challenges. Recognizing and integrating this knowledge into resource governance and policy frameworks can contribute substantially to the protection of marine ecosystems and the sustainability of coastal livelihoods.
At present, the indigenous knowledge of coastal fishing communities plays a critical role in enabling adaptation to the ecological changes they face. This body of knowledge, commonly referred to as Traditional Ecological Knowledge (TEK), encompasses not only practical techniques but also constitutes an integral component of community culture and identity (Ruíz-Mallén and Corbera, 2013; Drew, 2005). Transmitted across generations, TEK enables communities to develop a nuanced understanding of the relationships between humans and their surrounding environments, thereby enhancing resilience and adaptive capacity under changing environmental conditions (Berkes et al., 2000; Gómez-Baggethun et al., 2012). A substantial body of literature demonstrates that integrating indigenous knowledge into resource management strategies can significantly strengthen community adaptation to climate change and to broader socio-ecological pressures (Alberio and Soubirou, 2022; Cinner et al., 2018). For example, the application of TEK in fisheries management has been shown to markedly improve adaptive strategies among coastal communities in Kiribati and Vanuatu by providing participatory insights into ecological and economic dynamics (Campbell et al., 2024). When fishers possess detailed knowledge of fish migration patterns and other ecological processes, they are better positioned to make proactive decisions regarding the timing and location of fishing activities, thereby mitigating the impacts of environmental variability. Moreover, the use of TEK has proven effective in the development of community-based management interventions, fostering stronger linkages between resource managers and fishing communities (Lipsman, 2019). In Québec, for instance, coastal communities have adopted cooperative management approaches grounded in indigenous knowledge to enhance resilience in the context of global environmental change (Alberio and Soubirou, 2022). Such models not only contribute to resource conservation but also facilitate the revitalization of traditional values and customary practices, while remaining aligned with contemporary governance frameworks. Indigenous knowledge further supports the establishment of early-warning systems and information-sharing platforms that enable fishers to prioritize sustainable resource management (Campbell et al., 2024; Montgomery and Vaughan, 2018). Research on fishing communities thus spans from investigations of local ecological knowledge to analyses of climate change impacts, with the overarching objective of strengthening the resilience of socio-ecological systems and reducing adverse effects on fishers’ livelihoods (Galappaththi et al., 2019). The integration of TEK with modern scientific knowledge forms a comprehensive management approach that enhances sustainability and overall community resilience (Galappaththi et al., 2019; Bennett et al., 2014). Ultimately, the recognition and formal incorporation of indigenous knowledge into official management frameworks are essential to ensure that such knowledge is not marginalized within sustainable development policies and planning processes. The contributions of fishers extend beyond economic value to encompass social and cultural dimensions, which merit careful consideration in the context of modernization and environmental degradation (Gómez-Baggethun et al., 2012; Kyvelou et al., 2023). In summary, indigenous knowledge among coastal fishing communities can be regarded as a key pillar in building adaptive capacity in response to ecological change. Integrating this knowledge into resource governance offers long-term benefits for both communities and marine environments.
Taken together, the foregoing analysis indicates that the indigenous knowledge of coastal fishing communities in the Mekong Delta represents not only a cultural heritage accumulated over generations but also a practical ecological knowledge system of particular relevance under contemporary conditions of climate change and resource depletion. As marine ecosystems face unprecedented pressures from sea-level rise and salinity intrusion to increasingly intense storms and rapid depletion of fish stocks this knowledge provides a critical foundation for risk anticipation, adaptive adjustment of fishing strategies, and the flexible maintenance of livelihoods. However, the degradation of resource bases and ongoing socio-ecological transformations pose serious risks to the continuity and intergenerational transmission of indigenous knowledge, underscoring the need for in-depth research to better understand the limits, transformations, and adaptive potential of these knowledge systems. Accordingly, the study of indigenous knowledge among fishing communities in the Mekong Delta holds both theoretical significance, by elucidating mechanisms of human-environment interaction within complex socio-ecological systems, and pressing practical value for policy formulation, resource governance, and sustainable livelihood development. In a context where modern technical and managerial solutions remain insufficient to fully address climatic and environmental uncertainties, the identification, revitalization, and integration of indigenous knowledge into fisheries governance and coastal management emerge as strategic imperatives. This study therefore seeks to fill an important knowledge gap while providing a scientific basis for policies aimed at enhancing the resilience and adaptive capacity of coastal fishing communities in the Mekong Delta during a period of profound environmental change.
Despite the growing recognition of indigenous knowledge as a critical component of socio-ecological adaptation, existing studies on coastal fishing communities in the Mekong Delta remain largely descriptive and fragmented. There is still limited empirical work that systematically examines how different domains of indigenous knowledge operate as adaptive mechanisms within specific ecological contexts, how such knowledge varies across distinct marine environments, and how it is being transformed under the combined pressures of climate change, resource depletion, and technological modernization. In particular, few studies explicitly engage with the concept of the "cultural core" to distinguish between forms of indigenous knowledge that remain essential to subsistence and economic organization and those that are increasingly weakened or displaced. Addressing these gaps, this study formulates the following research questions. Accordingly, this study is guided by the following research questions: (1) How is indigenous ecological knowledge mobilized by coastal fishers in An Thủy and Sông Đốc to adapt to climate change and marine resource depletion in everyday fishing practices? (2) Which forms of indigenous knowledge can be regarded as a "cultural core," playing a pivotal role in sustaining fishing-based livelihoods and economic organization within these communities?
Research Methods
Theoretical Research Approach
Julian Steward’s theory of cultural ecology, widely regarded as one of the foundational pillars of modern anthropology, focuses on the interrelationship between culture and the ecological environment in which human societies exist. Steward argued that culture and ecology constitute an integrated whole, in which the survival and development of any given culture depend fundamentally on specific ecological conditions (Halder and Zheng, 2023; Sadowski, 2007). According to this perspective, environmental changes inevitably lead to corresponding transformations in modes of subsistence, patterns of behavior, and forms of social organization within communities (Sadowski, 2007). Steward introduced the concept of the "cultural core," emphasizing that those cultural elements essential to a community’s survival emerge directly from sustained interaction with the natural environment (Waluya et al., 2023). This aspect of cultural ecology helps explain how communities adapt to ecological conditions and develop sustainable livelihood strategies in response to environmental constraints and opportunities. His empirical studies of small-scale societies demonstrated that discernible regularities exist in how different cultures organize their ways of life according to the abundance or scarcity of surrounding resources (Halder and Zheng, 2023; Sadowski, 2007). In his seminal work Theory of Culture Change (1955), Steward conceptualized culture as comprising three interrelated systems biological, social, and cultural thereby underscoring their reciprocal relationships (Pandey, 2022; Diener, 1980). Fundamentally, he argued that a proper understanding of cultural development requires careful attention to the ways in which ecological conditions shape social practices and organizational forms within human communities. Steward also placed particular emphasis on the development of collaborative research approaches between scholars and local communities, enabling cultural and ecological dimensions to be examined and preserved through systematic fieldwork (Wenzel, 1999). Such approaches not only illuminate how communities adapt to environmental change but also highlight the potential of locally embedded knowledge systems commonly referred to as Traditional Ecological Knowledge (TEK) held by these communities (Wenzel, 1999).
A key contribution of Steward’s cultural ecology lies in its emphasis on adaptive capacity, suggesting that communities evolve over time through the dynamic integration of cultural practices, environmental conditions, and economic factors (De, 2024). His framework has influenced a wide range of disciplines, including political ecology, where scholars increasingly recognize the critical role of socio-cultural factors in addressing contemporary environmental challenges (Slocombe, 1993).
In summary, Julian Steward’s theory of cultural ecology offers a critical perspective on the relationship between humans and their environments, emphasizing that cultural persistence and transformation cannot be separated from the ecological contexts in which they arise. By integrating cultural and ecological concepts, Steward not only provided anthropology with a rigorous analytical framework but also laid the groundwork for subsequent research on sustainable development and cultural adaptation in the face of environmental change.
Research Methodology
This study employs two primary data sources: secondary data and primary data. Secondary data were collected from multiple sources, including libraries and archival materials. Primary data were gathered through participant observation and in-depth interviews conducted in two representative coastal fishing communities in the Mekong Delta: An Thủy commune ( Ba Tri district, Bến Tre province) and Sông Đốc town (Trần Văn Thời district, Cà Mau province). Fieldwork in these two localities was carried out intermittently over an extended period from 2018 to 2023, involving multiple rounds of site visits and field surveys. Both An Thủy commune and Sông Đốc town are closely associated with the historical formation and development of coastal and offshore fisheries in the Mekong Delta. In 2020, An Thủy commune located near the Hàm Luông River estuary had approximately 960 fishing vessels, employing around 7,000 workers. Meanwhile, Sông Đốc, situated at the mouth of Sông Đốc estuary along the southwestern coast, has developed into a bustling fishing town attracting vessels from various provinces that operate in the Southwestern Sea. In 2020, the town recorded 1,373 fishing vessels and supported tens of thousands of fishers engaged in offshore fishing activities. These two sites represent typical open-coast (bãi ngang) fishing communities, with a continuous history of marine exploitation spanning nearly a century. Owing to their long engagement in fishing activities and accumulated experiential knowledge, indigenous knowledge systems among fishers in these communities are particularly rich and diverse. The selection of An Thủy (Ba Tri, Bến Tre) and Sông Đốc (Trần Văn Thời, Cà Mau) was motivated not only by their representativeness in the historical development of nearshore and offshore fisheries in the Mekong Delta, but also by a clear scientific objective: to identify differences in hydrological and weather-related indigenous knowledge across two marine ecological zones characterized by contrasting natural conditions. An Thủy is associated with the Hàm Luông estuary, where semi-diurnal tidal regimes prevail, salinity fluctuates strongly across seasons, and ecological dynamics are directly influenced by the East Sea. In contrast, Sông Đốc is located along the western coast, where fishing activities are shaped by the Southwest monsoon and a predominantly diurnal tidal regime. These distinct ecological contexts generate different maritime practices and, consequently, distinct indigenous knowledge systems related to weather forecasting, sea observation, tidal cycles, and fish behavior. Studying these two communities in parallel therefore enables not only an in-depth understanding of how fishers accumulate and apply indigenous knowledge under specific ecological conditions, but also a comparative analysis to identify shared patterns and contextual differences in environmental adaptation strategies across coastal regions. This comparative approach contributes to a deeper understanding of the culture-ecology relationship in line with Julian Steward’s cultural ecology framework, while highlighting the value of indigenous knowledge as a critical form of capital that enables communities to respond effectively to environmental variability and uncertainty.
In-depth Interviews
In-depth interviews were conducted to collect qualitative data on indigenous knowledge systems as they have evolved over time. The study employed a purposive sampling strategy combined with convenience sampling to ensure representativeness while avoiding rigid constraints on sample size. In total, 30 informants from An Thủy commune and Sông Đốc town were interviewed. Selection criteria included age, gender, and diversity of fishing experience in order to capture a broad spectrum of community knowledge. Interviewees included both men and women aged 18 and above, with individuals in the 50–70 age group constituting a significant proportion of the sample, as they tend to possess extensive indigenous knowledge as well as deep familiarity with the historical and cultural context of local fisheries. Retrospective interviews with elderly fishers provided rich insights into indigenous knowledge in relation to ecological conditions, highlighting its critical role in local fishing practices and livelihood strategies.
Participant Observation
Participant observation was employed to complement the interview data and to deepen understanding of indigenous knowledge in relation to livelihoods and the natural environment. The research team directly participated in and observed various activities under the guidance of experienced fishers, including monitoring hydrological patterns, weather conditions, and fish species caught during fishing trips. Through these activities, the researchers gained insights into how fishers interpret environmental signals to predict weather changes and identify spawning grounds in both nearshore and offshore areas. Observations were conducted at different times of the year to capture seasonal variability, thereby providing a comprehensive view of indigenous knowledge in relation to local ecological conditions. All data collected through interviews and observations were carefully recorded, systematically archived, and synthesized into detailed field diaries to support subsequent analysis and reporting.
All qualitative data collected through in-depth interviews and long-term participant observation were analyzed using an iterative thematic analysis approach. Field notes, interview transcripts, and observational records were first systematically organized and coded to identify recurring patterns related to indigenous ecological knowledge, livelihood practices, and environmental adaptation. Initial open coding focused on empirical categories emerging directly from the data, such as weather forecasting, tidal interpretation, navigation cues, species-seasonality knowledge, and risk avoidance practices. These inductive codes were subsequently refined and grouped into higher-order analytical themes corresponding to two core domains: (i) knowledge related to hydrology and weather, and (ii) knowledge related to marine living resources. In a second analytical stage, the identified themes were interpreted through the theoretical lens of cultural ecology, with particular reference to Julian Steward’s concept of the "cultural core." This stage involved distinguishing forms of indigenous knowledge that remain closely tied to subsistence activities and fishing-based economic organization from those that have been weakened, transformed, or partially displaced under conditions of ecological change and technological modernization. Comparative analysis between An Thủy commune and Sông Đốc town was conducted to examine how variations in tidal regimes, monsoon patterns, and marine ecological conditions shape differences in knowledge systems and adaptive strategies across the two communities. Throughout the analysis, attention was paid to both continuity and change in indigenous knowledge, emphasizing its dynamic and adaptive character rather than treating it as a static body of tradition. Ethical considerations were integral to all stages of the research process, particularly given the extended duration of participant observation from 2018 to 2023. Prior to data collection, verbal informed consent was obtained from all participants, who were fully informed about the aims of the study, the voluntary nature of their participation, and their right to withdraw at any time. To protect confidentiality, personal identifiers were removed from all records, and pseudonyms were used where individual narratives are referenced. Long-term engagement with the communities allowed for the development of trust-based relationships, which helped minimize extractive research practices and ensured that observations were conducted in a respectful and culturally appropriate manner. The researcher adhered to ethical principles of non-interference, reciprocity, and reflexivity, remaining attentive to power relations and the potential impacts of prolonged observation on everyday community life.
Results and Discussion
To evaluate and classify fishers’ indigenous knowledge in a systematic and scientific manner, this study draws on the classification frameworks proposed by Ngô Đức Thịnh and colleagues (2000) and Phan Thị Yến Tuyết (2014). Ngô Đức Thịnh and colleagues (2000) categorize the folk knowledge of fishing village communities into three main types: (i) knowledge and experience related to weather conditions (including winds, storms, and tidal movements); (ii) knowledge of fish and shrimp resources; and (iii) knowledge of fishing techniques. Focusing on coastal areas in southern Viet Nam, Phan Thị Yến Tuyết (2014) provides a more detailed classification of fishers’ indigenous knowledge, including: indigenous knowledge of natural signs used to anticipate weather conditions at sea (such as observing the sky, stars, lightning, clouds, the moon, winds, seawater, waves, fish behavior, and seabirds); experiential knowledge of storm avoidance when vessels are offshore; indigenous knowledge related to fishing practices in southern coastal waters (including fish harvesting techniques and species identification); knowledge associated with specialized fishing practices such as lưới lặn (diving nets) and "listening to fish sounds underwater"; and indigenous knowledge of healthcare and healing practices in marine environments. Based on empirical data collected from the two fishing communities of An Thủy commune and Sông Đốc town, this study classifies fishers’ indigenous knowledge into two overarching categories: (i) knowledge related to hydrology and weather, and (ii) knowledge related to marine living resources. Broadly speaking, these forms of knowledge represent experiential understandings accumulated through long-term engagement in fishing activities, while also reflecting processes of adaptation to the specific ecological environments in which these communities are embedded and upon which their survival and development depend.
Knowledge related to Hydrology and Weather
Fishing as a livelihood necessarily requires vessels to operate at sea, and the farther offshore fishers travel, the greater the potential harvest of marine resources compared to nearshore waters. Consequently, over a long period of engagement with marine environments, Vietnamese fishers in the Mekong Delta have accumulated a substantial body of indigenous knowledge related to hydrology and weather conditions in both the southeastern waters of the East Sea and the offshore areas of the Southwestern Sea. This knowledge plays a crucial role in enabling fishers to recognize and anticipate weather conditions, thereby allowing them to plan and organize their daily fishing activities more proactively.
Indigenous knowledge related to hydrology and weather encompasses several interrelated components, including knowledge of monsoon wind systems, tidal regimes, and marine storms. These forms of knowledge are regarded as essential by experienced fishers, providing them with confidence and practical guidance when operating at sea. With respect to monsoon winds in the East Sea and the Southwestern Sea, generations of fishers have identified two dominant seasonal wind regimes: the southern monsoon and the northern monsoon (locally known as gió chướng). The cyclical patterns of these wind systems exert a strong influence on how fishing activities are organized among Mekong Delta fishers. The northern monsoon typically prevails from the tenth to the third lunar month, while the southern monsoon dominates from approximately the fourth to the ninth lunar month. During the northern monsoon season, fishers in An Thủy commune as well as other fishing communities operating in the East Sea tend to exercise particular caution. This period, extending roughly from the ninth to the twelfth lunar month, is associated with rough offshore seas, frequent storms, colder weather, and reduced availability of fish and shrimp. As a result, fishing during this season is considered highly challenging and potentially dangerous to both property and human life. Many nearshore fishers refrain from going to sea altogether, as weather conditions are deemed unsuitable for safe fishing operations. In contrast, fishing activities in the Southwestern Sea particularly among fishers in Sông Đốc town are generally more favorable during the northern monsoon season. In Sông Đốc, small-scale fishing vessels are highly dependent on monsoon wind patterns, and nearshore fishing is most viable during the northern monsoon months, from approximately the ninth to the third lunar month. During this period, sea conditions are relatively calm, with gentle waves and minimal strong winds, creating favorable conditions for fishing using various types of vessels and gear. Moreover, marine resources, especially shrimp and fish, are believed to reproduce more actively during this season. Consequently, many fishers begin preparing for offshore fishing as early as the end of the eighth lunar month. By contrast, during the southern monsoon season, fishing activities are often suspended due to the presence of strong and turbulent offshore waves, which may reach heights of four to five meters, severely constraining fishing operations. Knowledge of monsoon wind dynamics in the Southwestern Sea has been condensed by Sông Đốc fishers into a set of locally transmitted proverbs, such as: "Đông già bà chướng" (the end of the southeastern monsoon signals the onset of the northern monsoon), "Tắt bấc thổi nam, tắt nồm thổi chướng" (the cessation of the northern monsoon marks the beginning of the southern monsoon, and vice versa), and "Gió bấc thì hanh, gió nồm thì ẩm" (northern winds bring cool, dry weather, while southern winds bring humidity and storms) (DVT., male, 73 years old, Sông Đốc town, August 2022). Conversely, among fishers in An Thủy commune operating in the East Sea, the third lunar month is considered the most favorable time for fishing. This belief is captured in the saying "Tháng ba bà già đi biển" ( "In the third lunar month, even elderly women can go to sea"). According to local interpretations, the third lunar month also referred to as "mùa đồng chung" represents a transitional period between the northern and southern monsoons, characterized by calm and mild weather conditions. As a result, fishers actively engage in fishing activities during this time. In addition, fishers rely on subtle atmospheric cues to anticipate hazardous weather. For example, the appearance of gió heo may (a cool early-season wind) is interpreted as a warning sign of impending heavy rain, strong winds, or even storms, as reflected in local sayings such as "Gió heo may chẳng mưa dầm thì bão giật" ("If the heo may wind does not bring prolonged rain, it will bring violent storms") and "Gió may quay nồm" ("When the heo may wind shifts toward the southern monsoon, storms may follow") (NVD., male, 65 years old, An Thủy commune, May 2019).
Fishers’ knowledge of tidal dynamics is of critical importance, as tidal fluctuations directly shape the organization and execution of their daily fishing activities. In many coastal localities, fishing communities are settled inland near major river mouths, and their fishing vessels depend heavily on tidal cycles to navigate rivers and estuaries when departing for offshore fishing grounds or returning to anchorages. According to the geographer Lê Bá Thảo (1977), tidal regimes along the southwestern coast of Viet Nam differ markedly between the East Sea and the Southwestern Sea. Along the East Sea coast, tides follow a semi-diurnal regime, with two high and two low tides occurring each day. In contrast, the Southwestern Sea is characterized by a diurnal tidal regime, in which water levels rise and fall once per day. Lê Bá Thảo further notes that river systems in southern Viet Nam experience at least two tidal phases daily nước lớn (high tide) and nước ròng (low tide). During the full moon and new moon (the fifteenth and thirtieth days of the lunar month), tidal amplitudes are significantly higher than usual, causing noticeable turbulence across river surfaces due to intensified tidal movement. In the Rạch Giá-Hà Tiên Gulf, however, tidal fluctuations occur only once per day. Tidal forces not only affect water levels in rivers and canals throughout the Mekong Delta but also induce periodic reversals in river flow direction (pp. 245). As a result, fishers in the Southwestern region possess a sophisticated understanding of tidal regimes, enabling them to install fixed fishing gear (đáy) for shrimp and fish harvesting, as well as to time vessel departures and arrivals for safe navigation and anchorage. Beyond daily tidal cycles, fishers are also well versed in the fortnightly tidal rhythm. High tides are referred to as nước lớn, while low tides are known as nước ròng, with a vertical difference between the two typically ranging from approximately 2.5 to 3.5 meters. Particularly during the mid-lunar month specifically on the fifteenth day—fishers identify the tide as "con nước chánh" or "con nước cường", indicating a period when water levels rise higher than on other days. Based on this reference point, fishers are able to calculate daily tidal variations with remarkable precision, including the exact timing of peak high tides and lowest ebb tides. In An Thủy commune (Ba Tri district, Bến Tre province), many fishers reported that on the fifteenth and thirtieth days of the lunar month, water levels in the Hàm Luông River reach their highest points around midday (12:00) and midnight (24:00). During the northern monsoon season (gió chướng), stronger winds and waves often cause a phenomenon locally known as "nước nhảy", in which water levels surge and overflow riverbanks by approximately 0.5 to 0.7 meters. By contrast, throughout the southern monsoon season, water levels remain lower and less extreme than during the northern monsoon. Using these temporal markers, local fishers are able to calculate the timing of peak tides on subsequent days, noting that the occurrence of the daily highest tide is delayed by approximately one hour each successive day. Similarly, at the Ông Đốc estuary, fishers possess detailed knowledge that the fifteenth and thirtieth days of the lunar month correspond to the highest tides, with peak water levels typically occurring around midnight (24:00) before gradually receding. In the days that follow, the "con nước chánh" the daily maximum tidal level shifts later by roughly one hour each day. Notably, during the southern monsoon season combined with intense thunderstorms, particularly in the fourth, fifth, and sixth lunar months, exceptionally high tides (triều cường) and "nước nhảy" events frequently occur, leading to flooding of residential areas along rivers and canals in the region (DVT, male, 73 years old, Sông Đốc town, August 2022).
Fishermen’s experiential knowledge related to rainfall, storms, and typhoons plays a crucial role in their offshore voyages. Such knowledge enables them to anticipate rapid weather changes, particularly two decades ago, when fishing vessels were not yet equipped with modern communication technologies that could facilitate timely sheltering or emergency assistance. Ngô Đức Thịnh and colleagues (2000) emphasize that such experiences not only secure fishermen’s livelihoods but also serve as vital safeguards that help them survive life-threatening dangers posed by storms at sea (p. 65). This body of knowledge is transmitted by experienced fishermen in the Mekong Delta, including those from An Thủy and Sông Đốc, to younger fishermen, guiding them in interpreting natural phenomena in order to respond promptly to storms. For fishermen preparing to set sail or already at sea, the sight of flocks of birds especially swallows and seagulls flying hastily toward the shore is commonly interpreted as a sign that a storm will strike within the following day. Many fishermen also recount that the sudden appearance of cá mặt quỉ surfacing indicates imminent rough seas in the days ahead; consequently, this species is avoided and not harvested. In addition, some fishermen assert the saying "động nước trước động trời" meaning that continuous bubbling on the sea surface signals rising waves accompanied by approaching storms. Alongside observations of sea conditions, fishermen also rely on cloud formations and celestial bodies to forecast storm activity. The appearance of dark clouds in the sky is often considered reassuring, as it suggests heavy rainfall that will dissipate quickly, whereas dull gray clouds drifting overhead raise concerns about prolonged rainfall lasting several days. In An Thủy commune, this perception is expressed in a local folk verse:
When at sea, fishermen who carefully observe the stars can also anticipate the next day’s weather conditions, as reflected in the proverb: "Đông sao thì nắng, vắng sao thì mưa" (when many stars appear in the sky, the following day is likely to be sunny; conversely, sparse or absent stars indicate heavy rain) (TTB, female, 57 years old, An Thủy commune, October 2018).
In addition, experienced seafarers consistently pay close attention to celestial bodies. The sao cá liệt is considered particularly important for accurately determining navigation routes either offshore or back toward the shore. Fishermen therefore steer their vessels beneath this star to ensure a safe return, especially on dark nights. Many fishermen recount that when fishing offshore at night, elders relied on sao mai, sao hôm, and sao cày to determine the direction back to land. Sao mai typically rises around two or three o’clock in the morning; thus, if the helmsman observes the star aligned directly behind the stern, the vessel can be steered safely toward the shore. Similarly, the sao cày constellation consists of three stars aligned diagonally in a straight line resembling a plough blade and also rises around two or three o’clock in the morning. By steering the vessel along the direction of this constellation, fishermen can avoid losing their way when navigating from offshore waters back to river mouths. Conversely, if fishermen wish to return shortly after nightfall, the helmsman observes sao hôm, which rises around seven or eight o’clock in the evening, and follows its direction to guide the vessel swiftly back to shore. Long-time fishermen also possess the ability to interpret the color of the sky’s afterglow (ráng trời). If the afterglow shifts to a dark purplish hue rather than its usual bright red, it is understood as a sign that the sea will become rough in the following days, making fishing difficult and necessitating a return to shore.
In addition, fishermen observe certain phenomena occurring on land to anticipate weather conditions at sea. Women at home, when cooking over a fire, may predict an approaching storm if they notice small embers scattering chaotically after removing the pot from the stove. Likewise, the sudden appearance of swarms of winged ants flying erratically inland causes great concern among families with relatives at sea, as reflected in the saying: "Kiến cánh vỡ tổ bay ra, bão táp mưa sa gần tới" (winged ants leaving their nests signal the imminent arrival of storms and heavy rain) (NTT, female, 75 years old, An Thủy commune, November 2022).
Overall, fishermen in the Mekong Delta possess a vast and diverse body of experiential knowledge related to storms and rainfall. It is difficult to fully enumerate these experiences, as they vary according to each individual’s accumulated skills and personal encounters with the sea.
From an environmental adaptation perspective, the hydrological and meteorological knowledge of fishermen in the Mekong Delta has been formed and accumulated through long-term, direct, and continuous interaction with the marine ecosystems of the East Sea and the southwestern sea. This constitutes a form of practical ecological knowledge, distilled from lived experience, labor, and repeated encounters with risk within a distinctive maritime space where monsoon winds, tidal regimes, storms, and island-estuary geomorphology strongly shape fishing-based livelihoods. Unlike modern scientific knowledge, which relies on technological measurement and forecasting, fishermen’s knowledge is grounded in fine-grained observation, multisensory integration, and close attunement to the natural rhythms of the marine ecosystem. First, knowledge of monsoon winds reflects fishermen’s deep adaptation to the contrasting climatic and hydrological structures of the two sea regions. The clear distinction between the northern and southern monsoon winds, together with their cyclical patterns organized according to the lunar calendar, demonstrates that fishermen not only recognize natural phenomena but also actively organize fishing schedules, select fishing methods, and determine vessel mobility in accordance with specific sea states. This illustrates a reciprocal relationship between humans and the ecological environment: while environmental conditions shape livelihood practices, human knowledge functions to reduce risk and optimize resource exploitation within the ecological limits imposed by nature. Second, knowledge of tides and water levels reveals fishermen’s profound understanding of the interconnected river-sea system characteristic of the lower Mekong Delta. The ability to distinguish between the semi-diurnal tidal regime of the East Sea and the diurnal regime of the southwestern sea, along with the precise calculation of "main tides" and "high-low water" cycles over half-monthly periods, reflects fishermen’s capacity to interpret the hydrodynamic rhythms of the coastal ecosystem. Such knowledge is essential not only for safe navigation through river mouths but also for determining the effectiveness of fishing practices such as fixed traps (đóng đáy), nò xiêm, or brush shelters (thả chà), all of which depend closely on water levels and current flows. Third, the body of knowledge related to rainfall, storms, and natural indicators such as migratory birds, surfacing fish, cloud formations, stars, atmospheric glow (ráng trời), rainbows, and inland phenomena demonstrates that fishermen have constructed an indigenous "early warning system" based on observational ecology. These indicators reflect the organic interconnections among components of the marine ecosystem, including the atmosphere and marine life, whereby changes in one element may signal broader systemic disturbances. In the absence of modern communication technologies, this knowledge has functioned as a vital survival mechanism, enabling fishermen to proactively avoid hazards and safeguard both life and property. Finally, knowledge of maritime space, islands, and navigation routes reveals a process of ecological "mapping" through collective memory and folk literature, such as sea-faring chants, proverbs, and place-name verses. These forms of knowledge not only hold practical value for orientation, identifying shelters, and accessing freshwater sources, but also reflect the ways in which fishing communities construct, preserve, and transmit ecological understanding of marine space across generations. Overall, the weather-related knowledge of fishermen in the Mekong Delta is deeply intertwined with the distinctive wind and storm patterns of the East Sea and the southwestern maritime region. This interdependence highlights the uniqueness and contextual specificity of these experiential forms of knowledge, rooted in the ecological conditions of the region.
These findings allow for a clearer interpretation, from the perspective of Julian Steward’s cultural ecology, of which forms of indigenous knowledge continue to function as a resilient cultural core within fishing-based livelihoods. According to Steward’s cultural ecology framework, the "cultural core" comprises those forms of knowledge and practices most closely tied to subsistence activities and economic organization. As such, these elements tend to be more resilient to social change, as they directly determine labor capacity, safety, and the efficiency of resource extraction within a community. In the context of coastal fishers in the Mekong Delta, who simultaneously confront heightened weather-related risks and the depletion of marine resources, indigenous knowledge that continues to operate as a relatively stable cultural core can be identified in three main domains: (i) knowledge of monsoon winds, tidal cycles, and currents, including the ability to "time" departures and returns at river mouths to ensure safety and optimize fishing trips; (ii) knowledge related to the spatial organization of livelihoods, expressed through experiential "maps" of channels, estuaries, fishing grounds, and localized micro-fishing areas; and (iii) knowledge of seasonal cycles, migratory behavior, and reproductive patterns of key target species, which informs decisions regarding fishing gear, timing of exploitation, and labor intensity. These forms of knowledge are directly linked to economic performance and risk management, and therefore continue to retain high practical value and to be reproduced through everyday fishing practices. By contrast, certain forms of indigenous knowledge have been eroded or transformed under the combined influence of modern technologies and ecological change, particularly skills related to weather forecasting based on subtle environmental cues—such as the color of the sky’s afterglow, cloud formations, bird behavior, or stars—and experiential practices of "reading the sea." As many fishing vessels increasingly rely on GPS systems, radio communication, and fish-finding technologies, these traditional skills are less frequently mobilized. However, this process does not represent a complete displacement of indigenous knowledge. Rather, it is more accurately characterized by coexistence and internal reconfiguration. While modern technologies enhance accuracy and a sense of security at sea, fishers continue to draw upon traditional knowledge in situations involving signal loss, forecast uncertainty, or the need for rapid, on-site decision-making—for example, observing stars to infer wind direction and guide navigation. Indigenous knowledge should therefore be understood as a dynamic adaptive system, in which core elements closely tied to livelihoods remain relatively stable, while more peripheral components undergo transformation in response to technological change and environmental variability.
Knowledge of Marine and Aquatic Resources
The marine area of the Mekong Delta is endowed with abundant and diverse fishery resources, including pelagic, demersal, and deep-sea species. According to Mai et al. (2015), this region is home to a wide range of representative families, such as mullets, croakers, pufferfish, ponyfish, tonguefish, and squids (pp.375). As one of Vietnam’s major fishing grounds, marine capture fisheries in the Mekong Delta have expanded and developed continuously over recent decades. Through long-term fishing activities, fishermen have gradually formed a body of knowledge enabling them to identify nearshore and offshore marine resources and to distinguish seasonal patterns in the growth and movement of fish and shrimp stocks.
For generations, fishermen have recognized that these waters support a wide variety of fish species, including pomfret, mackerel, cá gúng, rays, silver sillago, squid, and shrimp. These resources are perceived as "lộc trời" (blessings from nature), providing livelihoods and income security for fishing households. As such, this knowledge constitutes a valuable body of folk ecological knowledge. As fishing activities extend from coastal to offshore waters, fishermen are well aware of brackish-water species commonly found near estuaries and marine species inhabiting offshore areas, in addition to the rich presence of crustaceans and mollusks.
Our research findings indicate that each coastal locality in the Mekong Delta hosts distinctive assemblages of aquatic species rather than identical compositions, thereby contributing to the formation of localized marine "specialties." For example, in Vàm Láng town (Gò Công Đông district, Tiền Giang province), long-time fishermen report abundant catches of lizardfish, croaker, tongue sole, anchovy, blue clam (vòm xanh), razor clam, blue swimming crab, and shrimp. In Bình Thắng commune (Bình Đại district, Bến Tre province), common species include yellowstripe scad, hairtail, lizardfish, silver sillago, herring, and mullet. In An Thủy commune ( Ba Tri district, Bến Tre province), fishermen typically harvest pomfret, sardine, silver sillago, scad, and rays. In Trà Vinh province, fishermen at the Mỹ Long and Định An estuaries primarily exploit , mackerel, yellowstripe scad, tongue sole, and hairtail. Trần Đề town (Sóc Trăng province) is characterized by frequent offshore fishing, yielding catfish, mullet, blue trevally, cutlassfish, shrimp, and dried squid. At the Gành Hào estuary (Đông Hải district, Bạc Liêu province), fishermen mainly catch croaker, trevally, sailfish, marine snakehead, silver sillago, hairtail, and tongue sole. In Sông Đốc estuary (Trần Văn Thời district, Cà Mau province), fishermen harvest tuna, barracuda, silver sillago, cobia, grouper, rays, herring, mackerel. Notably, this area is also a major breeding ground for squid (reef squid, longfin squid, cuttlefish) as well as mantis shrimp and crab. Offshore waters of Kiên Giang province host a wide range of species, including sharks, grouper, tuna, cobia, amberjack, snapper, blue-spine fish, squid, lobster, crab, and swimming crab.
Recognizing the life cycles of marine species constitutes a crucial component of fishermen’s knowledge in the Mekong Delta. This experiential understanding enables fishermen to plan fishing activities at different times of the year. According to Phan Thị Yến Tuyết (2014), fishermen in the region clearly identify seasonal fish availability by month: January is associated with silver sillago, hairtail, cá chét (Ilisha spp., shad), croaker, and anchovy; February, March, and April yield scad and mackerel; May, June, and July are dominated by a single major species; September and October see catches of cá rựa, cá đổng, sardine, cá ba thú, and cá ba lài; while November and December, extending toward the Lunar New Year, mark the peak season for silver sillago (pp. 481–482). Our fieldwork in An Thủy commune (Ba Tri district, Bến Tre province) reveals locally specific variations in these seasonal patterns. Elder fishermen report that from January to March, silver sillago, sardine, and cá lẹp dominate; March and April bring cá rựa, pelagic fish, mackerel, and cá ét; May marks the season for cá giang, cá theo, and cá rựa; by July, cá lò tho, cá trau tráu, and cá mòi gà become abundant. Shrimp resources are also well understood: from February to May, tôm sắc mọi and reef-bottom shrimp are common, while September through November are associated with tôm sắc gộc and tôm bạc nghệ. At the Sông Đốc estuary, experienced fishermen describe detailed offshore seasonal cycles: January to March sees anchovy, herring, scad, tuna, and cá mắt lộ migrating in large schools; April to June yield pomfret and mackerel; July and August are marked by cá ba thú, scad, anchovy, and herring; November and December bring sardine, cá lẹp, and cá ba thú. Longfin squid peak from February to May, while cuttlefish are most abundant during the northeast monsoon (October to December). Mantis shrimp appear in large numbers in March and April, whereas whiteleg shrimp proliferate during the southern monsoon season (February–March). Several elderly fishermen further recall that approximately 30 years ago, from the 10th to the 25th day of the third lunar month, the Sông Đốc estuary entered the peak season of cá đường. These fish appeared in massive schools swimming close to shore, allowing for abundant harvests. Prior to 1975, fishing vessels from Singapore reportedly traveled to this area to purchase cá đường swim bladders, which were used as food ingredients and surgical materials in medical applications.
From an environmental adaptation perspective, knowledge of marine resources among Mekong Delta fishermen is the product of long-term, continuous, and direct interaction between humans and the marine ecosystems of the East Sea and the southwestern sea. Within a highly productive yet seasonally dynamic marine environment, fishermen have accumulated a body of practical ecological knowledge enabling species identification, habitat zoning, and understanding of growth cycles and migratory patterns of fish, shrimp, and squid. This knowledge reflects both livelihood adaptation to natural conditions and the capacity to "read" the marine environment through intergenerational labor experience. The diversity of pelagic, demersal, and deep-sea species has provided the ecological foundation for fishermen’s folk classification systems. Beyond naming species, fishermen distinguish habitats (estuaries, coastal waters, offshore zones), seasonal availability, and economic value. The memorization and oral transmission of species knowledge through folk verses and chants indicate that ecological knowledge has been culturally embedded, forming part of collective memory and maritime occupational identity, thereby facilitating intergenerational learning and practical application. Furthermore, knowledge of the ecological specificity of sub-regions such as Tiền Giang, Bến Tre, Trà Vinh, Sóc Trăng, Bạc Liêu, Cà Mau, and Kiên Giang reflects spatial differentiation of marine resources shaped by hydrological conditions, seabed geomorphology, and current regimes. Fishermen do not perceive the sea as a homogeneous space but rather recognize distinct "micro fishing grounds" characterized by specific species assemblages. This spatial understanding informs the selection of fishing gear, fishing methods, and timing of voyages, optimizing extraction efficiency within the ecological limits of each area. Knowledge of growth cycles and seasonal availability further demonstrates the close linkage between marine ecosystems and fishermen’s livelihood calendars. Seasonal classification by lunar months reflects fishermen’s integrated observation of monsoon winds, water temperature, currents, and migratory behavior of marine organisms. This knowledge serves not only economic purposes but also functions as an informal regulatory mechanism, discouraging off-season overexploitation and contributing to the long-term renewability of marine resources. Overall, knowledge of marine and aquatic resources among Mekong Delta fishermen is the product of co-construction between human communities and the marine ecosystems of the East Sea and the southwestern maritime region. This knowledge system embodies ecological, economic, and cultural values and plays a critical role in sustaining coastal livelihoods. In the context of climate change, resource depletion, and increasing exploitation pressures, recognizing, preserving, and integrating indigenous knowledge into marine resource management represents a necessary approach to enhancing adaptive capacity and promoting sustainable development in the Mekong Delta’s coastal seas.
Conclusion
Addressing the two research questions posed in this study, the findings demonstrate that indigenous ecological knowledge continues to function as a critical adaptive resource for coastal fishing communities in the Mekong Delta. Through the everyday mobilization of weather-related, hydrological, and marine resource knowledge, fishers in An Thủy and Sông Đốc actively anticipate environmental risks, organize fishing activities, and sustain livelihoods under conditions of climate variability and ongoing resource depletion. At the same time, the analysis reveals that specific domains of indigenous knowledge particularly those directly linked to subsistence practices and fishing-based economic organization constitute a resilient cultural core in the sense articulated by Julian Steward, even as other forms of knowledge face gradual erosion under technological change and ecological pressure.
In sum, the indigenous knowledge of coastal fishing communities in the Mekong Delta forms a relatively comprehensive system encompassing knowledge related to weather, hydrology, and marine living resources, accumulated, transmitted, and practiced across generations. This system has enabled fishers to conduct fishing activities with confidence and, over time, to expand their livelihoods from nearshore waters to offshore fishing grounds. Indigenous knowledge in this region therefore reflects a long-term process of human adaptation to the marine environment of the Mekong Delta, shaped through sustained residence and continuous interaction with the sea. As such, these knowledge forms represent lived experience and everyday practices of adaptation, coping, and risk management embedded within the local marine ecosystem.
From a theoretical perspective, drawing on Julian Steward’s cultural ecology, the indigenous knowledge of hydrology, weather, and marine resources among Mekong Delta fishers may be understood as a cultural core reflecting direct adaptation to a distinctive and dynamic marine environment. This study demonstrates that such knowledge has not only emerged from intergenerational practical experience but has also been continuously adjusted in response to environmental change. Importantly, the findings show that the adoption of modern fishing technologies does not uniformly displace indigenous knowledge; rather, it selectively reshapes its internal structure, allowing core adaptive competencies related to safety, navigation, and seasonal decision-making to persist alongside new technological practices. Indigenous knowledge should therefore be understood not as a static tradition, but as a dynamic and context-specific adaptive system.
Despite its continuing adaptive value, much of this indigenous knowledge remains orally transmitted and is primarily preserved by elderly fishers, placing it at considerable risk of erosion over time. This knowledge system holds not only cultural and social significance but also profound ecological and sustainability value, particularly in the context of climate change, increasing weather extremes, and the ongoing depletion of marine resources. Identifying, preserving, and integrating indigenous knowledge into marine resource management thus represents a necessary strategy for strengthening the adaptive capacity of coastal fishing communities.
At present, fishing activities in the Mekong Delta increasingly rely on modern technologies installed on vessels, such as GPS navigation systems, fish finders, and radio communication devices. While these technologies enhance efficiency and a sense of security at sea, they have also contributed to a declining reliance on certain traditional skills, especially those related to interpreting subtle weather changes and fish behavior. Nevertheless, continued research and systematic documentation of indigenous knowledge in coastal localities of the Mekong Delta remain urgently needed to safeguard this valuable knowledge heritage and to retain practical experiences that continue to support safe offshore fishing under conditions of intensifying climate change.
Fieldwork in An Thủy commune and Sông Đốc town further indicates that although many fishers today feel more secure due to modern equipment, some still regard traditional weather-related knowledge as useful, particularly given the persistent uncertainties and limitations of contemporary weather forecasting. In contrast, elderly fishers express concern that many younger fishers lack familiarity with indigenous knowledge systems and rely almost entirely on media-based forecasts. This gradual loss of knowledge is widely perceived as regrettable and underscores the need for appropriate preservation strategies. As Nguyễn Chí Bền (2019) argues, encouraging communities to continue using indigenous knowledge and experiential practices in marine exploitation and coexistence with the sea is essential. Given that these knowledge forms are largely oral traditions, there is an urgent need for projects aimed at collecting, documenting, and textualizing folk knowledge related to the sea. Such efforts would not only contribute to cultural heritage preservation but also enable contemporary fishers to reference and apply knowledge that remains relevant and effective, thereby sustaining and revitalizing positive elements of ancestral maritime experience in present-day fishing practices.
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