Effects of Anthropogenic Activities on Sardinella maderensis (Lowe, 1838) Fisheries in Coastal Communities of Ibeju-Lekki, Lagos, Nigeria
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1. Introduction
Fisheries support about 600 million people’s livelihoods and supply 214 million tons of fish and 17% of animal protein consumption among the world’s population [1,2]. Globally, fish, among other aquatic foods, are high-demand products, reaching a production value of USD 424 billion in 2020 and substantially contributing to many countries’ gross domestic products (GDPs), alleviating poverty and fostering nutritional security [2]. In Nigeria, fish is a vital source of protein, and fisheries constitute a significant sector of the economy, contributing approximately 5.40% of the country’s GDP [3]. A country report by the FAO [4] states that small-scale fisheries dominate fish production in Nigeria by contributing over 80% of Nigeria’s total domestic fish production. Small-scale fisheries are prominent along the Nigerian coast, especially along the Ibeju-Lekki coastline, which extends for about 75 km of the total 180 km of the Lagos state coastline, contributing the highest percentage of fish caught with respect to other coastal sections [5]. The fisheries are multi-species fisheries with a dominance of Sardinella spp. and Caranx spp. [6,7,8]. Despite high catches of these species that have attracted local artisanal fishers and foreign nationals, there is limited knowledge of the effect of anthropogenic factors on the abundance indices of the Sardinella spp. on the Lagos coastline, which have some of the highest economic values to the fisherfolk [7].
Sardinella maderensis (Lowe, 1838) is commonly known as Madeiran sardinella or flat Sardinella and is locally called Sawa. It is a schooling pelagic fish from the Clupeidae family [9]. It has an elongated body with a variable depth, black or blue/green colouring, and silvery flanks. Its size is usually 20–25 cm, and it inhabits the near-surface of coastal waters, shoaling at the surface or the bottom, down to 50 m. It feeds on various small planktonic invertebrates, fish larvae, and phytoplankton. S. maderensis is presently found in 43 countries worldwide, with Africa dominating the global fish catch. Using a ten-year average (2008–2017), Nigeria is the third highest contributor of S. maderensis, being responsible for 9% of the species’ global catch [10]. S. maderensis dominates small-scale marine fisheries and is the main species captured in Nigeria’s coastal waters, providing livelihood sources, nutrition, and income for several poor coastal communities in Nigeria [4]. S. maderensis is one of Nigeria’s most abundant and economically valuable coastal pelagic species [11,12]. It accounts for 69% of the fish caught by artisanal fishers in the Ibeju-Lekki locality [7].
In the last few decades, anthropogenic activities have increased along the Nigerian coastline due to rapid population growth linked to industrialisation [13,14]. This growth has resulted in significant human pressures on marine ecosystems and biological stocks [15]. Massive industrial activities and urban developments have threatened the pelagic fish populations due to the degradation of coastal habitats in which S. maderensis is endemic [12,16]. Moreover, industrial developments associated with the Lekki Free Trade Zone, including dredging and land reclamation for the construction of the seaport and the petrochemical refinery, have destroyed mangroves and coastal habitats crucial to S. maderensis [15]. Polluting effluents such as petroleum hydrocarbons and heavy metals from industries threaten water quality, causing a decline in ecosystem services and environmental sustainability [17,18,19]. In addition, inefficient fishing standards and illegal and unregulated fishing have negatively impacted the fisheries’ sustainability, leading to significant changes in species composition and decreased catches [20,21]. Altogether, escalating anthropogenic pressures threaten the sustainability of small-scale fisheries and the livelihoods of Ibeju-Lekki communities.
A few studies have investigated the effects of anthropogenic activities on fisheries, emphasising the impacts on the broader coastal fisheries in Nigeria [22,23]. However, there is limited knowledge on how increasing anthropogenic activities affect S. maderensis fisheries and the livelihoods of fisherfolk in the coastal communities of Ibeju-Lekki. Filling the knowledge gap respecting the effects of anthropogenic activities on S. maderensis fisheries in Ibeju-lekki is imperative for building fishers’ resilience and achieving the Sustainable Development Goals (SDGs) 1, 2, and 14. Moreover, findings from the study will provide empirical evidence on how anthropogenic activities affect S. maderensis fisheries and fishers’ livelihoods in Nigeria. The outcome will inform policy interventions to mitigate pollution, habitat degradation, and over-exploitation, promoting resilience in small-scale fisheries that will sustain livelihoods and conserve biodiversity in Nigeria.
In its objectives, the study sought to confirm the identity of the Sardinella species exploited in Ibeju-Lekki fisheries using genetic and morphological techniques; analyse the land use and land cover changes over time using geospatial analysis; and assess water pollution levels and habitat degradation through water quality analysis. Anthropogenic factors were correlated with S. maderensis abundance to examine what relationships exist. The fisherfolks’ perceptions of anthropogenic impact and vulnerability were elucidated, and strategies for mitigating anthropogenic threats and promoting resilient small-scale fisheries were recommended for adoption.
2. Literature Review
Globally, small-scale fisheries employ millions of fishers and are significant sources of nutrition, food security, and livelihood, catering for many people [24]. However, increasing anthropogenic pressures threaten the sustainability of many small-scale fisheries [25,26]. Major anthropogenic threats include pollution and habitat degradation from coastal developments and overfishing [27,28,29]. These human activities pose severe sustainability threats to small pelagic species, which support food security in West Africa [30]. These stresses damage breeding grounds, reduce productivity, and threaten important species like S. maderensis [31,32].
S. maderensis is a dominant species in Nigerian small-scale fisheries [4]; however, the species is rated by the International Union for Conservation of Nature (IUCN) as “vulnerable” [12]. According to Akintola and Fakoya [14], the availability of the Clupeids family, to which Sardinella spp. belong, has diminished over the last decade due to habitat destruction and overfishing. Furthermore, the existing literature on the spatiotemporal dynamics, demographic parameters, and abundance indices of S. maderensis have focused on other West African coasts, excluding Nigeria. These include areas of the Ivory Coast [33], Cameroon [34], Benin [35], Liberia [36], and Ghana [37]. Being a vulnerable species, understanding anthropogenic impacts on S. maderensis is crucial to its sustainable management and conservation efforts; hence, correct species identification and insight into its genetic diversity are essential for its adaptability and resilience to human-induced and environmental changes [38,39,40]. Moreover, measuring the anthropogenic effects on S. maderensis species has been constrained by limited stock assessments and species identification, which provide pivotal knowledge for fisheries management [41,42,43]. Despite calls by the Food and Agricultural Organization [44] for species-specific research on the S. maderensis species in Nigeria, this has remained elusive; therefore, this study undertakes species identification as a precursor to investigating anthropogenic threats to S. maderensis fisheries.
Lagos’s extensive coastal area has undergone rapid transformation due to urbanisation, industrialisation, and population growth, creating complex environmental problems due to unpredictability and scale diversity [45]. The increasing demand for fish for human consumption has steadily increased the fishing efforts of small-scale fisheries in recent years [46]. While these escalating pressures threaten the sustainability of small-scale fisheries, only a few studies have elucidated localised risks and impacts, including the effects of anthropogenic pressures on the S. maderensis fisheries in Nigeria [8,14,47,48]. Hence, explicating localised threats will inform policies for the sustainability of the S. maderensis fisheries and fishers’ livelihoods in Lagos’s coastal waters.
5. Discussion
This study provides empirical evidence on how growing anthropogenic pressures driven by industrialisation affect the S. maderensis fisheries, which coastal communities depend on for their nutrition and livelihoods. The massive land reclamation for constructing the Lekki Deep Sea Port and the petrochemical refinery has extensively damaged the coastal ecosystems in Ibeju-Lekki over time. Effluents from industrial and port activities also significantly pollute the coastal waters, increasing the anthropogenic pressures that threaten small-scale fisheries’ sustainability. While these massive developments seem to have economic advantages, they have inadvertently contributed to the decline of the S. maderensis fisheries, which are depended upon for nutrition and livelihoods in Ibeju-Lekki. However, several studies have emphasised balancing economic development, environmental conservation, and fisheries sustainability [92,93,94,95,96,97].
The land-use change analysis of Ibeju-Lekki reveals extensive change to urban/industrial development in the past 36 years, leading to the loss of mangrove and coastal forested areas. The findings of this study align with previous research conducted in other tropical regions, which emphasises the negative impacts of unsustainable coastal development on the resilience of fishing communities [98,99,100]. Mangroves, seagrass beds, and other coastal habitats are crucial as nursery grounds and provide ecological support for S. maderensis fisheries [101,102]. Previous studies show a correlation between declines in fish populations and habitat loss and degradation [103,104,105,106]. Consequently, the loss of habitats from anthropogenic activities like dredging, sand filling, construction, and industrial effluents destroys the ecological resources that sustain the S. maderensis fisheries in Ibeju-Lekki. Mitigating these adverse impacts requires spatial planning with integrated ecological knowledge and the enforcement of strict environmental management policies to protect fisheries and marine life [107].
Furthermore, the need for stringent environmental policies cannot be overemphasised, as industrial pollution creates a toxic ecosystem for fish survival. The physical and chemical parameter analysis results in Table 6 showed that water temperature, pH, salinity, dissolved oxygen, nitrate (NO3), and phosphate (PO4) levels were still within the ranges tolerable by S. maderensis [75,108]. However, the total dissolved solids (TDSs) values ranged between 11,500 mg/L and 30,000 mg/L and were higher than the acceptable limit of 2000 mg/L set by the Federal Environmental Protection Agency. These high TDSs values may affect gill and kidney functions and impact the survival and size of the fish. Mahboob et al. [109] recorded higher values of TDSs in their study of the Arabian Gulf, Saudi Arabia, which was also characterised by prevalent anthropogenic activities similar to those found in Ibeju-Lekki, such as sand dredging, landfilling, and oil spills. The biological oxygen demand (BOD) values occasionally fell within an acceptable range but sometimes exceeded the lethal limit, with values as high as 11 mg/L. Hynes [74] states that BOD values higher than 8 mg/L point to severe pollution. The chlorophyll-a levels observed in Table 6 are inadequate, indicating insufficient phytoplankton abundance, potentially adversely affecting the S. maderensis populations due to their planktivorous feeding habits. Abdellaoui et al. [110] observed in their studies that changes in chlorophyll-a have a significant impact on sardine abundance, linking minimal chlorophyll-a levels to the gradual decline in yields of sardines in Al Hoceima, South Alboran Sea. Marine phytoplankton are essential not only as food to some fish species but also because they form the foundation of the marine food web [111,112].
The heavy metal analysis results indicate the effects of industrial pollution from the petrochemical refinery and deep sea port activities. These heavy metal analysis results can be used as baseline values for water quality in Ibeju-Lekki coastal waters because many industries have just started functioning within the last few years. Table 7 reveals that the lead, cadmium, iron, manganese and nickel levels, were within the national limits set by the FEPA in Nigeria but above the international standard limits. Also, the value for chromium in mg/L was above both the local and international standard limits. Previous studies attributed heavy metal pollution to anthropogenic activities in coastal waters [113,114]. For example, lead pollution could be due to oil spills, motorboats, and untreated wastes [114]; other sources include higher concentrations of metals from corrosion in marine construction, landfilling, and construction residuals [109]. The TPH values in the waters of the Ibeju-Lekki communities exceeded the limits of the FEPA standards, which could be attributed to oil spillage in the water [115]. These levels could lead to severe biological and economic impacts on the marine environment, which calls for an urgent regulatory intervention.
The decline in S. maderensis CPUE shown in the trend analysis (Figure 6) indicates a declining fish stock and a relatively low fish abundance over time. While a declining trend in CPUE is a common concern in fisheries management, it is often attributed to overfishing or ecosystem degradation [39,116]. However, the R2 = 0.3886 shows that about 61% of the variation in the CPUE is not explained by the time variable alone, suggesting other possible factors like environmental changes, economic or social policy changes, and unsustainable fishing practices. The research also indicates that without a significant shift in fisheries management and conservation practices, the trend may likely continue, aggravating the challenges faced by the marine ecosystem and fishing communities [117].
The fishers’ perceptions discussed in Section 4.5 reveal that four anthropogenic factors significantly predict S. maderensis abundance. The regression analysis in Table 8 shows that these four independent variables—fishing effort, needed amenities, land use effect, and access to markets—were statistically significant, accounting for 40% of the variability in CPUE, representing fish abundance. This indicates a relatively strong relationship between these anthropogenic factors and rates of catching fish. This finding is consistent with previous findings on the influence of anthropogenic factors on fish stocks, which has been well documented in fisheries science [118,119,120,121,122,123,124]. Also, aligning findings from fishers’ perceptions with the literature indicated that LEK is crucial in understanding non-biological stressors predicting fish abundance [67,68,71,125].
Fishers in Ibeju-Lekki considered fishing efforts to have a negative relationship with fish abundance. Table 8 shows that CPUE decreases by 7.45 units for every unit increase in the fishing effort variable (V_FISH_EFFORT). This result corroborates the literature on the effect of overfishing on fish abundance [39,117,126]. This result requires that fishing efforts be managed to avoid overexploitation and ensure the sustainability of the S. maderensis fisheries. Previous studies suggested that controlled fishing practices and fisheries management systems, grounded on rights-based principles that co-opt fishers in the management process, could help mitigate overfishing and empower fishing communities effectively [39,127].
Furthermore, this research corroborates previous studies asserting that land use and habitat alterations can significantly impact marine ecosystems and fish abundance [118,119,128]. The results in Table 8 show that the land-use effect variable (V_LANDUSE) is a significant predictor of fish abundance, with a negative coefficient of −0.85 (p = 0.002), indicating that the ongoing massive coastal developments like the petrochemical refinery, the deep sea port, and other significant urban developments have a negative impact on the S. maderensis fisheries. The results underscore the need for sustainable marine spatial planning (MSP).
In addition, the government and stakeholders should augment MSP by providing needed amenities and market access. On the one hand, needed amenities (V_AMENITY) negatively predicts CPUE with a regression coefficient (B) value of −3.23 (p p 129,130] on the role of socioeconomic drivers in sustaining small-scale fisheries.
The findings generally emphasise the necessity of adopting a comprehensive and inclusive strategy for coastal development that safeguards the fundamental natural resources that sustain the local population’s livelihoods [131]. Presently, existing development plans and policies for Ibeju-Lekki emphasise top-down development strategies prioritising industrial enterprises, aiming to achieve economic benefits. However, these policies overlook the socio-ecological impacts on marginalised small-scale fisheries [132]. Nevertheless, neglecting these consequences undermines long-term sustainability. Hence, an ecosystems-based approach in fisheries management and an integrated marine spatial planning strategy for land and water use are needed to conserve vital fish habitats [133,134]. Implementing rigorous water quality monitoring and strict enforcement of effluent standards is crucial for mitigating industrial pollution, and controlling detrimental activities such as unregulated sand dredging, which harms resilience, is also necessary. Additionally, the implementation of fisheries management systems based on rights-based principles has the potential to mitigate overfishing and empower fishing communities effectively [135]. In general, mitigating anthropogenic threats necessitates the implementation of multi-level governance approaches that effectively balance economic development, ecological sustainability, and social equity [136].
This investigation provides a framework for research approaches to assess anthropogenic threats in small-scale fisheries in developing countries. In summary, this research highlights the importance of addressing human-induced challenges such as pollution and habitat loss to ensure the sustainability of small-scale fisheries, which play a vital role in providing employment, food security, and nutrition in rapidly developing coastal regions.
6. Conclusions
This research investigated the effects of anthropogenic activities on small-scale fisheries, which play a crucial role in supporting the livelihoods of economically disadvantaged populations in the coastal regions of Nigeria. The study highlights threats posed by pollution, extensive habitat loss, and degradation due to rapid urbanisation and industrialisation over the past few decades in Ibeju-Lekki, leading to the depletion of mangrove ecosystems, which are crucial breeding grounds for fish like S. maderensis. The findings underscore the urgent need for inclusive fisheries management and sustainable coastal development strategies to safeguard these vital ecosystems and dependent fishing communities to foster the resilience and conservation of the S. maderensis fish species. High levels of hydrocarbon pollution and heavy metals from industrial effluents create a toxic marine environment detrimental to the productivity and survival of small pelagic species like S. maderensis. The significant decline in fish abundance over the past two decades, coupled with the fishers’ perceptions, indicates the adverse impact of habitat loss through land use change, overfishing, lack of needed amenities, and the need for economic opportunities for fishing communities that support local livelihoods and food security.
This study contributes to the growing body of evidence calling for a sustainable and inclusive approach to coastal and marine resource management, especially in the Global South and the need for MSP, stricter pollution control, habitat restoration, and biodiversity conservation. The study combines qualitative and quantitative approaches with ecosystems-based management strategies to understand the multifaceted impacts of anthropogenic activities on small-scale fisheries. Also, the study addresses the existing data gap respecting S. maderensis fisheries in the coastal regions of Nigeria, which have been previously identified by the FAO [44], thereby giving critical insights into the pros and cons of sustainable fisheries management in similar contexts. Applying genetic and morphological techniques to identify the Sardinella spp. species exploited in the region enhanced the accuracy of our research findings. It also provided a better scientific understanding of the current status of the Sardinella spp. stock in Ibeju-Lekki coastal waters. In addition, the research methods and findings provide a foundation for future studies in the fisheries sustainability domain, where incorporating scientific evidence and the LEK of fishing communities into ecosystems-based management strategies can contribute to small-scale fisheries in the coastal region, thereby attaining SDG 14.
Future investigations should broaden the spatial and temporal scope by employing ecosystem modes to unearth the complexities regarding small-scale fisheries dynamics and anthropogenic impacts for more insights into strategies for mitigation and adaptation. We suggest an inclusive multi-stakeholder approach to fisheries management involving the state, fishing communities, non-governmental organisations, and the private sector. Policies should prioritise the protection of habitat and marine resources, pollution control, regulation of fishing efforts, amenities provision, market development, and economic incentives for fishing communities. This research has shed light on anthropogenic impacts affecting small-scale S. maderensis fisheries in the coastal area of Nigeria. Implementing the recommendations will require concerted efforts that align with SDG 14. Incorporating empirical evidence and local ecological knowledge into the ecosystems-based management of fisheries will birth resilient small-scale S. maderensis fisheries supporting sustainable livelihoods, nutritional well-being, and biodiversity conservation in rapidly developing coastal areas.
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