International Journal of Aquaculture, 2025, Vol.15, No.6, 275-286 http://www.aquapublisher.com/index.php/ija 276 In Nigeria and across West Africa, artisanal fisheries play a central role in coastal livelihoods. Species such as Ethmalosa fimbriata (bonga shad), a dominant small pelagic fish, and Chrysichthys macropogon (catfish), a demersal species of commercial value, are ecologically and economically significant (Adewumi et al., 2021; Akintade et al., 2023). Both species contribute substantially to food security, trade, and cultural practices in coastal communities. However, their populations are increasingly threatened by environmental stressors, including oil exploration, coastal industrialization, and unsustainable fishing practices in the Niger Delta (Olusola et al., 2018; Ajibare and Ayeku, 2024). The Ilaje Local Government Area of Ondo State, located within the Niger Delta, is a critical fishing hub where these species are heavily exploited. Yet, despite their importance, limited studies have assessed the growth and condition of these species under the combined influence of artisanal fishing pressure and environmental variability in this region. The length–weight relationship (LWR) has long been recognized as one of the most widely applied tools in fisheries biology. It provides valuable insights into growth dynamics, population health, and ecological adaptations of fish species. Typically expressed as a power function of length and weight, LWR helps in estimating growth patterns, biomass, and energy allocation within populations (Froese, 2006; Ibrahim et al., 2022). Deviations from the expected isometric growth exponent (b = 3) indicate whether a species is undergoing positive or negative allometric growth, which often reflects environmental conditions, food availability, and reproductive status (Akinyemi et al., 2021; Eni et al., 2022). Closely related to LWR, the condition factor (K) is used as a simple but powerful indicator of fish health, reflecting the “plumpness” or well-being of individuals relative to their size. High K values typically suggest good feeding conditions, reproductive readiness, or suitable environmental quality, whereas low values may indicate stress, scarcity of food, or habitat degradation (Blackwell et al., 2020; Akintade et al., 2023). Together, these two indices serve as important bioindicators, allowing fisheries managers to assess habitat suitability and ecological stressors. Several studies in West Africa have applied LWR and K to understand the responses of fish populations to environmental variability. For instance, Adewumi et al. (2021) examined commercially important fish species in Nigerian coastal waters and reported that variations in K were strongly linked to seasonal changes and fishing pressure. Similarly, Nwani et al. (2020) observed that length–weight patterns of tropical river fishes were strongly influenced by anthropogenic stressors such as pollution and habitat modification. More recent studies have highlighted the potential of these parameters for long-term monitoring, noting that LWR and K not only provide information on stock dynamics but also serve as proxies for ecosystem health in data-poor fisheries (Olanrewaju et al., 2023; Ajibare and Ayeku, 2024). Specifically, Ethmalosa fimbriata (bonga shad) and Chrysichthys macropogon (catfish) have received increasing attention because of their ecological and commercial significance in coastal West Africa. Both species play a central role in artisanal fisheries, yet they are also vulnerable to overexploitation and environmental stress. Recent studies indicate that their LWR and K values vary significantly across habitats, reflecting the influence of coastal degradation, food availability, and fishing intensity (Udo et al., 2019; Akintade et al., 2023). Thus, understanding their growth and condition is vital for guiding sustainable fisheries management. Overall, LWR and condition factor remain indispensable tools for evaluating fish stock status. With growing environmental pressures in the Niger Delta and other coastal ecosystems, the continuous application of these indices is critical for detecting early signs of ecological imbalance, supporting conservation initiatives, and ensuring sustainable fisheries exploitation. 1.1 Studies on fish species in Nigerian waters: length–weight relationship and condition factor Ethmalosa fimbriata is one of the most abundant small pelagic fishes in West African coastal waters and plays a central role in artisanal fisheries. It provides affordable protein and serves as a major income source for coastal households (Eni et al., 2022). Several studies have reported variations in its LWR and condition factor across
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