International Journal of Aquaculture, 2025, Vol.15, No.6, 275-286 http://www.aquapublisher.com/index.php/ija 278 The area is characterized by brackish lagoons, estuaries, tidal creeks, and extensive mangrove swamps, which provide nursery and feeding grounds for diverse fish species. Its hydrology is influenced by tidal oscillations, seasonal rainfall, and freshwater inflows, all of which regulate salinity gradients, nutrient cycling, and primary productivity in the aquatic system (Akinyemi et al., 2021). The climate is typically tropical, with two main seasons: a wet season (April–October) with annual rainfall ranging between 1 800~2 500 mm, and a dry season (November–March). Peak rainfall occurs between June and September, accompanied by flooding and high turbidity, while the dry season is associated with reduced water levels and salinity fluctuations (Oyediran et al., 2021). These environmental dynamics strongly influence fish breeding, recruitment, and artisanal fishing activities. Fishing is the primary livelihood activity in these communities. Artisanal fishers use gillnets, cast nets, traps, and hook-and-line methods to harvest ecologically and economically important species such as Ethmalosa fimbriata (bonga shad) and Chrysichthys macropogon (catfish). These species are significant sources of food security, nutrition, and household income in Ilaje (Adeyemi et al., 2020). However, the coastal environment faces increasing anthropogenic pressures. Oil exploration, sand mining, urban expansion, and coastal erosion have been identified as major drivers of ecological degradation (Ibigbami et al., 2023). Studies in the region have reported heavy metal contamination, declining fish stocks, and loss of aquatic biodiversity, underscoring the ecological vulnerability of Ilaje waters (Nwankwo et al., 2019; Olawusi-Peters and Ajibare, 2022). Given its strategic location along the Atlantic and its dependence on fisheries, Ilaje represents a critical hub for Nigeria’s blue economy. The selected study communities are therefore important case sites for understanding how pollution and ecological stressors influence the length–weight relationship and condition factor of fish species, with implications for fisheries management and sustainability. 2.2 Sample collection Fish samples were collected monthly from April to July across the four study sites: Ayetoro, Bijimi, Idiogba, and Asumogha. A lightweight monofilament gillnet measuring approximately 80 m in length, with mesh sizes ranging from 0.6 cm to 4.0 cm, was employed to capture a broad range of fish size classes (Ndome et al., 2020). Nets were set in the evening between 18:00 and 19:00 h and retrieved the following morning between 06:00 and 07:00 h, coinciding with peak activity periods of many pelagic and demersal species in tropical coastal ecosystems (Eyo et al., 2019). Immediately after capture, fish were removed from nets, sorted by species, and preserved on ice in insulated containers to maintain freshness and minimize tissue degradation prior to laboratory examination (Adewumi et al., 2021). Species identification was conducted using the field guide of Nigerian freshwater and marine fishes (Olaosebikan and Raji, 2013), and further validated with updated FishBase taxonomic keys (Froese and Pauly, 2023). Ethical procedures were adhered to during handling and processing to minimize stress and injury, in accordance with the FAO Code of Conduct for Responsible Fisheries (FAO, 2020). A total of 320 specimens were analyzed: 160 Ethmalosa fimbriata (bonga shad) and 160 Chrysichthys macropogon (catfish). This dataset provided a robust basis for estimating the length–weight relationship (LWR) and condition factor (K) across the sampled locations. 2.3 Length-weight relationship and condition factor The relationship between length and weight was established through linear regression, following the methodology outlined by Ajibare and Ayeku (2024), where length and weight were expressed as: W = aLᵇ
RkJQdWJsaXNoZXIy MjQ4ODYzNA==