Physicochemical interactions with fish species composition and diversity in artisanal fisheries of the cross-river estuary, cross river state, Nigeria

Artisanal fisheries are often challenged by environmental changes and increasing fishing pressure, threatening biodiversity, abundance and local livelihoods. This study examined the seasonal dynamics of fish species composition, abundance, and diversity from April 2024 to March 2025 through monthly sampling at four estuarine sites, captured using traditional fishing gears. Identification and biodiversity assessments encompassed 20 fish species spanning diverse families, analyzed with Margalef’s richness, Shannon-Wiener diversity, evenness, and Berger-Parker dominance indices. Water quality variables including temperature (27.3–29.8°C), pH (6.8–7.3), dissolved oxygen (5.4–7.2 mg/L), and turbidity (11.4–19.2 NTU) were concurrently recorded. Total fish abundance ranged between 261 and 362 individuals monthly, reflecting a diverse assemblage with dominant species such as Tilapia zillii, Clarias gariepinus, and Ethmalosa fimbriata. Margalef’s richness index peaked at 3.75 and Shannon-Wiener diversity at 2.85 in April, indicating maximum biodiversity in the late dry season. Fish density varied spatially, with peak values of 4.0±0.6 individuals/m², underscoring habitat heterogeneity. There were significant (p