Length-weight Relationships and Growth Patterns of Fish Assemblages in the Ikot Okubara River, Nigeria

Abstract

Aims: To derive length-weight relationship (LWR) parameters and characterize growth patterns for the fish assemblage of the Ikot Okubara River, establishing the first published baseline reference values for this previously undocumented West African tributary. Study Design: Descriptive cross-sectional field survey with laboratory morphometric analysis. Place and Duration of Study: Ikot Okubara River (approximately 5°02′01.84″N, 7°56′01.04″E), Ediene District, Abak Local Government Area, Akwa Ibom State, Nigeria, sampled monthly from May to November 2024. Methodology: A total of 269 individual fish belonging to 19 species were obtained using encircling nets, cast nets and non-return valve traps operated by local fishers. Specimens were identified using regional keys, measured for total length (TL, nearest 0.1 cm) and total weight (TW, nearest 0.1 g). Parameters a and b of the relationship TW = a·TLᵇ were estimated by ordinary least-squares (OLS) regression on log10-transformed data. Growth type was classified relative to the isometric reference value b = 3. Species with N < 5 were reported descriptively only and excluded from growth-pattern interpretation. Results: Total length ranged from 8.0 cm to 32.0 cm; total weight ranged from 4.3 g to 607.8 g. Growth coefficients (b) for species with N ≥ 5 spanned 0.3551 (Papyrocranus afer) to 2.6403 (Oreochromis niloticus). The numerically dominant species, Oreochromis niloticus (N = 122), exhibited negative allometric growth (b = 2.6403, r = 0.8803). High correlation coefficients (r > 0.86) were obtained for most well-sampled species. Conclusion: The study supplies the first LWR reference values for the Ikot Okubara River fish community. These parameters provide a quantitative baseline against which future changes in growth pattern or condition can be evaluated.