Biometric relationships and condition factor of Nile tilapia (Oreochromis niloticus) grown in concrete ponds with groundwater

Abstract

This study investigates biometric relationships in Oreochromis niloticus (gray tilapia) reared in controlled pond environments at the Centro de Investigación Piscícola (CINPIS), Universidad Nacional Agraria La Molina (Perú), over a 3-year period (2021–2023). Focusing on total length (\({L}_{t}\)), standard length (\({L}_{s}\)), height (\(H\)), and width (\(A\)), we developed models to estimate weight (\(W\)) based on these parameters, achieving strong model performances with R² values between 0.899 and 0.994. The model using \({L}_{t}\) as a predictor of \(W\) proved most accurate with a mean relative error (MRE) of 11.2%, while models incorporating additional dimensions (\(H\) and \(A\)) did not enhance predictive accuracy. Comparative analyses show our model aligns with some studies on tilapia, though variations in L-W relationships due to environmental and breeding conditions are evident. Our results affirm the utility of \({L}_{t}\) in non-invasive biomass estimation for aquaculture, while highlighting the limitations of applying these models universally across different conditions and fish populations. Condition factor (\(K\)) and relative condition factor (\({K}_{r}\)) analyses further demonstrated stable and optimal growth conditions (mean \(K\) ≈ 1.76; \({K}_{r}\) ≈ 1.01) for tilapia under local culture practices. Accordingly, we propose the L-W relationship \(W= {0.0265L}^{2.8469}\) for estimating the weight of gray tilapia grown in ponds with groundwater. This study provides a basis for the development of biomass estimation methods based on active acoustics or stereo video.