Improving von Bertalanffy growth parameters and natural mortality estimates in Brama australis (Valenciennes, 1838) using larval hatch size

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Abstract

Accurate von Bertalanffy growth parameters (VBGP) are critical for fisheries assessment, but they are often biased by the absence of juvenile data, leading to errors in their estimation and derived variables such as natural mortality (M). This study re-estimates the VBGP and M in Brama australis, a commercially important fish resource in Chile. To correct this, a larval hatch size (L₀) was incorporated as a fixed "biological anchor point" (BAP) to constrain the von Bertalanffy growth function and mitigate extrapolation errors in theoretical age at zero length (t₀). We re-estimated growth parameters from three previous studies using a phylogenetic proxy for L₀ (Brama japonica, 0.48 cm). The method consistently produced revised parameters across all studies, converging to a pooled average of L_∞ = 56.17 cm, k = 0.32 yr^-1, and t₀ = -0.03 years, indicating faster growth and a biologically plausible t₀ compared to original estimates. This correction directly resulted in a higher and more precise estimate of M, which increased to a narrowed range of 0.48-0.50 yr^-1 from an original 0.39-0.47 yr^-1. The revised parameters showed a markedly improved fit to Beverton and Holt's life-history invariants, reducing the total absolute mean difference from theoretical values from 64 to 3.4%. Our results demonstrate that the methodology used generated more realistic growth models and robust M estimates, providing essential corrections for stock assessment models and management of this fishery.

Leal, E., Moyano, G., Gatica, C., & Gálvez, P. (2026). Improving von Bertalanffy growth parameters and natural mortality estimates in Brama australis (Valenciennes, 1838) using larval hatch size. Latin American Journal of Aquatic Research, 54(4), 683-692. doi:http://dx.doi.org/10.3856/vol54-issue4-fulltext-3555

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