Morphometric Relationships, Condition Indices and Size‐Dependent Morphometric Shifts in Four Lobster Species From Southeastern Brazil

ABSTRACT Reliable morphometric relationships are essential for integrating fisheries datasets collected under different sampling protocols, yet regional information remains scarce for several commercially exploited Brazilian lobsters. We quantified species‐ and sex‐specific morphometric relationships for four commercially important lobster species landed by small‐scale fisheries along the southern coast of Espírito Santo, southeastern Brazil. A total of 802 individuals, sampled between April 2020 and March 2025, were measured for total length (TL), cephalothorax length (CL), cephalothorax width (CW) and total weight (TW). Analytical sample sizes varied among species, sexes and models according to data availability and quality‐control procedures. Length–weight and length–length relationships were estimated for each species and sex, condition indices were evaluated and segmented regression was used to investigate size‐dependent changes in morphometric scaling. Length–weight models explained a large proportion of the observed variation across species ( R 2 = 0.81–0.99), providing reliable empirical conversion equations for fisheries monitoring. Significant sex‐specific differences in morphometric scaling were detected for Panulirus laevicauda and Panulirus meripurpuratus , whereas relationships were generally similar between sexes in Scyllarides brasiliensis . Relative condition factor ( K n) showed little evidence of systematic size dependence and was considered more appropriate than Fulton's condition factor for biological comparisons among individuals of different sizes. Segmented regression supported size‐dependent changes in morphometric scaling only in P. laevicauda , whereas linear relationships adequately described the remaining species. Owing to limited sample size, results for Panulirus echinatus should be interpreted as descriptive. These relationships provide a robust regional reference for converting morphometric measurements, estimating body weight, providing standardized regional biometric parameters for fisheries monitoring and future biological assessments of small‐scale lobster fisheries.