The knowledge about the weight, length and condition factor of the organisms is key for explaining the population dynamics in wild animals. The present study was focused on finding the model that best explains the length-weight relationships in epibenthic and juveniles of Farfantepenaeus duorarum, as well as the condition factor during the different months sampled. In the study, 3 992 individuals (size range: 3.62-32.16 mm cephalothorax length) were collected from three different places at the Terminos Lagoon from May 2011 to March 2012. The individuals were grouped into three sex categories: male (M), female (H), and undefined (I), and their length-weight (L-P-1) relationship, as well as their relative condition factor, were determined. The results indicate that the total length-carapace length (LT-LC) relationship for each sex category was linear, there was no difference between the models for small males and females and the relationship can be expressed as (LT (M-H) = 1.89 + 4.46 LC). For the undefined group, the relationship was different and is best expressed as LT (I) = 0.07 + 4.62 LC. The potential model for the expression of Carapace Length-Weight in the M-H group was P = 0.0016 LC2.5323 or log (P) = 2.5323 log(LC) - 2.8079, R² = 0.9272 in the linear model. In the undefined group, the potential model was W = P = 0.0004LC3.2315 and the linear model was log (P) = 3.2315 log(LC) - 3.4365, R2 = 0.9422. On the other hand, the relative condition factor (Kn) differed among groups when the date was involved in the analysis. We consider that relative condition factor involving Total Length is better than relative condition factor including Carapace Length to measure population characteristics of shrimps and that index could contribute to evaluating the shrimp population dynamics.

Keywords: biometry, sex, breeding area, population dynamics, Campeche