Morphometric Traits of Old Blue <em>(Andinoacara rivulatus)</em> in Their Native Habitat and Aquaculture Environments: A Study of the Quevedo Region, Ecuador

A single paragraph of about 200 words maximum. For research articles, abstracts should give a pertinent overview of the work. We strongly encourage authors to use the following style of structured abstracts, but without headings: (1) Background: Place the question addressed in a broad context and highlight the purpose of the study; (2) Methods: briefly describe the main methods or treatments applied; (3) Results: summarize the article’s main findings; (4) Conclusions: indicate the main conclusions or interpretations. The abstract should be an objective representation of the article and it must not contain results that are not presented and substantiated in the main text and should not exaggerate the main conclusions. The Old Blue (Andinoacara rivulatus), an endemic freshwater species exclusive to Ecuador, represents a valuable resource for inland artisanal fisheries, yet limited information exists regarding its morphometric variation under different breeding conditions. This study aimed to compare morphometric characteristics between wild populations and those raised in fish farms within the Quevedo region of Ecuador. A completely randomized block design was applied with three factors: breeding system (wild and farmed), collection areas (Buena Fe, El Empalme, and Mocache), and sex (male and female), using 36 specimens (n=18 wild, n=18 farmed) and 16 morphometric measurement variables. Statistical analyses included Tukey’s test (p&lt;0.05), Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA), and Random Forest (RF) to evaluate significant differences and identify discriminant traits. Farmed individuals exhibited greater total, standard, ventral dorsum, and head lengths, with El Empalme showing the highest measurements among the areas, and farmed males presenting superior responses. The OPLS-DA model demonstrated a strong fit (R²Y=0.759, Q²=0.664, p&lt;0.05), while RF achieved 90.80% accuracy in distinguishing wild and farmed groups based on key morphometric traits. These findings provide a reliable framework for ecological studies and aquaculture management, supporting sustainable exploitation and conservation strategies for A. rivulatus in Ecuador.