Abstract <p>To understand the impact of morphological traits at different growth stages on the body weight of largemouth bass <i>Micropterus salmoides</i>, key morphological traits and the body weight were measured for 4-, 6-, and 8-month-old fish. We determined coefficients of correlation, path, and determination for each trait in relation to the body weight. Path analysis showed that total length had the most significant direct effect on the body weight, with coefficients of 0.735, 0.725, and 0.568 for 4-, 6-, and 8-month-old fish, respectively. Body height had the most pronounced indirect effect on the body weight for 4- and 6-month-old fish, with coefficients of 0.744 and 0.706. For 8-month-old fish, body width had the most significant indirect effect, with a coefficient of 0.734. Regression equations were established with total length, body height and width as independent variables and the body weight as the dependent variable. The <i>R</i>² of the regression equations exceeded 0.85, highlighting total length, body height and width as significant indicators affecting the body weight. The three morphological traits of total length, body height and width in the three growth stages were fitted with the the body weight curve model, and the optimal fitting curve models were selected according to the <i>R</i>² and F values. Thus, in breeding largemouth bass aged 4 to 8 months, total length should be prioritized as the primary breeding trait, with body height and width as supplementary traits. These findings provide a theoretical basis for breeding largemouth bass with a focus on body weight.</p>