Growth Pattern and Condition in the Mudskipper Scartelaos histophorus in the Mekong Delta

Studies of the length-weight relationship (LWR) and condition factor (CF) in fish are abundant but often descriptive; yet, most studies overlook how intrinsic and extrinsic drivers structure these metrics. Here, this study tested whether the growth exponent (b) varies across sex, season, and ecological region, and whether CF is elevated in females and before spawning. Over the course of a complete annual cycle, a total of 1436 individuals were collected from four mudflat sites, measured for total length (TL) and weight (W), and analyzed using log10-linear regressions of LWR and CF, along with appropriate parametric or non-parametric tests under false discovery rate control. The TL strongly predicted W (r ² = 0.87) with b = 2.46 ± 0.02 SE, (< 3; p < 0.001), indicating negative allometry. Females showed a larger size and higher b value (2.52) than males (2.41). The dry season yielded a higher b value than the wet season, and southern sites showed a non-significant trend towards a higher b value than northern sites. Mean CF was 1.01 ± 0.01 SE, elevated in females (1.09 vs. 0.98) and in the dry season (1.04 vs. 0.99), while monthly fluctuations (0.89-1.08) tracked feeding and reproduction but showed no regional differences. Overall, S. histophorus exhibits consistently negative allometric growth, with systematic variation in b and CF across sex and season. These findings provide hypothesis-driven baselines for monitoring semi-terrestrial gobies and highlight the importance of considering life-history and hydrological context when applying LWR/CF in ecological and evolutionary research and management.