Otolith morphology, position, and size-body relationships in Periophthalmodon schlosseri (Gobiiformes: Oxudercidae) from Bac Lieu, Vietnam

Periophthalmodon schlosseri, a common mudskipper in estuarine and coastal areas of the Mekong Delta, plays an important ecological and economic role. While various biological aspects of this species have been studied, data on its otolith morphology remain lacking. This study examined the morphological characteristics of sagittal otoliths and their relationship with fish size in 200 specimens (110 females, 90 males) collected in Bac Lieu Province, Vietnam, from October 2024 to March 2025. Fish were captured using baited traps and burrow flushing techniques. Using digital imaging software, otoliths were extracted, weighed, and measured under a stereomicroscope. Results indicated values of otolith length, width, and weight were relatively similar between the left (OL = 5.58 ± 0.58 mm, OW = 4.88 ± 0.52 mm, WO = 25.64 ± 6.92 mg) and right (OL = 5.59 ± 0.57 mm, OW = 4.92 ± 0.52 mm, WO = 25.62 ± 7.09 mg) sides. Otolith parameters exhibited strong positive correlations with total length and body weight, with otolith weight showing the highest predictive value (r2 > 0.68). These findings provide the first baseline data on otolith morphology for P. schlosseri, representing the first description for this species within the Mekong Delta, while complementing previous reports in other teleost fishes. The study contributes to the broader understanding of otolith-based applications in fish biology and supports future fisheries research in the Mekong Delta region.