Digestive Tract Morphology and Relative Gut Length Index of Polynemus melanochir Valenciennes, 1831 in Cai Rang, Can Tho, and Long Phu, Soc Trang

The study provided the digestive tract morphology, relative gut length (RGL), and variation of this index regarding sex, season, and sampling site of the Polynemus melanochir. The analysis results of 308 fish samples (119 males and 189 females) collected from Cai Rang - Can Tho and Long Phu - Soc Trang showed that this fish displayed a wide mouth and differences based on the interaction of sex × size (ANOVA, df=1; F=4.58, p=0.03). The relative gut length (RGL=0.48±0.01 SE) falls into the group of carnivores as RGL<1 (t-test, df=306; t=-2.34; p>0.001), so that this fish species belongs to the carnivore group. Differences in RGL were also noted among sampling site and sex, with males (0.50±0.01 SE) having a larger RGL than females (0.48±0.01 SE; t-test; df=306; t=0.10; p>0.001). These results have supplemented additional information regarding the nutritional characteristics of this species, and being used as a basis for understanding the ecological adaptation of this species to its habitat and as a foundation for further research on artificially raising them.