SOME TRAITS OF THE DIGESTIVE TRACT AND RELATIVE GUT LENGTH INDEX OF Butis butis (HAMILTON, 1822)

Abstract

This study contributed some digestive tract characteristics and the variation of the relative gut length index (RGL) concerning sex, season, and sampling site of Butis butis (Hamilton, 1822). The analysis results of 715 specimens (412 males and 303 females) collected at Duyen Hai - Tra Vinh (TV), Tran De - Soc Trang (ST), Hoa Binh - Bac Lieu (BL) and Dam Doi - Ca Mau (CM) showed that this species had a slightly sloping mouth, its jaw consisted of two teeth line and the outer teeth row were more significant than the inner one. The relative gut length (RGL=0.48±0.01 SE) of this species was lower than 1 (t-test, t=-0.52; p<0.001). This showed that this goby was a carnivore. The RGL of males (0.46±0.01 SE) was lower than that of females (0.50±0.01 SE; t=6.46; p<0.001), but this value in the dry season (0.49±0.01 SE) was similar to that in the wet season (0.48±0.01 SE; t=0.43; p=0.67). The RGL varied with the sampling site, reaching the highest value in CM (0.50±0.01 SE) and the lowest in BL (0.47±0.01 SE) and ST (0.48±0.01 SE) (1-way ANOVA; F=3.70; p=0.01). The RGL also changed with the month (F=3.04; p=0.01) and the interaction of sex × season (2-way ANOVA; F=12.95, p<0.001) and season × sampling site (F=3.28; p=0.02). The findings contributed to further understanding of fish nutritional characteristics of B. butis.