Characterization of giant mottled eel (Anguilla marmorata) gastrointestinal tract that origin from Thua Thien Hue, Vietnam

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Characterization of giant mottled eel (Anguilla marmorata) gastrointestinal tract that origin from Thua Thien Hue, Vietnam

This study investigated the dietary component and morphology of the digestive tract of Anguilla marmorata during its yellow stages (non-migrants). A total of 127 samples, ranging in total length from 17-108 cm and weight from 10-3200 g were collected from Thua Thien Hue, Vietnam. The structure of the gastrointestinal tract indicated that Anguilla marmorata has the typical characters of carnivorous fish such as a wide mouth, small teeth in bands; free tongue; short esophagus, stomach, and intestines made up of folds. The mouth size of Anguilla marmorata ranged from 1.81-6.6 cm and it increased with the body weight of fish. Anguilla marmorata is an animal-eating species with an RLG (relative length of the gut) ranging from 0.34 to 0.41 (RLG <1). Crustacea is the preferred food of eels with the highest proportion of the number, weight, and frequency of crustaceans in the gastrointestinal tract with 65%, 64%, and 80%, respectively. Crustacea was also the most important food of Anguilla marmorata in the wild with the index of relative importance (IRI%)=79%. Correlation equation between length (L=17- 108 cm) and weight (W=10-3200 g) of Anguilla marmorata is L=9.948W0.0622 with correlation coefficient R2 =0.93. Our report provides new dietary information about A. marmorata that is useful in nutrition planning and aquaculture potential.

Morphological characteristics of the gastrointestinal tract show that Anguilla marmorata is a carnivorous fish. They have a long and pointed mouth, the sharp of teeth look like a dog arranged on two jaws and the main oral bones and free tongue. The eel has a large mouth size, varying by body weight. The larger the fish, the larger the size of the mouth. The size of the mouth of eel ranged from 1.81 to 6.6 cm in the mass range of 10-3200 g.

The stomach and intestines of Anguilla marmorata are short, with many folds having great elasticity. The RLG value of Anguilla marmorata fluctuates between 0.34 and 0.41 and less than 1, which is characteristic for fish-eating species.

The eel's natural feed ingredients include crustaceans, fish, mollusks, and other species. Crustaceans are the most abundant species in the gastrointestinal tract, with 68% of the number, 64% of weight, 80% of frequency and 79% for IGI% index.

Correlation equations between length (L=17-108 cm) and weight (W=10-3200 g) from 127 individuals in this study of Anguilla marmorata were L=9.948W0.0622 with correlation coefficient R2=0.9083 indicating a strong correlation between length and weight. The growth rate of the length tends to decrease with the increase in body weight.

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