Morphological Characterization of Giant Mottled Eel (Anguilla marmorata) Gastrointestinal Tract that Origin from Thua Thien Hue, Vietnam

The food composition and anatomy of the digestive tract of Anguilla marmorata during its yellow stages were studied in this study (non-migrants). Anguilla marmorata is also widely dispersed, exploited, and farmed as a high-value crop. A total of 127 samples were gathered from Thua Thien Hue, Vietnam, with total lengths ranging from 17 to 108 cm and weights ranging from 10 to 3200 g. Anguilla marmorata features the typical characteristics of carnivorous fish, such as a broad mouth, small teeth in bands, a free tongue, a short oesophagus, stomach, and intestines made up of folds, according to the nature of its gastrointestinal tract. The mouth size of Anguilla marmorata ranged from 1.81 to 6.6 cm, and it grew in proportion to the fish’s body weight. Anguilla marmorata is a carnivorous species having an RLG (relative length of the gut) of 0.34 to 0.41 (RLG 1). Crustacea is the preferred food of eels, with 65 percent, 64 percent, and 80 percent of the quantity, weight, and frequency of crustaceans in the gastrointestinal tract, respectively. Crustacea was likewise Anguilla marmorata’s most significant diet in the wild, with an index of relative importance (IRI percent) of 79 percent. L=9.948W0.0622 with R2=0.93 is the correlation equation between length (L=17-108 cm) and weight (W=10-3200 g) of Anguilla marmorata. Our study adds to the body of knowledge on A. marmorata’s food habits, which can help with nutrition planning and aquaculture potential.

Author (S) Details

Kieu Thi Huyen

Faculty of Fisheries, University of Agriculture and Forestry, Hue University, Thua Thien Hue, Hue City 530000, Vietnam.

Nguyen Quang Linh

Department of Nutritional Diseases and Systems for Livestock and Aquaculture, Institute of Biotechnology, Hue University, Thua Thien Hue, Hue City 530000, Vietnam.

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Effects of Height of F2-Layer on Critical Frequency at Low Latitudes Using Data and a Numeric Model

Ionosphere investigation leads to the knowledge of its composition in particles. The density in
particles determines the capacity of this region to reflect radio waves in the atmosphere at different
heights. Some variables such as season and solar cycle phase also influence the ionosphere
behavior. Radio waves frequencies pass through the ionosphere layer without reflection above a
critical value determining the critical frequency. The density in particles in this region is variable from
daytime to nighttime and during the seasons of the year. The solar cycle phases also influence the
composition in particles of ionosphere region.
Many models are developed to give a good approach of ionosphere region. Some of them are
mathematical simulations. A good model must match with data results of parameters.
This study determines, in first time, the critical frequency of radio waves in the F2 layer (foF2) of the
ionosphere by use of data during the minimum and the maximum of solar cycle 22, at different
seasons with the height of F2-layer (hmF2). It presents the hourly behavior of foF2 according to hmF2
values. In second time, Thermosphere-Ionosphere-Electrodynamics General Circulation Model
(TIEGCM) is used to give an approach for ionosphere description. TIEGCM has been developed at
National Center for Atmospheric Research (Boulder, Denver, Colorado State, USA). This model is
used to carry out the Critical frequency of F2-layer and the Height of F2-layer in ionosphere. Local
time links these parameters during quiet time periods for solar cycle 22. The study takes place at
Ouagadougou station, in West Africa, near equator. The study also proposes a new approach to
evaluate the annual values of these parameters. It gives good correlation with the results found by
running other models such as International Reference Ionosphere (IRI) model in the same conditions.

Author (s) Details

Emmanuel Nanéma
Centre National de la Recherche Scientifique et Technologique (CNRST), Institut de Recherche en Sciences Appliquées et Technologies (IRSAT), 03 BP 7047 Ouagadougou 03, Burkina Faso.

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