| dc.description.abstract | The present research was conducted to find out the monthly variation of gut fauna and flora of
Meni fish (Nandus nandus) in Kawadighi haor of Sylhet division from January to December
2014. Different aspects of alimentary canal were assessed macroscopically. Gut content and
histological analysis of gut were observed microscopically. From the histological analysis,
Intestinal wall was composed of the tunica mucosa, tunica submucosa, tunica muscularis and
tunica serosa. The tunica mucosa had many folds known as villi. The mucosal epithelium was
composed of enterocytes with brush border. The mouth cavity of N. nandus was sac like
elongated structure. Oesophagus was observed comparatively smallest part of the alimentary
canal. Stomach was well developed, tapering and nipple form. The intestine was more or less
coiling in pattern. Fish length and weight were strongly positively co-related (R
=0.918) means
that the total length increased significantly with the increasing of total weight. The highest value
of VSI was observed at June (5.18±0.25) and lowest at October (1.86±0.12). The maximum
value of HSI was observed at June (2.49±0.45) and minimum at October (1.07±0.23). The
average total length was 1.06 times greater than intestinal length of fish. The intestinal length
was 3.92 times greater than that of stomach. Three groups of phytoplankton were found in the
gut content of N. nandus. They were Bacillariophyceae (2 genera), Chlorophyceae (6 genera),
and Cyanophyceae (2 genera). Three groups of zooplankton belonging to Crustacea (9 genera),
Rotifera (6 genera) and fish and insects larvae were recorded from the guts. Among various
groups of phytoplankton, Chlorophyceae was observed highest in abundance. Among the
zooplankton, Crustacea was dominant group. The average amount of stomach content was higher
in March, July, and September compared to other months of the year. There was no empty
stomach found over the study period. The research work drew a conclusion that N. nandus fed on
both phytoplankton and zooplankton but showed highest preference for zooplankton.
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