Evaluation of Well-Being Status of Near-Threatened Gangetic Leaf Fish Nandus nandus (Hamilton, 1822) in the Kawadighi Haor: Implications to Haor Fishery Management in the Northeastern Bangladesh

Abstract

This study evaluated the status of the well-being of wild Nandus nandus in the Kawadighi Haor through morphometric and gastrointestinal indices and local people’s perceptions. Basic macroscopic morphology of the gastrointestinal tract (GIT), the viscera somatic index (VSI), the hepatosomatic index (HSI), the condition factor (K), length–weight relationships, and gut histology were analyzed from the regular commercial catch. The GIT morphology includes a tube-like esophagus, a tapering stomach, a tubular intestinal region, and a rectum, all of which have clinically normal shapes and conditions. VSI and HSI values fluctuate throughout the year, indicating the periodic variation of food content and availability in the ecosystem. The condition factor (K) was generally stable, with minor deviations in December. The mucosa, submucosa, muscularis, and serosa were identified from the stomach of N. nandus and showed normal histological characteristics. There were numerous proliferated villi in the tunica mucosa, but no histopathological abnormalities were found in the gut. These findings suggest that the current population of N. nandus in the Haor is in a favorable condition. However, local people reported some potential threats that might be a concern for the long-term survival of this species. The results of the present study will be useful for effective and sustainable stock management of the N. nandus fishery in the Kawadighi Haor and other floodplain ecosystems.