Biology of the endangered queen loach (Botia dario) collected from wild sources in Bangladesh

The study was conducted with the aim of evaluating the food and feeding habit of Botia dario, collected from wild sources of north-eastern Bangladesh from January to June 2019, by calculating the: Gastrosomatic Index (GaSI), Relative Gut Length (RGL), Gonadosomatic Index (GSI) and Hepatosomatic Index (HSI). Food and feeding habit were evaluated based on the gut content analysis followed by the percent of numerical method and the frequency of occurrence method. Observation of feeding habit of Botia dario revealed that it is a carni-omnivorous and bottom feeder fish having a preference for animal materials (89.06%) over plant materials (2.67%). By percent of numerical method, the main contributors to their diet were worms (46.40%), followed by fish particles (28.80%), crustaceans (5.60%), insects (5.33%), detritus (3.20%), molluscs (2.40%), algae (1.87%), plant parts (0.80%) and water mites (0.53%). By frequency of occurrence method, worms and fish particles had a similar contribution (94.44%) to B. dario diet, followed by insects (66.67%), crustaceans (55.56%), algae (38.49%), detritus (33.33%), molluscs (22.22%), plant parts (16.67%) and water mites (11.11%). Average RGL value of B. dario was 1.08±0.16 which also demonstrates the carni-omnivorous nature of the species. Maximum GSI value was found in the month April (11.29±1.53), and HSI value was lowest in April for both female (1.69±0.77) and male (1.85±0.18). The highest GSI value and lowest HSI values in April indicate that it is the spawning period for this species, because the liver has a weight loss during reproduction which may imply the mobilization of the hepatic reserve for the maturation of gonads. Moreover, the lower RGL (0.98±0.03) and GaSI (0.91±0.56) values in April indirectly confirmed that April is the spawning period for B. dario. The findings might be useful as baseline information on the biological characteristics of B. dario.