Final answer:
Bangladesh hosts a rich biodiversity due to its fertile river deltas, and while it's certain that a large number of fish species inhabit its waterways, exact numbers require detailed research.
Step-by-step explanation:
The number of fish species in Bangladesh is vast, as the country's waterways, including the Ganges and Brahmaputra river deltas, support a rich biodiversity. Fish sustains a significant part of the Bangladeshi diet, providing essential protein to many citizens.
Notably, some fish species like the Mozambique Tilapia (Oreochromis mossambicus) and Grass Carp have been introduced globally, with Bangladesh being one of the many countries that house these species.
Regrettably, exact figures detailing the total number of fish species in Bangladesh require more specific research and exploration, due to constant ecological changes, potential new discoveries, and the presence of both native and introduced species.