Correct option is B
India holds the second position globally in freshwater fish production, following China. This is largely due to the country's expansive inland water resources, which support a thriving aquaculture industry. Fish farming in India, particularly the production of freshwater species like carp, has been an essential contributor to the country's fish production.
Assertion (A) is correct: India ranks second in freshwater fish production due to its strong aquaculture industry and the promotion of fish farming.
Reason (R), however, is not entirely accurate. While India has a diverse range of fish species, the number of species is significantly less than 18,000. Estimates suggest that the country has around 2,400 species of fish, including both freshwater and marine species. Thus, the reason does not correctly explain the assertion.