Why do fish and frog produce a huge number of eggs each year ?

Explanation

(1) Fish and frogs produce a large number of eggs each year because they undergo external fertilization.
(2) There is high risk in external fertilization and minimises the chances of fertilization of eggs due to external factors predators, high temperatures , water currents etc.
(3) Hence, it is necessary for them to produce a large number of eggs to improve their chances of fertilization.