Which fish can produce up to about 300 million eggs in a single spawning season?

The ocean sunfish can produce up to about 300 million eggs in a single spawning season.

This extraordinary reproductive output reflects the dangers faced by its offspring. Sunfish eggs and larvae are tiny and vulnerable to predators, currents and changing ocean conditions. Only a very small fraction survive to adulthood, so producing vast numbers increases the chance that some will mature.

The ocean sunfish, or mola, is the heaviest bony fish in the world. Adults have a flattened, almost circular body and a truncated rear fin called a clavus. They feed on gelatinous animals such as jellyfish, although their diet can also include small fish, squid and crustaceans.

The 300-million figure is a maximum estimate commonly associated with a large female, not a fixed number produced by every sunfish. Reproductive output varies with body size and condition.