What are some factors that prevent the majority of these eggs from developing intonfish then reproduce on their own?

There are several factors that prevent the majority of fish eggs from developing into fish and reproducing on their own:

Predation: Fish eggs and larvae are a food source for a variety of predators, including other fish, birds, insects, and aquatic mammals. Many fish eggs are consumed before they have a chance to hatch.

Environmental conditions: Fish eggs are sensitive to environmental conditions such as temperature, pH, and oxygen levels. If these conditions are not optimal, the eggs may not hatch or the larvae may not survive.

Disease: Fish eggs and larvae can be infected by a variety of diseases, which can cause them to die.

Competition: Fish larvae compete with each other for food and resources. The strongest and most adaptable larvae are more likely to survive and reproduce.

Genetic factors: Some fish eggs may not be viable due to genetic defects. These eggs will not hatch or the larvae will not survive.

As a result of these factors, only a small percentage of fish eggs actually survive to adulthood and reproduce. This is why it is important for fish populations to produce a large number of eggs in order to ensure the survival of the species.