How do fish reproduce

For some time I have been thinking of writing a how do fish post a week, but have never really gotten around to it. I plan to cover a range of topics including how do fish reproduce (todays topic), hear, smell and many more. If you like (or hate) the idea feel free to leave a comment.

How do fish reproduce
While there are exceptions to the rule most fish reproduce in a similar fashion. In over 97% of fish species the eggs develop outside the mothers body. The male fish then fertilizes these eggs in the open water and they are left to hatch.

The newly-hatched young are called larvae. Usually they are poorly formed and carry a large yolk sac, which they use for food. At this stage they will look very different from the adult fish and are susceptible to predators. This period lasts for a few weeks during which the larvae grow and change their appearence and structure to resemble a juvenile fish. At this stage the fish will swich from feeding on the yolk sac to feeding on zooplankton prey.

In about 3% of the fish species the mother retains the eggs and internal fertilization takes place.