Reproduction, Dispersal, and Migration
The goal of reproduction for any organism is to pass its hereditary characteristics on to a new generation. There is a nearly endless variety of ways to achieve this. Some species release millions of eggs and sperm into the water, where fertilization occurs, and have no further interaction with their offspring. This is called broadcast spawning. Others issue only a few offspring and invest a lot of time and energy in caring for them. Some species have many different larval stages, whereas others develop directly from egg to adult. Some reproduce asexually, some reproduce sexually, and some do both.
Dispersal is the mean for organisms that depend on being the first to occupy new patches of open space must be good at getting themselves or their offspring from place to place. Most rocky intertidal species disperse via larvae or spores, which settle on the rocks to colonize open space. Another fascinating aspect of the behaviour of marine fishes is Migration, regular mass movements from one place to another once a day, once a year, or once in a lifetime. Schools of parrot fishes and other fishes migrate onshore and offshore to feed. Many open-water fishes migrate several hundred meters up and down the water column every day.