At the beginning of finding nemo movie what happened to family?

In the beginning of Finding Nemo, Marlin and Coral, a clownfish couple, are preparing to have their eggs hatch. However, a barracuda attacks the reef, killing Coral and all but one of their eggs - Nemo.

Marlin, traumatized by the event and terrified of losing his only remaining child, is extremely overprotective of Nemo. This sets the stage for the film's plot as Nemo's adventurous spirit leads him to be separated from his father, prompting Marlin's journey to find him.