The commercial culture of several important species of fish has long been associated with productivity problems generally attributable to fertilisation rates, hatching rates, and embryonic development. Our present knowledge of the molecular processes accompanying fertilisation in fish is scant at best. Here, we examine how new findings about the molecular mechanisms underlying reproduction in other animal groups may help advance our understanding of how egg activation takes place in fish. A better understanding of egg activation in fish is likely to make a highly valuable contribution to future growth of the aquaculture industry.