A reef fish spawning aggregation is a grouping of a single species of reef fish that has gathered together in greater densities than normal with the specific purpose of reproducing.

The best-known examples are certain species of grouper and snapper, although there are also surgeonfish, rabbitfish, parrotfish and wrasse and others that form them. There is a great deal of variability among different species in the dynamics of aggregation formation. For instance, spawning aggregations of some small wrasses may consist of just ten individuals spawning close to their normal home range on the reef, while those of some large groupers consist of tens of thousands of fish that may have travelled over one hundred kilometres to the aggregation site on a particular reef.

There is one feature, however, shared by all reef fish spawning aggregations, and that is that they typically form at the same place and at approximately the same times each year.

There is much to know about spawning aggregations so we have prepared a list of questions that commonly arise (see FAQs), or issues that are sometimes not fully understood or appreciated.