Reef fish spawning aggregations, ranging from small groups to many tens of thousands of individuals, are spectacular but poorly known natural phenomena whereby fish assemble at specific times and locations to spawn. For some species these large groups may be the only form of reproduction, the high fish numbers briefly giving a false impression of stability and abundance-an 'illusion of plenty'. They are often a focus for intensive seasonal fishing because of their predictability and because many important commercial fishes form them. Highly vulnerable to overexploitation, many aggregations...

Reef fish spawning aggregations, ranging from small groups to many tens of thousands of individuals, are spectacular but poorly known natural phenomena whereby fish assemble at specific times and locations to spawn. For some species these large groups may be the only form of reproduction, the high fish numbers briefly giving a false impression of stability and abundance-an 'illusion of plenty'. They are often a focus for intensive seasonal fishing because of their predictability and because many important commercial fishes form them. Highly vulnerable to overexploitation, many aggregations...