The scientists studied populations of the bicolour damselfish (above), a species found commonly on Caribbean coral reefs that has a 30-day larval stage. They sampled newly settled juvenile fish at sites in Belize and Mexico and then traced the origins of hundreds of individual fish larvae back to their putative source populations.

‘This is the first time that genetic “assignment tests” have been used to delineate the pattern of connectivity for a marine fish in a region of this size (approximately 6,000 square kilometres),’ said the study’s lead author, Derek Hogan of the University of Windsor in Ontario.

They found that the larvae travelled, on average, 77 kilometres before settling, although some remained close to home and others travelled almost 200 kilometres. Interestingly, the patterns of larval dispersal among reefs changed from year to year, more than likely driven by changes in ocean currents.

‘These studies are invaluable for understanding how to design networks of MPAs effectively,’ said Hogan. ‘The functioning, and therefore the success, of networks of MPAs designed for conserving species depends fundamentally on our deep understanding of larval migrations.’

September 2011