The whale shark is an ideal flagship species for citizen science projects because of its charismatic nature, its size, and the associated ecotourism ventures focusing on the species at numerous coastal aggregation sites. An online database of whale shark encounters, identifying individuals on the basis of their unique skin patterning, captured almost 30,000 whale shark encounter reports from 1992 to 2014, with more than 6000 individuals identified from 54 countries. During this time, the number of known whale shark aggregation sites (hotspots) increased from 13 to 20. Examination of photo-identification data at a global scale revealed a skewed sex-ratio bias toward males (overall, more than 66%) and high site fidelity among individuals, with limited movements of sharks between neighboring countries but no records confirming large, ocean basin-scale migrations. Citizen science has been vital in amassing large spatial and temporal data sets to elucidate key aspects of whale shark life history and demographics and will continue to provide substantial long-term value.

BRADLEY M. NORMAN, JASON A. HOLMBERG, ZAVEN ARZOUMANIAN, SAMANTHA D. REYNOLDS, RORY P. WILSON, DANI ROB, SIMON J. PIERCE, ADRIAN C. GLEISS, RAFAEL DE LA PARRA, BEATRIZ GALVAN, DENI RAMIREZ-MACIAS, DAVID ROBINSON, STEVE FOX, RACHEL GRAHAM, DAVID ROWAT, MATTHEW POTENSKI, MARIE LEVINE, JENNIFER A. MCKINNEY, ERIC HOFFMAYER, ALISTAIR D. M. DOVE, ROBERT HUETER, ALESSANDRO PONZO, GONZALO ARAUJO, ELSON ACA, DAVID DAVID, RICHARD REES, ALAN DUNCAN, CHRISTOPH A. ROHNER, CLARE E. M. PREBBLE, ALEX HEARN, DAVID ACUNA, MICHAEL L. BERUMEN, ABRAHAM VÁZQUEZ, JONATHAN GREEN, STEFFEN S. BACH, JENNIFER V. SCHMIDT, STEPHEN J. BEATTY, AND DAVID L. MORGAN