Dangerous demographics: the lack of juvenile humphead parrotfishes Bolbometopon muricatum on the Great Barrier Reef
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The humphead parrotfish, Bolbometopon muricatum, the largest of all parrotfish species, is heavily fished throughout most of its range. In remote and heavily protected locations, such as the Great Barrier Reef (GBR), it is a major component of parrotfish biomass and plays a critical role in ecosystem processes. However, extensive surveys of GBR populations have revealed a striking lack of juveniles. Of 633 individuals censused, just four were juveniles. This represents 0.6% juveniles and contrasts markedly with the 20.2–40.2% juveniles recorded in eight other medium to large parrotfish species. These low values in Bolbometopon are corroborated by over 5,000 h of independent observations and extensive museum collections. Whilst there is no evidence to suggest that this is an extraordinary new condition for GBR Bolbometopon, it may nevertheless expose them to special risks in a changing and unpredictable world. Despite excellent management on the GBR, Bolbometopon populations may be more vulnerable than previously thought.
KeywordsBolbometopon Demographics Coral reefs Fishing pressure Population structure Labridae
We thank A. M. Ayling, A. Barnett, M. Depczynski, A. S. Hoey, M. J. Marnane, R. J. Fox, C. J. Fulton, and S. Wismer for field assistance and help with data collection; the staff of Lizard Island and Orpheus Island Research Stations for field support; J. Tanner for assistance with manuscript preparation; colleagues in the reef fish lab and Centre of Excellence for helpful discussions; N. Dulvy and two anonymous reviewers for insightful and constructive comments, and the Australian Research Council and Great Barrier Reef Marine Park Authority for financial support (DRB).
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