A study published in the Public Library of Science (PLoS) ONE journal confirms that there is statistical and scientific evidence that shark populations are experiencing “widespread, substantial, and ongoing declines”. The authors of the report have developed several alternative models to quantify shark populations, which combine birth and growth rates for sharks with a variety of different methods for estimating mortality. They then used state-of-the art statistical methods to combine the uncertainty associated with each of these methods and arrive at a robust long-term population prediction for two Great Barrier Reef shark species, the grey reef shark and the whitetip reef shark.
The researchers used their population projections to see how well their models could explain differences in shark abundances between fished and unfished reefs, based on how long the unfished reefs had been protected. The results showed that shark populations are declining rapidly due to fishing.