A global shark census has reached its first 100 reefs, revealing early findings that suggest existing data on shark populations may be inaccurate.

The census, led by the University of Oxford, aims to create the most comprehensive picture yet of the world's shark populations. Researchers are conducting surveys at 500 reefs in 58 countries, using baited remote underwater video systems (BRUVS) to record the presence and abundance of sharks.

The early findings have revealed several surprises. For example, the researchers have found that shark populations are often much larger than previously thought. On some reefs, they have recorded up to 10 times more sharks than previous surveys had suggested.

The researchers have also found that the distribution of sharks is different from what was previously thought. For example, they have found that some shark species that were thought to be rare are actually quite common.

The findings of the shark census have important implications for the conservation of sharks. The researchers say that the existing data on shark populations is not accurate enough to make informed decisions about conservation measures. They say that the census will provide much-needed data to help protect these important predators.

"Our findings so far suggest that we may need to rethink our conservation strategies for sharks," said Professor David Sims, who is leading the research. "We need to make sure that we are protecting the right species in the right places."

The shark census is a major undertaking that will take several years to complete. However, the early findings are already providing valuable insights into the world's shark populations. The researchers hope that the census will ultimately help to protect these important predators from extinction.