Two different reef shark species in one shot: a juvenile nurse shark (Ginglymostoma cirratum) (left) and Caribbean reef shark (Carcharhinus perezi) near bated camera - used for quantitative assessment. Credit: Institute for Ocean Conservation Science.

After some good news about blue whales perhaps now there is also something hopeful to say about sharks.

That however would still depend on whether we will be able to create and maintain protected areas in tropical reef systems along different continents and island groups.

As we earlier reported for the Mediterranean Sea such marine reserves manage to maintain much larger biodiversity in general – and as a different PLoS ONE publication showed last year, in Australian waters that goes for sharks specifically as well, as there the number of reefs sharks recovers in reserves.

What works for the one reef system works for the other

The new research – also published in PLoS ONE – was led by the Institute for Ocean Conservation Science at Stony Brook University. These scientists have focused on reef sharks in the Caribbean Sea and have discovered – using bated underwater cameras to carry out a quantitative assessment – that there too shark numbers are higher (‘than expected’) in protected reef ecosystems.

So once again we learn conservation is effective [but mostly lacking].

Not all sharks are shy

Protection of reef systems is of course of crucial importance to slow down our planet’s general biodiversity decline. Reef sharks are a group that may profit, but that is not to say of sharks in general.

The authors of the new study conclude ‘individual reef sharks exhibit high site-fidelity to these protected areas.’ Larger shark species however like to swim around across the open oceans as well.

And unless the international community manages to establish very large enforced non-fishing areas, the decline of these sharks is largely left unabated. Although we could of course just clamp down on the fin soup market – the world’s most ecologically unfriendly food industry and associated consumer group. How hard can it be to switch to any of about a million less harmful foods?

Predators are more than indicators of biodiversity

Just like large carnivores on land the marine apex predators, including many whales and sharks are important for ecosystem health. Different studies show that larger shark numbers actually contribute to larger overall biodiversity, mostly because the presence of a sufficient number of large predators prevents dominance of single (herbivorous) species.

As we’ve seen for the East Mediterranean under dominance of herbivores plant biodiversity generally tends to decline, which has cascading consequences in all directions of the food chain and speeds up faunal diversity decline as well.

© Rolf Schuttenhelm | www.bitsofscience.org