How well do marine protected areas truly protect highly migratory sharks?

The designation of an area of ocean as a marine protected area will be a cause of celebration for most conservationists; restricting fishing activity within a certain area takes pressure off fish stocks and benefits the ecosystem. However, many marine protected areas (MPAs) are created with a certain goal - often to protect coral reefs or specific resident species. Highly migratory species such as sharks would only benefit from the protection an MPA offers when they are residing within the MPA zone. A team of researchers at University of Miami have been investigating how much time 3 key shark species spend within the MPA designated zones around Florida and the Bahamas in order to ascertain the true level of protection these species enjoy.

Over the course of 4 years the researchers satellite tagged tiger (Galeocerdo cuvier), bull (Carcharhinus leucas) and great hammerhead (Sphyrna mokarran) sharks within the study area. The study area contained a mixture of national parks, economic exclusion zones (EEZ) and a national marine sanctuary which included a no-take zone. In addition to this, shark harvesting has been entirely prohibited in the Bahamas since 2011, when a shark sanctuary was created. Within Florida state waters it is not permitted to take tiger, great hammerhead, scalloped hammerhead (Sphyrna lewini) or smooth hammerhead (Sphyrna zygaena) sharks and the maximum catch for all other shark species is one shark per person per day. This study also included parts of the US EEZ which has more relaxed laws than Florida state waters and allows up to 36 large sharks per boat per day to be removed.    

The researchers discovered that none of the core habitat use by the bull sharks tagged in this study overlapped with any of the areas which would have afforded them complete protection. For the great hammerhead, 27% of their core habitat range fell within protected, no-take regions and for tiger sharks it was 34.74%. These figures show that, despite there being several regions where shark fishing is completely prohibited around Florida and the Bahamas, the sharks are not staying within those regions. However, the researchers did discover that these shark species spent quite a bit of time within the U.S. EEZ and if the same protection which is afforded sharks in the waters around Florida state were extended to include U.S. federal waters then the practical level of shark protection would increase.

Owing to the fact that bull sharks are classified as Near Threatened in the IUCN Red List, tiger sharks as Threatened and great hammerheads as Endangered these species require immediate and urgent implementation of regulations which will afford them complete protection from fishing. Studies such as this can be used to inform policy makers and prove that extended protection zones are mandatory if the future of these species is to be assured.  

Graham, F., Rynne, P., Estevanez, M., Luo, J., Ault, J. and Hammerschlag, N. (2016) Use of marine protected areas and exclusive economic zones in the subtropical western North Atlantic Ocean by large highly mobile sharks http://onlinelibrary.wiley.com/doi/10.1111/ddi.12425/full