Marine protected area helps shark populations recover from fishing

Publication specs

Title: Evidence for rapid recovery of shark populations within a coral reef marine protected area

Authors: Conrad Speed, Mike Cappo, Mark Meekan

Journal: Biological Conservation

Year: 2018

The diminishing number of sharks around the world is no longer a topic of interest just for scientists and fisheries managers. Many people who rely on these animals as resources – whether as food or for ecotourism operations – are becoming aware of the menacing situation facing certain shark populations due to overfishing, shark finning, habitat loss, and climate change. Until now, there has been little evidence that marine protected areas benefit sharks in coral reef habitats. Thanks to Paul G. Allen Philanthropies, the first results coming from our sampling provide insight into the recovery of grey reef sharks and apex predator species like the tiger shark and lemon shark at a remote atoll in the Indian ocean.

Ashmore reef is situated 350km northwest of Australia’s mainland, and has been an enforced no-take marine protected area (MPA) since 2008. Although the official establishment of the Ashmore Reef National Nature Reserve was in 1983, only occasional monitoring of the area was happening until 2008 when a government vessel became stationed there 300 days out of the year. Prior to the inception of the MPA, there was legal and illegal targeted shark fishing. In 2004, researchers from the Australian Institute of Marine Science (AIMS) conducted baited remoted underwater video surveys (BRUVs) at Ashmore Reef. The AIMS research team then returned in 2016 to repeat the study as part of our global survey of sharks and rays on coral reefs around the world.

This provided the ideal set-up to study Ashmore Reef shark populations before and after full protection. Findings show:


The relative average number of grey reef sharks (measured as the maximum number of individuals per camera drop; MaxN) increased from about 0.16 individuals per hour in 2004 to approximately 0.74 individuals per hour in 2016.



The proportion of reef sharks (grey reef sharks, blacktip reef sharks, and silvertip sharks) in the assemblage increased from 28.6% in 2004 to 57.6% in 2016.28.6%  57.6%


The proportion of apex species (tiger sharks, lemon sharks, scalloped hammerheads, and fossil sharks) in the assemblage increased from 7.1% in 2004 to 11.9% in 2016.


 7.1%  11.9%


This study is not only our project’s first publication, it is also one of the first of its kind in a coral reef ecosystem to highlight that enforcement in a marine protected area aided shark population recovery and at a rate much faster than previously predicted by demographic models.

Protecting migrating shark species isn’t always easy

Publication Specs

Title: Conservation challenges of sharks with continental scale migrations

Authors: Michelle R. Heupel, Colin A. Simpfendorfer, Mario Espinoza, Amy F. Smoothey, Andrew Tobin and Victor Peddemors

Journal: Frontiers in Marine Science

Year: 2015

It’s no surprise to anyone that sharks can move. What may be surprising is that some shark species can move thousands of kilometers, traveling across multiple jurisdictions. When sharks swim across state, national, and international boundaries they are exposing themselves to varying levels of threats and protections. In order for conservation measures to be effective for mobile species, knowledge of the scale of movement is required.

Bull sharks are no strangers to long-distance movements, being known to travel hundreds of kilometers. On the Australian East coast, researchers studied bull shark movements across two state jurisdictions: Queensland (QLD) and New South Wales (NSW) using acoustic telemetry. Tracking devices were surgically inserted into 114 bull sharks, which then transmitted their signals to fixed receivers. When a tagged shark swam past the receiver, data on that individual was stored and later retrieved.  


On average, the bull sharks were found to travel 1194km with no evidence of individuals making movements based on the time of year. The sharks were detected on multiple receivers at various sites, which is evidence that these sharks are connecting temperate and tropical systems while also crossing state boundaries.


Larger juveniles and adults were found to swim the furthest, with multiple hypotheses for this behavior:

  • The shift in diet from juvenile to adulthood
  • The need to reduce competition for food
  • To avoid eating their own kin
  • Less tolerance for nearshore freshwater
  • A combination of all of the above

Since bull sharks are frequently moving along the eastern coast of Australia, current marine protected area zoning may have limited benefits for this species. Managers face complex challenges when making conservation decisions that affect highly mobile shark species. This study highlights the need for jurisdictional cooperation between QLD and NSW that would lead to effective marine protected area zoning, which could include movement corridors for bull sharks. Nonetheless, managers face difficult decisions in terms of negotiation and coordination with different governments when trying to protect species that move across state, national, and international boundaries. Studies like this one will improve our knowledge of shark movements in order to facilitate the decision-making process that will lead to effective conservation measures.

How marine protected areas support healthy coral reefs

Publication specs

Title: Marine protected areas increase resilience among coral reef communities

Authors: Camille Mellin, M. Aaron MacNeil, Alistair J. Cheal, Michael J. Emslie, M. Julian Caley

Journal: Ecology Letters

Year: 2016

Many of our researchers are SCUBA divers, and we like to think that many of our followers also enjoy spending time under the sea or at the very least learning about it. It’s no wonder that we enjoy diving on vibrant reefs with a diversity of species. Of course, we also love getting the opportunity to see sharks and stingrays on our dives.

However, not all reefs are healthy. This has led scientists and advocates to push for more ocean protection. Marine protected areas (MPAs) are designed to support and protect the balance of life within them, making them valuable ocean conservation tools. Yet, their efficacy has been debated among scientists. 

Recently, a study was conducted using 20 years of data inside and outside marine protected areas of the Great Barrier Reef (GBR). A total of 46 locations were surveyed: 26 sites with fishing activity, and 20 sites without fishing activity. MPAs offered protection from natural disturbances like coral bleaching and disease, storms, and crown of thorn sea star outbreaks. On healthy reefs, crown of thorn sea stars feed on fast growing corals. However, outbreaks of these invertebrates can have devastating effects on the reef – crown of thorn sea stars accounted for 42% of coral loss from 1985 – 2012 on the GBR.

Researchers found that inside MPAs the effect of the disturbances was 30% lower and the recovery of the community was 20% faster than outside MPAs. On average, recovery time within MPAs took only six years compared to nine years outside these protected reefs. So why did reef sites in MPAs remain strong through disturbances and recover faster after disturbances? The study offered several potential explanations:        

  • Increased feeding on macroalgae, which allowed young coral to settle.





  • Increased predation on coral-eating fish like butterflyfish.



  • Lesser impact of crown of thorn sea stars resulting from more predation on them within MPAs.
  • Multiple species performing their ecological function together as a community.

Without these protected areas, researchers predicted that the recent loss of coral cover in the GBR might have been much worse. This study both recommended and demonstrated the value of MPAs that prohibit fishing.