Publications

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.

Lessons from coral reef “bright spots”

Publication specs

Title: Bright spots among the world’s coral reefs

Authors: Joshua E. Cinner, Cindy Huchery, M. Aaron MacNeil et al.

Journal: Nature

Year: 2016

Millions of people depend on healthy coral reef ecosystems for food security and their livelihoods. This study analyzed data from 2514 coral reefs from 46 countries to understand how reef fish biomass is related to socioeconomic drivers and environmental conditions. “Bright spots” and “dark spots” were compared. Bright spots are not simply remote areas with low fishing pressure. These authors determined that bright spots can also be areas with high human population densities and resource use. Likewise, dark spots can be remote relatively untouched coral reefs. So what’s working in these bright spots and what are communities living near bright spots doing right?

After surveying local experts near bright spots, the authors discovered what maintains these healthy coral reef ecosystems:

  • cultural practices such as customary taboos (e.g. customs prohibiting the extraction of certain species) and marine tenure
  • a high level of local engagement in management
  • high dependency on marine resources
  • deep water refuges

Alternatively, researchers found what characterized dark spots:

  • intensive fishing using capture and storage technologies such as nets, motorized boats, and freezers
  • recent environmental shock such as coral bleaching events and cyclones

Learning lessons from bright spots will be essential for protecting these areas and improving the health of coral reef dark spots. Policies should be focusing on socioeconomic drivers of dark spots like market forces. Focusing on such drivers will help identify sustainable practices that could aid conservation efforts in these areas.

Tracking tiger sharks

Publication specs

Title: Crossing Latitudes – Long-Distance Tracking of an Apex Predator 

Authors: Luciana C. Ferreira, Michele Thums, Jessica J. Meeuwig, Gabriel M. S. Vianna, John Stevens, Rory McAuley, Mark G. Meekan 

Journal: PLOS One

Year: 2015

Although some people may picture sharks as intimidating predators that roam long distances, that’s not the case for many of the more than 400 species. There are also small sharks and those that spend most or part of their lives in one area – a pattern known as residency. When it comes to tiger sharks, the big scary predator vision is at least partially true – they are large (sometimes more than 5m in length), can be frightening if you’re a turtle, and swim long distances (potentially up to 8000km). However, using satellite tags, this study showed some tiger sharks along the coast of Western Australia to actually be seasonal residents to the coastal waters near where they were initially tagged. The eight sharks spent about half their time in marine reserves. The sharks tended to prefer warmer coastal waters, but the results from these data demonstrated that they have the ability to migrate between tropical waters and cool temperate waters (as cold as 6°C – brr!).

Understanding tiger shark movements is important. Where sharks go influences population connectivity. In order to manage populations, we must first understand where individuals are – and in Western Australia, they are spending parts of the year along the coast near where the researchers deployed the tags. Tiger sharks in Shark Bay were shown to influence the behavior and movements of prey, so it’s no surprise that the tiger sharks likely have a sort of structuring effect on the ecosystem. Protecting sharks locally, along with both their habitat and prey, is vital.

One female tiger shark, tagged at Ningaloo Reef, had the longest duration track to date for a tiger shark (517 days) and moved 4000km in that time period. After being tagged, she moved to Rowley Shoals then impressively made it to Indonesia and back into Australian waters (a distance of about 1000km) in just two weeks. This movement pattern is known as site fidelity – where the animal makes a long-distance movement and then returns to the location where it was tagged. International cooperation between Indonesia and Australia will be needed to make informed conservation decisions since there was documented movement between both countries. For this tiger shark, local protection in Western Australia is not quite enough.

 

A predator’s role in storing carbon

Publication specs

Title: Predators help protect carbon stocks in blue carbon ecosystems

Authors: Trisha B. Atwood, Rod M. Connolly, Euan G. Ritchie, Catherine E. Lovelock, Michael R. Heithaus, Graeme C. Hays, James W. Fourqurean, Peter I. Macreadie

Journal: Nature Climate Change

Year: 2015

When you think about carbon (C) storage in an ecosystem, you may think about a lush tropical forest sucking up carbon dioxide from the atmosphere. What isn’t considered as often is coastal marine ecosystems, which take up C 40 times faster than tropical forests. An estimated 25 billion tons of C is buried in vegetated coastal habitats like seagrass meadows, mangroves, and salt marshes, making them the most C rich environments in the world. Degrading these “blue carbon ecosystems” releases C into our atmosphere, fueling climate change. But did you know that losing predators like sharks within these environments also indirectly leads to the release of C?

One example of this comes from Western Australia where sharks influence how often herbivores like dugongs and sea turtles feed in a given time period. These grazers like to eat in places where there are very few tiger sharks waiting to attack them. In habitats where sharks are present, they spend more time watching their backs. This means that less seagrass is being consumed, and in some cases is only being cropped. In the areas where sharks are present and there are fewer grazers, the seagrasses are mostly slow growing species, which promotes the storage of C since it is not breaking down quickly. In other words, where the abundance and behavior of herbivores are being controlled by predators, growth of vegetation is enhanced, which leads to increased storage of C.

Scientists don’t know the total global area affected by the loss of predators. However, if only 1% of the vegetated coastal areas were to be affected, about 460 million tons of C would be released, equivalent to the emissions from 97 million cars. In order to protect these blue carbon ecosystems, balanced conservation efforts will need to occur where the habitat, predators, and herbivores are protected together.

These single ladies don’t need a man

Publication specs

Title: Facultative parthenogenesis in a critically endangered wild vertebrate

Authors: Andrew Fields, Kevin Feldheim, Gregg Poulakis, Demian Chapman

Journal: Current Biology

Year: 2015

The Internet exploded last year with news of a vertebrate capable of producing offspring without sex. Billions of people across the globe tuned in to learn about the smalltooth sawfish’s newly discovered ability. The study was led by our lead principal investigator, Dr. Demian Chapman, and his Ph.D. student, Andrew Fields. This ability, scientifically known as facultative parthenogenesis, where animals that generally need a male to produce offspring can do so without one, is not a new scientific concept. In fact, it has been discovered in many captive vertebrates like birds, reptiles, sharks, and more recently rays. So what’s so novel about it? Smalltooth sawfish are a type of batoid, or ray, that are critically endangered and in 2007 were among the first elasmobranchs to receive international trade regulations by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Since the 1960s, these rays have seen a population decline of about 95% due to habitat loss, overfishing, bycatch, and target capture – where their rostrum, or snout, was sold as curio, aka a bizarre object usually used for home decoration. Smalltooth sawfish are currently only found in Southwest Florida and parts of the Bahamas. This study provided the first evidence of facultative parthenogenesis in the wild and it may be more common than previously thought, particularly in populations on the verge of extinction. But don’t get too excited – there is no scientific evidence of this phenomenon occurring in mammals.

Global patterns of shark and ray bycatch

Publication specs

Title: Global patterns in the bycatch of sharks and rays

Authors: Shelby Oliver, Matias Braccini, Stephen J. Newman, Euan S. Harvey  

Journal: Marine Policy

Year: 2015

The left-behind, the unwanted, the unmanaged – whatever you want to call it, bycatch is prevalent in commercial fisheries. Sharks and rays are at risk of becoming bycatch in all commercial fisheries. So what exactly is bycatch? Bycatch is the discarded (dead or alive) catch and/or unmanaged catch from fisheries. While fishing for particular species, fishers often catch unwanted species using longlines, trawls, gillnets, and purse-seines. It is common for these so-called undesired species to be illegally kept and later sold, particularly in the case of some sharks and rays, whose fins sometimes end up in the lucrative fin trade.

This study reviewed relevant data from global commercial fisheries. Most of the data came from the North Atlantic Ocean, which is not where the majority of fishing occurs. This suggests that most fisheries are not effectively reporting bycatch data. Shark bycatch mainly occurred in the South Atlantic pelagic longline fishery. No patterns were found in ray bycatch, likely due to a lack of data reporting. For both sharks and rays, the largest total annual bycatch took place in pelagic longline and deep sea/coastal trawl fisheries. One shark species dominated longline bycatch – the blue shark, pictured above – which may make up more of the catch than the actual target species. Rays are not exempt from unregulated fishing, and as a group are considered more threatened than sharks. Perhaps even more alarming is that the majority of ray bycatch comes from commercial trawl fisheries where they are often thrown back into the ocean, left for dead. 

Below is an overview of the prevailing species caught as bycatch by region:

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Sharks

  • Blue sharks – North & South Atlantic, Western Pacific
  • Silky & thresher sharks – Indian Ocean & Eastern Pacific

Rays

  • Pelagic rays – South Atlantic, Western Pacific & Indian Ocean

Sharks

  • Sharpnose sharks – North Atlantic
  • Dogfish – South Atlantic, Eastern & Western Pacific
  • Carpet sharks – Indian Ocean

Rays

  • Skates – North & South Atlantic


Sharks

  • Blacktip shark – North Atlantic
  • Sevengill sharks & shortnose spurdogs – Indian Ocean
  • Catsharks – Eastern Pacific

Rays

  • Cownose rays – North Atlantic
  • Bat rays – Indian Ocean & Eastern Pacific


Sharks

  • Coastal sharks (e.g. blacktip, bull, and dusky sharks) – North Atlantic & Eastern Pacific
  • Silky sharks – South Atlantic & Indian Ocean

Rays

  • Manta & devil rays – South Atlantic, Eastern Pacific & Indian Ocean


These results suggest that global shark and ray bycatch monitoring – data collection and availability – should become high priority for management. Sharks and rays are important fishery and tourism resources, especially in developing nations, so it is vital to find out if these levels of bycatch are sustainable for each species. Should the current levels of shark and ray bycatch in commercial fisheries not be sustainable, regulations would have to be modified or developed and enforced to safeguard their future.

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.  

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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.

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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.

 

parrotfish

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  • Increased predation on coral-eating fish like butterflyfish.

 

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  • 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.      

Shark sanctuaries need enforcement

Publication Specs

Title: Indicators of fishing mortality on reef-shark populations in the world’s first shark sanctuary: the need for surveillance and enforcement
Authors: Gabriel M.S. Vianna, Mark G. Meekan, Jonathan L.W. Ruppert, Tova H. Bornovski, Jessica J. Meeuwig
Journal: Coral Reefs
Year: 2016

When you think of a shark sanctuary what do you imagine? Perhaps a beautiful coral reef that is a blue haven for sharks? Hold that thought while we take a moment to examine reality through the eyes of science.

A recent study in Palau evaluated the world’s first shark sanctuary using underwater visual surveys. This shark sanctuary covers an area of 629,000km2 and was declared in 2009 to try to stop foreign long-line vessels from finning sharks. However, this study demonstrated that illegal, underreported, and unregulated shark fishing is still present within the sanctuary, particularly in remote offshore areas. In these areas, there was an abundance of lost fishing gear and there were fewer and smaller sharks than close to shore.

Sometimes marine protected areas, like shark sanctuaries, get a bad rap as “paper parks”, or protected areas that are essentially just written on paper because they lack the enforcement required to truly protect species living within them. Palau may have created an important management tool, but they are lacking the resources required to follow through on regulations. This study also sheds light on the fact that without baseline data on shark populations within the proposed protected zones, it becomes difficult to monitor their effectiveness over time. If we truly want a blue haven for sharks, the research demonstrates that enforcement within shark sanctuaries is an urgent need. The country’s government is currently expanding enforcement efforts within the shark sanctuary.

Dining in fear: the influence of predator and prey behavior on the health of coral reef ecosystems

Publication specs

Title: Reefscapes of fear: predation risk and reef heterogeneity interact to shape herbivore foraging behaviour
Authors: Laura B. Catano, Maria C. Rojas, Ryan J. Malossi, Joseph R. Peters, Michael R. Heithaus, James W. Fourqurean and Deron E. Burkepile
Journal: Journal of Animal Ecology
Year: 2015

Imagine: you’re quietly enjoying your breakfast when suddenly a lion barges through your front door. Do you continue eating? Run for cover? The answer for you, and other potential prey, is pretty clear. For small, plant-eating fish living on coral reefs, this is a constant threat. So much so that even just the fear of a potential predator, like sharks and grouper, can alter their behavior. While that may seem obvious, a recent study has revealed something not quite so intuitive – this fear is actually good for the entire coral reef ecosystem.

The findings of this study suggest something rather surprising – without predators, herbivorous fish cannot fulfill their normal function on the reef. Reefs come in a variety of structures and are comprised of a multitude of interdependent organisms. The feeding behavior of these fish, like surgeonfish and parrotfish, are influenced by both the structure of the reef and their predators. In the absence of predators, or in this case a grouper decoy, the fish ate almost two times more seagrass than when the decoy was present. In areas with and without complex reef structure, the fish did not eat as much when the grouper decoy was present.

Complex reef habitats don’t offer easy escape or shelter, which means that in areas with predators lurking, fish spend more time trying to find safe spaces rather than grazing. According to these findings, herbivorous fish concentrate their feeding to areas where they are less likely to encounter a roving predator, leaving more space for coral to settle, grow, and thrive. Reefs without predators encourage grazing across larger areas, leaving less open space for young coral to survive. This study suggests that this interplay – between predator, prey, and ecosystem – is crucial for healthy reefs.

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