Are sharks apex predators? Does it matter?

We commonly refer to sharks as apex predators. Are they really? If they are not, does it matter? A few Australian researchers have come up with some answers to both questions.

First, are sharks apex predators? According to their findings, the answer is yes .... and no.

Example of an apex predator!

Here is what they found. "While size can be important in terrestrial ecosys- tems, size is crucial in marine ecosystems — which tend to be dominated by indeterminate organisms that grow continuously throughout their lives (Trebilco et al. 2013). Individual function changes due to onto- genetic diet shifts as organisms grow in size (Karpouzi

& Stergiou 2003, Pinnegar et al. 2003). The conse- quence is that size-structuring within communities, rather than species identity, is an important factor in determining the strength of competitive and predatory interactions (Dickie et al. 1987, Kerr & Dickie 2001). For example, studies have shown high overlap in diet between similar-sized sharks regardless of maturity state and species identity (e.g. Bethea et al. 2004). Therefore, designation of marine species into apex and mesopredator categories should consider the life stage and size of individuals."

I'm not a scientist, but what I'm getting is, size matters!

But so, why should we care? We are not scientists, (well, you may be, but I'm not) so what does a classification matter? 

Here is what they have to say to that. 

Example of a meso predator!

"Our size-based view of the classification of predatory roles raises important questions about what objectives to manage, and how these objectives can be best achieved. Protection of reef communities through marine protected areas (MPAs) or fisheries regulation (or indeed, naturally on those few locations far from human population centres) would ensure the mesopredator sharks on these reefs are sheltered from fishing pressure. However, the same may not be true for apex predators because their broad movement patterns and large home ranges (Meyer et al. 2009) would expose them to a greater diversity of fishing fleets and gears, and thus a greater overall mortality than the smaller-ranging, reef-dwelling mesopredators. Hence, the apex pred- ators of coral reefs may be silently eliminated by offshore pelagic longline fisheries, unbeknownst to those managing reef diversity and function (Cox et al. 2002). Therefore, reef-based MPAs are not adequate to protect these species"

So basically they are saying that we need to do more than establish MPAs to adequately protect apex predators.

Here is a graphic that may be a bit more clear on the subject.
 

This graphic shows, that without MPAs prey species would greatly increase, while both mesopredators and apex predators decrease. With reef scale (small, local) MPAs, the mesopredators thrive, keeping the prey species in balance, but the apex predators still decline.

 

In practical terms, this means that we have to protect apex predators on a much larger scale than the less migratory mesopredators. In order to do that, we need to know both where they are and when they are there. With that knowledge we can push for local and/or seasonal protection for these migratory apex predators. In order to get that data, we need data that shows the migratory behavior of the various species of apex predators. 

You can read the entire paper here.

Cheers,

Martin Graf

CEO

Shark Diver

About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at staff@sharkdiver.com

Worlds Largest Marine Reserve? Yes!

Great news for all of us who love the Great White Sharks and all the other creatures that live in the Ocean! The New York Times reports that  Australia Plans World’s Largest Marine Reserve.

According to the report:

Australia plans to create the world’s largest network of marine reserves, encompassing a 3.1 million square kilometer patchwork of coastal waters, the government announced Thursday. The move is aimed at balancing protection for the country’s delicate reefs and marine life, which are facing growing environmental pressures, with the demands of its booming resource-driven economy.

Shredder, swimming at Guadalupe Island

It's great to see that Australia takes a major step to protect the marine environment. The article further states; fishing and oil and gas exploration would be restricted in nearly one-third of Australia’s territorial waters, an area of 1.2 million square miles that includes the pristine Coral Sea off the country’s northeastern coast and the iconic Great Barrier Reef.

Read the complete article

We at Shark Diver  are applauding  Australia for this action and hope that it will encourage other countries to follow suit.

Cheers,


Martin Graf
Dive Operations Manager
Shark Diver/Horizon
Isla Guadalupe, Mexico

“Now we know that while white sharks across Australia can mix, the intriguing thing is that they seem to return to either east or western regions to breed,” Bruce said.

Source: redOrbit (http://s.tt/1durs)

“Now we know that while white sharks across Australia can mix, the intriguing thing is that they seem to return to either east or western regions to breed,” Bruce said.

Source: redOrbit (http://s.tt/1d

About Shark Diver. As a global leader in commercial shark diving and conservation initiatives Shark Diver has spent the past decade engaged for sharks around the world. Our blog highlights all aspects of both of these dynamic and shifting worlds. You can reach us directly at sharkcrew@gmail.com.

Chile creates a Marine Reserve around Sala y Gómez

Chile’s President Sebastián Piñera announced the creation of Sala y Gómez Marine Park, a no-take marine reserve of 150,000 square kilometers around Sala y Gómez island.

Sala y Gómez is an uninhabited island that’s part of a biodiverse chain of seamounts that are vulnerable to fishing activity. Dr. Enric Sala, marine ecologist and National Geographic Ocean Fellow, called Sala y Gómez “one of the last undisturbed and relatively pristine places left in the ocean.”

Last March, Oceana, National Geographic and the Waitt Foundation conducted a preliminary scientific expedition to the island and found abundant populations of vulnerable species such as sharks and lobsters, much larger than in the depleted ecosystem in nearby Easter Island, which is not protected from fishing. In addition, the scientists found unexpectedly high biodiversity in deeper waters.

After the expedition, Oceana and National Geographic presented a proposal to President Piñera advocating the protection of the entire exclusive economic zone, a total of 411,717 square kilometers around the island. The Fisheries Committee of Chile’s Senate supported the recommendation unanimously.

The new park expands Chile’s total marine protected area more than 100 times, from 0.03% to 4.41%. Currently less than 2% of the global ocean is protected, although the Parties of the UN Convention on Biological Diversity – including Chile – agreed to protect 10% of their exclusive economic zones by 2012.

Shark Legacy Project - Honduras 100% Shark Fishing Ban Enacted

They say big things come in small packages. In the shark world nothing is bigger then governments who enact bans on shark fishing in their waters.

Palau's recent shark fishing ban and the Maldives decision to ban shark fishing in their waters was met with acclaim both in the tourism and shark conservation worlds.

As it turns out other governments were watching, and taking note.

Thanks in part to the Shark Legacy Project headed up by a small and dedicated team in Roatan, Honduras the government just announced they will ban all shark fishing in Honduran waters while they study the issue of shark fishing and the economics of Honduran sharks which, for a Latin American country, is a simply stunning decision.

The next steps will require resources and help from the shark tourism industry and from the research side as well to make this ban a permanent and regional example.

From Peter Wilcox Director of the Shark Legacy Project:

"Thanks Patric - have a major victory down here. After our meetings with DIGIPESCA they pushed up the passing of a bill that has now gone into practice. It puts a moratorium on the fishing of all shark species in all the waters of Honduras! Think that makes Honduras the first in the Caribbean to have a shark sanctuary! Part of the drive behind this measure was to cease use of sharks as a resource until research can be done to evaluate the population/species of sharks here. So finally, a government willing to step in before the problem gets unmanageable. We met with the government this last weekend to discuss how we can assist in this research (as you may be able to guess they do not have much in the way of funding for their own research). We are travelling to Tegucigalpa this week to discuss further research and affiliations to benefit the goals of protecting sharks here."

We would Like to congratulate the Shark Legacy Project and all those who have worked to this point to get the ban in place.

This is very good conservation news indeed.

Shark Diving Industry - Threats of Violence?

The last report we ever expected to see coming from the Maldives and the South Ari Atoll, home of an excellent regional whale shark research program, might involve commercial operations in the area threatening violence at knife point.

From the Dhivehi Observer this week tales of "ugliness on the high seas" as commercial operations come into conflict with regional researchers over whale shark gold.

This is not a new tale, shark diving operations that are in conflict with each other are the stuff of legends within the commercial shark diving industry. Up until today these conflicts usually stayed quiet and never appeared on the front page:

"MV Orion and MV Southern Cross crews have allegedly threatened to ram rival boats and stand accused of throwing heavy dive weights at tourists and dhoni crews from nearby Diva Resort. Most shockingly, in January, the crew of MV Southern Cross boarded a dhoni belonging to the Maldives Whale Shark Research Programme, foreign researchers who monitor the sharks. The MV Southern Cross crew threatened at KNIFE POINT to kill the researchers unless they quit the area."

For the record we fully support the efforts of the Maldives Whale Shark Program and have done so for a few years. Small minded industry ugliness is not a new phenomenon. Calling it out for public consumption is.

The owner operators of both the MV Orion and MV Southern Cross must be made to understand that user groups have rights to animals as much as they do. A smart minded operation would seek ways to incorporate research into the fabric of its dive and marketing efforts, a win-win solution to user group conflicts under the banner of conservation shark diving.

Hopefully these well known dive operators will realize their errors before it is too late and commercial whale shark diving in Maldives becomes tainted by irreparable scandal.

Maldives Whale Shark Research Programme - Report

The DC Rainmaker Blog has an in depth first person report of whale shark research in the Maldives this week.

We had the pleasure of meeting the DC Rainmaker folks at Isla Guadalupe during the filming of Shark Diver: The Movie in 2009.

"The Maldives Whale Shark Research Programme (with an ‘e’ at the end, British style…) was founded in 2006 by a group of marine biologists looking to setup a permanent facility in the Maldives to study whale sharks. Unlike many other areas of the world, it appears a bunch of the whale sharks actually stick around the Maldives year round, providing an excellent opportunity for long term research. Though they don’t quite yet have the financial resources to stay year round, the goal is to be able to rotate teams and individuals to the island for sustained continuous research."

Full report, great read and Kudos guys!

Tiger Shark Killer Charged in South Africa

In a quick reaction to unprecedented pressure from groups world wide South African authorities raided the home and then charged a man today for the killings of 8 Tiger sharks.

Aliwal Shoal Marine Protected Area on the KwaZulu-Natal south coast was the site of the recent shark slaughter, witnessed by shark eco tour operations and surfers.

"Conservationists are furious not only because is it illegal to catch tiger sharks in the protected area, but Aliwal Shoal is one of the top dive sites in the world."

As we commented in our blog on this subject a week ago, Marine Protected Areas are the key stone to protecting sharks. As unofficial site guardians, shark diving companies are often the first to report misdeeds at the hands of those who would harm sharks for either sport or profit.

The staff of Shark Diver remain committed to ongoing reporting of these important stories. With sharks being slaughtered by the millions each year and populations falling worldwide it might well be these few protected areas that save entire species in the years to come...if we can protect the sharks in them.