sharks

Sharks, The Apex Predators

Sharks, the Apex Predators of the Sea

Behind all conservation, there is appreciation. The most important tool for successful conservation is knowledge, a clear understanding of why you care in the first place. Sharks are a vital species for a healthy ocean, however this fact is often forgotten for dramatic impact in media publications. Understanding why their existence is crucial for our ocean cuts out any clouded judgement upon sharks that may previously exist. 

Sharks are Apex Predators

Sharks are top or “apex” predators in the marine ecosystem. This is because they have very few natural predators. A cascade effect naturally occurs in a balanced, healthy ecosystem, whether it be marine or terrestrial. Sharks as the apex predator, act as a regulator for biodiversity (Friedrich, Jefferson & Glegg, 2014, 3). They directly limit the abundance of species below them in the cascade or food chain. Sharks diets are especially varied, so that no one species of prey will become low in numbers through over predation (Friedrich et al, 2014, 3). If certain populations of prey are low, sharks are able to switch to another food source. This continues throughout the food chain, and is a sign of a healthy, biodiverse ecosystem. It is a naturally occurring event, which is greatly important, to provide a balance of species within the ecosystem itself. 

An Ocean Without Sharks 

Studies have shown that the greater abundance of sharks, the greater the diversity of species (Paine, 1966, 65). When comparing two reefs, one with sharks and one without, the latter circumstance showed species absences. Without sharks, there is a risk of over predation by the middle to lower predatory species with evidence of over eating of vegetation or primary producers (kelp, phytoplankton, or sea grass). Herbivorous preying species are in abundance with increased competition on food sources, called a “Top-Down” effect (Martin, 2009, 111). This results in surplus of middle predatory species, and overeating of the lowest species on the food chain which ultimately effects the species richness, and biodiversity upon the reef. If this was to occur on a larger scale, it could be catastrophic. The health of the ocean would decline, and seriously affect the way we live. 

Ocean Food Web Figure 1: Food web demonstrating sharks as the apex predator. Retrieved from Encyclopedia Britannica, Inc.

Ocean Food Web Figure 1: Food web demonstrating sharks as the apex predator. Retrieved from Encyclopedia Britannica, Inc.

Sharks have been on this planet for 450 million years, and are pretty amazing creatures. They come in many different types, from the gentle Whale shark (Rhincodon typus), to the notorious Great White (Carcharodon carcharias). Sharks are important for our ocean’s survival and need to be protected. There should be more concern of an ocean without sharks, rather than a beach with sightings and baited drum lines. As the apex predators of our largest ecosystem, sharks deserve our respect and our conservation efforts to protect them. 

Written by Jessica McCabe

 

 

Friedrich, L.A., Jefferson, R. & Glegg, G. (2014). Public Perceptions of Sharks: Gathering Support for Shark Conservation. Marine Policy, 47 :1-7. Doi: doi:10.1016/j.marpol.2014.02.003

Martin, R.A. (2009). Hunting Patterns and Geographic Profiling of White Shark Predation. Journal of Zoology, 279(2): 111-118. Doi: 10.1111/j.1469-7998.2009.00586.x 

Paine, R.T. (1966). Food Web Complexity and Species Diversity. The American Naturalist, 100 (910): 65-75. Retrieved from: http://oceana.org/sites/default/files/reports/Predators_as_Prey_FINAL_1.pdf

 

Image: Carnivore: Aquatic Food Web. (2011). [Art]. In Britannica Online for Kids. Retrieved from http://kids.britannica.com/comptons/art-55763

"Of Shark and Man" Review

Recently, we were given the wonderful opportunity to watch the feature length shark documentary Of Shark and Man. Below, you will find our review of it:

Of Shark and Man represents what all good documentaries should be; a heartfelt story told tastefully, artistically and has the immense capability to move you. David Diley does a fantastic job of balancing his own narrative, the story of Fiji and the story of the sharks of Fiji. He does it so well, in fact, that you do not realize there are three different stories going on, but instead one finely blended tale. 

Everything about this feature length documentary was perfect; the editing, the narratives, the cinematography, the underwater footage - all of it, seriously. David does a marvelous job of getting you interested in his own story by pulling you in with the abstract of Fiji and its' sharks, and finally... delivering fully with his own personal goals within the film, and it is exactly what the title hints at; of shark and man.

This film is not just your basic run of the mill shark documentary. No sir! A lot of documentaries have come out lately where all they are is semi-decent underwater shots, terrible voice overs and zero plot lines. Of Shark and Man smashes those films to bits, and the best part about all of that is that it didn't even try, it is just naturally that amazing and awe inspiring.

The music was like nothing I have ever heard before - it made me laugh, cry, worry and it made me dance, too! It is quite refreshing to hear such tastefully created music, which I may add, was influenced by the culture and way of life of Fiji. Way to keep your film authentic, David!

The way this film blends all of the stories into one beautiful (love) story is absolute poetry. Diley is a master of his craft, and this film is even more proof of his enormous talents! We had so many emotions running through us during the entire film (this is what a good feature length does! It moves you) - happiness, sadness, shock, fear, awe... you name it! 

In our very humble opinion, this film proves to be exactly what it promised to be - real, emotional and thought provoking. Well done David, you have yet again put your money where your mouth is and You, sir, have delivered!

Photo Credit Michael Patrick O'Neill

Photo Credit Michael Patrick O'Neill


Find out more about Of Shark and Man in the following links:

Their Website: http://www.ofsharkandman.com/

Their Facebook: https://www.facebook.com/OfSharkAndMan

Their Twitter: https://twitter.com/ofsharkandman

Also, check out Scarlet View Media: http://www.scarletviewmedia.com/

Our First Campaign of 2015 - Nursery Protection & Shark Monitoring Program: Dominican Republic

It is our absolute pleasure to announce our first (and official!) campaign of the 2015 year! 

"Sanctuary and Monitoring Program:  Dominican Republic"

The goal of this project is to finalize a set sanctuary in the city of Estero Hondo and to develop a local monitoring program for sharks in those waters. Our team is comprised of scientists, conservation leaders and award winning filmmakers. We will be working closely with the local populations to establish these goals.

Our project objectives would be:

  • Establish a finalized protection plan for nurseries used by sharks in the Dominican Republic.
  • Create a shark monitoring program with the locals in the areas to compile and keep data.
  • Document shark behavior through film and photo for conservation purposes.
  • Have ongoing local and international presentations about our work, our procedures and how this project is helping the locals and their economy.

We are in close and daily communication with government officials in the island and with many scientific researchers to make this project a total success. But, we cannot do this without YOUR help!

Hondo Estero, Dominican Republic

Hondo Estero, Dominican Republic

Please, help fund this very important campaign by following the link below. Any amount helps, and with every donation we get one step closer to our project goals. We understand that not everyone can support financially and this is why we also ask that everyone shares this blog post. The more people we reach, the higher our chances are of reaching our goals. 

Thank you for your ongoing support!

https://www.indiegogo.com/projects/sanctuary-monitoring-program-dominican-republic/x/9858106

Update: Projects, projects and more projects!

Hey there everyone! We figured we'd take a moment and update you all on what we've been up to these past couple of weeks:

  • Currently working on grant proposals for a conservation project we have going on in the Dominican Republic (More details to come soon!)
  • Working on an expedition to Mexican waters with the very talented bunch over at Pelagic Life; the plan is to film Blues and Makos.
  • Creating a small grassroots campaign in Hawai'i where the ultimately goal is to stop souvenir shops from selling shark teeth, bellies as "gifts"

Right now, these are our three main campaigns, but we are also doing many other things as well. We hope that you guys will continue to support us and as always, feedback is appreciated!

Lemon Shark

Sharks & Tonic Immobility

We investigate the tonic immobility phenomenon, whereby a shark falls into a hypnotic trance if it is turned upside down. Although useful for scientific research, is induced shark tonic immobility being abused?

Tonic immobility, by definition, is a state of apparent paralysis that animals enter usually in response to a threat, although it has also been correlated with mating in sharks. Virtually nothing is known about its underlying neurological and physiological processes in sharks. When inducing TI, the shark is flipped straight on its back and held in that position until it is turned back. Due to this knowledge, a lot of scientists have used it to their advantage, particularly for tag insertion and measurements of the sharks. The sharks do not move or try to get away. They stay in this catatonic state until they are inverted.

While it is okay in my personal and professional opinion to place sharks in TI for the sake of scientific research or for hook removals, it is not okay to place a shark in TI so that people (paying customers or individuals) can see how “cool” it looks or so that they can take photos of it being done. The sharks do not benefit from interactions like this and should not be subjected to such pointless stressful situations. As divers, it is our duty to dive responsibly and always be respectful of marine animals. Recently, there have been quite a few viral videos of people harassing (poking, prodding, riding, hugging, grabbing, etc.) sharks while diving because they saw it being done by other “professional” divers. Several videos have also surfaced and others have been around for a long time of dive operators placing sharks under TI so that their customers can take photos with the animals. This is not okay.

TI has been beneficial for scientists to have the animals in this state while still being able to keep them in the water. A few scientific studies have been conducted and the findings suggested that TI was correlated with a “…significant depression in blood pressure and heart rate…” (Davie, et al.) in black tip reef sharks. In another study conducted on juvenile lemon sharks, findings mentioned that TI “… induced a short term reduction in ventilatory efficiency…” and “animals maintained in TI were significantly hyperglycaemic compared to those that were not” (Brooks, et al.). Not a lot of research has been done on the effects of TI on sharks, but one thing can definitely be stated and that is that proper care should always be taken when using the technique during research, tagging, measurement or hook removal (to name a few positives) on the animals.

With each person trying to upstage the next, we are beginning to lose sight of why diving was a passion in the first place. It is possible to enjoy wildlife without harassing it; poking, prodding, riding and hugging are all forms of wildlife harassment. What we all need to understand is that just because we can do something, does not mean we should. As a species, we have slowly begun to forget what it is to respect other living creatures.

Sharks are majestic, mysterious and marvellous animals that should not be feared, but lack of fear should also not be synonymous with a lack of respect. When diving with sharks, we should always proceed with caution, respect and, ultimately, keep our hands to ourselves. Diving is a wonderful activity and so many people partake in it so often and seeing sharks underwater is always an incredible experience. Nothing beats being able to see sharks in the wild, behaving naturally; sharks do not need gimmicks to be one of the coolest animals on this planet, they do that all on their own.

 

References

Brooks, Edward J., Katherine A. Sloman, Stephanie Liss, Laila Hassan-Hassanein, Andy J. Danylchuk, Steven J. Cooke, John W. Mandelman, Gregory B. Skomal, David W. Sims, and Cory D. Suski. "The Stress Physiology of Extended Duration Tonic Immobility in the Juvenile Lemon Shark, Negaprion Brevirostris (Poey 1868)."Journal of Experimental Marine Biology and Ecology 409.1-2 (2011): 351-60. Print.

Davie, Peter S., Craig E. Franklin, and Gordon C. Grigg. "Blood Pressure and Heart Rate during Tonic Immobility in the Black Tipped Reef Shark,Carcharhinus Melanoptera."Fish Physiology and Biochemistry 12.2 (1993): 95-100. Print.

Henningsen, A.D., (1994). Tonic immobility in 12 elasmobranchs - use as an aid in captive husbandry. Zoo Biology, 13: 325-332