Sharks in the Bahamas


Image coutersy of Gishani Heaton (gishani.sqsp.com). Dr Owen R. O’Shea taking a blood sample from a Caribbean Reef Shark, Carcharhinus perezii.

 

The Bahamas boasts some of the best shark diving experiences in the world, and is also a unique country in which to study sharks. Dr. Owen O’Shea is a shark biologist from the Cape Eleuthera Institute (CEI) in the Bahamas. Among several projects, he is currently running the deep-water shark research program as well as teaching deep-water ecology to students at The Island School – the sister organisation to CEI. Dominic Bryant asked Dr. O’Shea a few shark-related questions while surveying in the Bahamas for the Catlin Seview Survey.

 

What type of sharks do you find in the Bahamas?

They call the Bahamas ‘shark country’ and with good reason. The Bahamas comprises over 700 islands, islets and cays, which create a unique environment for both coastal, oceanic and deep-water shark species. The Bahamas has coral reef associated species such as Caribbean reef sharks, tiger sharks and black-tip sharks. Vast mangrove creeks dominate many of the larger islands supporting lemon and nurse shark populations while the pelagic environment of the Atlantic Ocean supports transient populations of oceanic white-tip sharks, mako sharks, blue sharks and hammerheads. 

We have recently begun deep-water surveys just off shore of the Cape Eleuthera Institute and have recorded several deep-water species including Cuban dogfish, rough-skin dogfish, two species of gulper shark a false cat shark, blunt-nose and big-eye six gills and seven gill sharks.  The diversity of sharks in the deep sea exceeds that of the shallow water.

 

What role do sharks have within the coral reef ecosystems?

Sharks are apex predators, which means they are the top of the food chain and through predation, regulate the community structure of lower trophic levels. They remove weak and sick fish allowing the fittest of prey populations to propagate. This process is known as top-down control and is essential for balance and health in marine ecosystems.

 

What are the biggest threats towards sharks today?

Some species of shark are undergoing the greatest population decline in modern history of a group of species. This is due largely to overfishing where public demand for fins has exponentially grown over the past 50 years. Fins are seen as a delicacy and status symbol in many Asian countries and commercial fisheries are keeping up with demand by removing an estimated 100 million sharks from the oceans each year. In addition, Chinese medicine uses gill filaments, oil and cartilage to promote remedies for common ailments, but the truth is that no scientific evidence exists to support these claims.

 

What is the current status of the shark population in the Bahamas?

The Bahamas is a very special place – it is only one of a handful of nations globally to have enforced a shark protection that includes all recreational as well as commercial harvest. While The Bahamas has had a commercial ban on shark harvest since 1993 which has seen increases in the abundance of certain species, total ‘shark park’ status will undoubtedly build on this foundation. 

 

 

The full interview with Dr. Owen O'Shea follows:

1. What is your role at the Cape Eleuthera Institute (CEI)?

I am Research Associate with the Shark Research and Conservation Program (SRCP) and a teacher for research classes within the Island School. I am responsible, in part for coordinating our research assistants, technicians and interns. Currently, I am running our deep-water shark research program as well as teaching deep-water ecology for Island School classes. Presently we have several research projects either underway or in planning, and with my colleague, Dr. Edd Brooks, I am responsible for overseeing their completion and communication of results, via manuscript preparation and national and international conferences.

 

2. What type of sharks do you find in Bahamas?

The Bahamas is an island nation comprised of over 700 islands, islets and cays, which in turn create a unique environment for both coastal, and oceanic shark species. The Bahamas has coral reef associated species such as Caribbean reef sharks, tiger sharks and black-tip sharks. Vast mangrove creeks dominate many of the larger islands supporting lemon sharks and nurse sharks, while the pelagic environment of the Atlantic Ocean supports transient populations of oceanic white-tip sharks, mako sharks, blue sharks and hammerheads.  We have recently begun deep-water surveys just off shore of the Cape Eleuthera Institute and have recorded several deep-water species including Cuban dogfish, rough-skin dogfish, two species of gulper shark a false cat shark, blunt-nose and big-eye six gills and seven gill sharks.  The diversity of sharks in the deep sea exceeds that of the shallow water.

 

3. What role do sharks have within coral reef ecosystems?

Sharks are apex predators, which means they are top of the food chain and are thought to regulate community structure through predation. They remove weak and sick fish allowing the fittest of prey populations to propagate. This process is known as  ‘top-down’ control and is essential for balance and health in marine ecosystems.

 

4. What are the biggest threats towards sharks today?

Some species of shark are  undergoing the greatest population decline in modern history of a species. This is due largely to overfishing where public demand for meat and fins has exponentially grown over the past 50 years. Fins are seen as a delicacy and status symbol in many Asian countries and commercial fisheries are keeping up with demand by removing an estimated 100 million sharks from the oceans each year. In addition, Chinese medicine uses gill filaments, oil and cartilage to promote remedies for common ailments, but the truth is that no scientific proof exists to support these claims.

 

5. What about sharks make them vulnerable to these threats?

Sharks, as a group of fishes along with their relatives – rays and chimeras – are susceptible to extrinsic pressures because they have conservative life history characteristics. This means that they are long lived, grow slowly, reach sexual maturity later than most fish, and bear few young. These traits not only increase vulnerability, but also may exacerbate population recoveries under certain circumstances. Sharks simply cannot reproduce fast enough to replace animals removed by fishing.

 

6. The Bahamas has the reputation of being “shark country”, how and why do you think the Bahamas has gained this reputation?

The Bahamas is a very special place – it is only one of a handful of nations globally to have enforced a protection level to sharks that includes all recreational as well as commercial harvest. While The Bahamas has had a commercial ban on shark harvest since 1993 which has seen increases in the abundance of certain species, total ‘shark park’ status will undoubtedly build on this foundation.  Other nations include Palau, Maldives and Tokelau that have decreed live sharks are worth more in their lifetime through dive tourism, than a dead shark which will often fetch no more than $50USD at market. Bahamas boasts some of the best shark diving experiences in the world, and therefore is also a unique country to study sharks. It is, however, important to point out that the Bahamas shark sanctuary, as with all shark sanctuaries, only protect species which remain within its borders.  Many species, such as the oceanic whitetip and tiger shark, are highly migratory and are undoubtedly being targeted by commercial fisheries in other parts of their range.

 

7. What are the main shark conservation methods employed in the Bahamas and CEI?

The SRCP at CEI was founded in 2006 with a single small grant to build some baited remote underwater video survey units.  Over the last seven years it has grown rapidly to a point where it now has ongoing research projects in every major ecosystem found in the greater Caribbean region.  These projects include measuring the impact of longline capture on a number of commercially important species, the use of critical coastal habitats such as mangrove creeks by juvenile lemon sharks and nurse sharks, and the basic ecology of a number of local species including the Caribbean reef, tiger and lemon sharks. In addition we are also actively working on the physiology of the yellow stingray, working on a new type of baited video survey designed to quantify the distribution and abundance of rarer species of shark, and of course the deep water project which also uses baited surveys. We undertake a number of satellite tracking studies in particular focusing on the oceanic whitetip shark which is considered critically endangered in the western Atlantic, and more recently the Caribbean reef shark.  In addition the SRCP will be deploying similar tags onto bull sharks at the end of 2013. Bull sharks have defined and predictable patterns of visitation to the near-shore waters of CEI at certain times of year, but their summer whereabouts at other times of the year are unknown.

 

8. One of the first things I noticed when we arrived in Freeport was the “shark free marina” sign. How effective do you think these marinas are for shark conservation?

I think this is an excellent and proactive way to advertise the intentions and beliefs of the Bahamas and its citizens towards shark conservation. To prevent trophy hunters from posing with their dead ‘rewards’ in an archaic and frankly offensive manner on the sides of docks is a good thing. Sharks are revered and still held in mystical fascination by the public, but there are better ways to share in their beauty and awe, rather than seeing them hung upside down on boardwalks in marinas. A far greater challenge for a recreational fisherman is to catch tag and release a shark in good condition, thus contributing to the understanding and conservation of their target species.  Catching and killing a shark is pretty easy by comparison.

 

9. In your opinion what is the status of shark populations in the Bahamas, when compared to rest of the Caribbean and the world?

The banning of commercial longline fishing 20 years ago has seen the sustainability of somewhat healthy shark population in the Bahamas. Of course, other nations bordering the Bahamas offer challenges for this trend when we have certain species occupying more than one EEZ. Comparing Bahamian shark populations to the rest of the world is difficult, but in my research experience, the lack of commercial fishing, and now total blanket bans on any type of shark harvest, can only validate that we have one of the strongest, and naturally representative shark abundances in the world.

 

10. How could human induced climate change, affect shark populations in the Caribbean?

This is a difficult question that I am merely speculating on. Climate change can raise ocean temperatures and increase acidification through increases in CO2 absorption.  This has been shown to degrade reef-building corals and affect the equilibrium of healthy coral reefs, which are among the most biologically diverse ecosystems on the planet. Shallow, tropical marine environments are characterized and dominated by coral reefs, which are in turn controlled by the presence of apex predators. Studies show decreases in biodiversity are correlated with decreases in coral density. This leads to algae dominated systems, which are competitively superior to coral reefs, and therefore harder to revert and recover from. This would have a direct impact on the abundance of sharks on reefs and so if this were to occur on any larger scale within the Caribbean, it is likely we may see declines in shark abundances. 

 

12. Finally could you tell us your most memorable shark experience in the water?

Good question! I have had so many memorable experiences with sharks in the water –all exhilarating - but I would have to say my most memorable was the first time I came face to face with the biggest fish on the planet – the whale shark. It swam straight up to me and it really didn’t look real – it appeared to be made of plastic, as I couldn’t fathom swimming with something so large. I ended up swimming with four that day and to share a personal space with a creature so large and docile is certainly my shark highlight.

 

I would like to thank Owen for his time in answering these questions, I know I have personally gained a greater understating of shark conservation and research in the Bahamas through reading them. 

LOADING